March 10, 2009

Physics, quants, and the crash

Posted by Arcane Gazebo at 11:25 PM

I am pretty much required to blog about this piece in the New York Times entitled "They Tried to Outsmart Wall Street": "they" being physicists who left science for Wall Street. And the not-so-subtle implication of the title is that we failed to outsmart Wall Street (and possibly wrecked the economy in the process). To that I say, in the words of Bart Simpson: it was like that when I got here.

More seriously, while I have no doubt that there were crappy quant models out there that contributed to the current crisis by maximizing short-term gain over long-term risk, this was true all the way up and down the chain and the quants don't deserve any more of the blame than anyone else. Quants respond to incentives the same way everyone else does, and the compensation structure on Wall Street can incentivize immediate profit and deferred risk. (My employer is trying to curb this effect by instituting a clawback provision on bonuses; I don't know how widespread this is, but it seems like a good idea to me.)

The Times article is curiously focused on ex-physicists, as if quants don't come from any other fields. In my ten months on the Street I've met quants from a broad range of science and engineering fields, and physicists aren't a majority. That might be a peculiarity of my department's hiring practices, with physicists being much more common elsewhere, but I'd be surprised. Anyway, Kevin Drum noticed this too and wonders why physicists are so suited to quant roles. He has a theory that it's the culture:

Even among the number crunching set, physics has a reputation as the most aggressive, male dominated branch of geekdom: only 14% of physics PhDs are women, the lowest of any of the sciences. (Math is pretty male dominated too, but pales compared to physics: 29% of math PhDs are women.) If the first thing that "aggressive and male dominated" reminds you of is the big swinging dick world of high finance, give yourself a gold star. Call this the testosterone theory: physicists are attracted to Wall Street because they like the atmosphere.

I don't think this is right: the atmosphere in a typical physics department is nothing like the stereotypical Liar's Poker trading floor that Drum is alluding to. To the extent that the environment I work in is like academia, it's because I'm lucky enough to work with a group run by ex-academics rather than people with a typical trader's background. Instead, what Drum calls the "affinity theory" really is the right one. The work I do now is a lot like the problems I worked on as a physicist. It's not just (as Drum suggests) about math; it's about the ability to work with huge data sets and make sense of them, and to find signals in a noisy system. This is a much bigger factor than testosterone levels.

September 10, 2008

Still alive

Posted by Arcane Gazebo at 7:39 PM

Today at work we were discussing the self-styled "simplest weather report ever", umbrellatoday.com. Also useful is the similarly-designed hasthelargehadroncolliderdestroyedtheworldyet.com (via a GChat status message). Personally, I keep meaning to quote Buffy the Vampire Slayer's Oz on the subject: "But we know the world didn't end, 'cause... check it out."

In my new career the big question to ask is not whether the world will end, but whether one can make money off people's belief that it will. Intrade doesn't seem to have a futures contract on whether the LHC will destroy the Earth, but you can buy or sell the discovery of the Higgs boson.

Of course, if you are trying to destroy the Earth, and you've lost confidence in the LHC, you might find your Plan B at this page.

February 18, 2008

Quantum Construction

Posted by Arcane Gazebo at 3:19 PM


quantum construction, originally uploaded by arcanegazebo.

I spotted this sign while running in Berkeley this morning, and had to go back for a photo. From the slogan it looks like they're promoting energy-efficient home design, which is commendable; thus they probably want "quantum" to indicate "technologically advanced". But of course, "quantum" also brings to mind uncertainty, which maybe isn't what a contractor wants to associate themselves with. At the very least, I would expect Quantum Construction to be able to give a precise time estimate, or a precise cost estimate, but not both.

However, I assume their creation operators are top-notch.

Permalink | Tags: Berkeley, Photos, Physics, Quantum Information, Science

December 18, 2007

Done!

Posted by Arcane Gazebo at 12:54 PM

I filed my dissertation this morning; I am now Dr. Arcane Gazebo. (Well, technically the degree isn't conferred until Thursday when the semester ends, but whatever.)

The main result of the entire thesis comes down to a single plot, shown below. This isn't the "explain my thesis" post so I'll just say that the plot shows our ability to control the coupling energy between two qubits by applying a bias current to our readout device, hence the thesis title Solid-State Qubits with Current-Controlled Coupling. The solid curves are calculations based on device parameters and the dashed curves are one-parameter fits.

Now these points of data make a beautiful line...

If anyone needs me this evening, I'll be at Triple Rock.

Permalink | Tags: Academia, Life, Physics, UC Berkeley

June 5, 2007

Frank Tipler {TECH}s up the Bible

Posted by Arcane Gazebo at 5:01 PM

When I was in high school, a physicist named Frank Tipler published a book called The Physics of Immortality. The book purported to show that modern cosmology was not only compatible with Christianity, but predicted something like Christian theology including the concept of an afterlife. At the time I was still a believer, and was becoming interested in physics, so I was curious to see what the book had to say.

It was bad—really bad. So much so that even with only a high school knowledge of physics, and a predisposition to accept its conclusions, I found it ridiculously implausible. It wouldn't even have made it as bad science fiction (although Charlie Stross borrowed the concept in a more interesting way in Iron Sunrise). Years later, taking Caltech's intro astronomy course, I had the pleasure of hearing the professor deliver a very unflattering digression on Frank Tipler.

I was reminded of all this when I found out (via Sean Carroll) that Tipler has a new book out: The Physics of Christianity. And it sounds even sillier, if possible. It seems that Tipler is now interested in explaining various Biblical miracles though physics, for example: (from Victor Stenger's review)

In the case of Jesus walking on water, protons and electrons in the normal matter in a layer of water under his feet are annihilated. The neutrinos produced go off invisibly downward with high momentum, the upward recoil enabling Jesus to keep from sinking.

This is actually similar to what you see in other The Physics of... books, such as in The Physics of Harry Potter's explanation of how the Sorting Hat could be implemented with SQUID sensors. But those books are, as Sean Carroll points out, just fun exercises in comparing fictional worlds to the real world. On the other hand, Frank Tipler is trying to explain supposed actual historical events, and it's hard to see what the point is of making up some story about a hypothetical decay process underpinning various miracles. Does it really change anyone's understanding, believer or not, to go from "Jesus could walk on water because he's omnipotent" to "Jesus could walk on water because he could annihilate protons with electrons on demand, because he's omnipotent"? It doesn't do any explanatory work.

And so what all this suggests to me is that Frank Tipler thinks the Bible should be more like Star Trek. A while back I found this post on an RPG-related blog, which explains how technical language gets inserted into Star Trek scripts:

I am told that the writers of Star Trek scripts do not usually come up with all of the jargon that the characters use. Instead, they just make the notation {TECH} wherever the characters should say something technical, and someone else will come along to fill in each such instance with some chunk of technobabble. This has an important story consequence: since the science is completely arbitrary, it's necessarily the case that the plot can't really hinge, in a compelling way, on the technical and scientific choices the characters face. It's all just {TECH}, and at best technobabble can provides sci-fi color, and at worst it's an excuse for a deus ex machina resolution.

So I imagine that Frank Tipler reads the Bible and sees a bunch of {TECH} notations that he feels compelled to fill in himself. And the last sentence of that quote describes the effect pretty well, which is why even as a believer I found Tipler's book unsatisfying.

Permalink | Tags: Christianity, Physics, Psychoceramics, Religion

May 6, 2007

Bad quantum press releases: this time, it's personal

Posted by Arcane Gazebo at 10:19 PM

Scott Aaronson points out an overly-excited press release from NEC, which claims: "NEC, JST and RIKEN successfully demonstrate world's first controllably coupled qubits". This was indeed an exciting development when we published it five months ago. At best NEC has the world's fourth controllably coupled qubits.

That said, the stupidity seems to be limited to the press release, and the paper actually looks pretty interesting, apparently with time domain results that no one else has shown. (I haven't been on the campus network today so I haven't had a chance to read more than the abstract.)

Permalink | Tags: Physics, Quantum Information, Science

April 24, 2007

A pretty accurate re-enactment

Posted by Arcane Gazebo at 3:22 PM

I took my qualifying exam this morning. If you'd like to know it went, click here.

Permalink | Tags: Academia, Comics, Physics

April 12, 2007

No new neutrinos

Posted by Arcane Gazebo at 3:59 PM

The Standard Model wins another round: the MiniBooNE experiment, searching for neutrino oscillations to confirm or disconfirm the anomalous LSND result, found no new physics. Heather Ray explains in a guest post at Cosmic Variance.

Given the author's last name, her use of "awesome-o" in a section heading is suspicious.

Permalink | Tags: Physics

April 9, 2007

Colloquium blogging: Lawrence Krauss on the future of the universe

Posted by Arcane Gazebo at 8:55 PM

Today's colloquium speaker was Lawrence M. Krauss, who is somewhat well-known for doing a lot of public outreach and having written several books aimed at the general public. (One of these books was The Physics of Star Trek, which I received from three or four separate people as birthday gifts when it came out in 1995.) He's also done political advocacy, perhaps most notably fighting "intelligent design" creationism in Ohio. Today's colloquium was about neither Star Trek nor politics, however, but about the "dismal future" of the universe.

The talk was basically a series of extrapolations from the fact that cosmological observations show a universe that is not only expanding, but expanding at an exponentially increasing rate. The most direct consequence is that eventually everything that isn't gravitationally bound to our galaxy cluster will be receding away at faster than the speed of light, not only inaccessible but invisible. This won't happen for many billions of years, so it's not of any particular concern to us personally, but will be an issue for the future of life itself. As a result of being isolated to a single cluster, the amount of energy available becomes limited: I think the estimated number was 3x1067 Joules, for what it's worth. Consequently, the amount of information that can be processed also is limited, to on the order of 10120 bits. One of the more interesting numbers quoted was that, if one assumes that Moore's Law will continue to hold on the rate of information processing, civilization would run through this capacity in just 400 years. (Since at the moment we are limited to the amount of energy here on Earth, I expect Moore's Law will fail rather sooner than this, which is why I'm skeptical about Singularity talk.)

Another section of Krauss' talk was devoted to what cosmology would look like to a far-future civilization in one of these "island universes" created by expansion. Since these future scientists would be unable to observe the universe outside the cluster, they would be unable to infer the expanding universe or the Big Bang, and would conclude that the universe was static. (They could, however, estimate the age of the universe from abundance of various elements.)

Finally, on long timescales everything disappears, as dark matter halos evaporate and galaxies dissipate.

Krauss, being a more public figure than most physicists, was a very good speaker who gave an entertaining talk. He was deliberately provocative, declaring at the beginning that he would alienate most of the audience, and particularly targeted advocates of the anthropic principle. I was hoping for more fireworks in the question session, but it was somewhat tame. A video of this talk will appear at some point here on the department website.

Permalink | Tags: Colloquia, Physics

March 7, 2007

March Meeting, Days 2 and 3

Posted by Arcane Gazebo at 9:06 PM

I thought about posting last night but this was pre-empted by the fact that the slides for my talk were unfinished (and also the Clarke group dinner). First I want to register a complaint:

hund's rules for conference seating

This is how physicists (or maybe everybody) fill seating at conferences. The first people to arrive take the seats on the outside of the rows, and then fill in to the middle. This is really annoying when arriving in the middle of the session and having to climb over a bunch of people to get into the one empty seat. I am aware that this is a really lame complaint, but please, fill from the middle!

Now that I've got that out of my system: the last couple days were a blur of superconducting qubit talks. There's a lot going on in this field, and most groups had three or four (10-minute) talks in a row to have enough time to explain all their results. One experiment I thought was very neat was this one from Terry Orlando's group at MIT. In flux qubits like the ones we study, one can measure the temperature by sweeping the flux bias across the degeneracy point and measuring the population of the qubit states. Higher temperatures will give wider curves, as energies further away from the degeneracy point are more likely to be populated by thermal activation. When we measure this on our qubits we usually get something like 150 mK, mysteriously somewhat higher than the fridge temperature (roughly 50 mK).

What the Orlando group did was to apply an analog of laser cooling (as in atomic physics) to their qubit, using a microwave pulse to induce transitions that ultimately cool the system. As a result they were able to see these temperatures (as measured from the widfh of the qubit step) reduced by a factor of 100, from 300 mK to 3 mK. It was pretty impressive; I'm not sure how important it is for quantum computing or whether it's something we should be doing with our qubits, but it's a nice application of techniques from another field.

This morning I gave my talk, which was helpfully introduced by Frank Wilhelm's talk immediately prior, in which he said something like "the really important development for scalability is what Travis Hime will talk about next". So the pressure was on, but I think I did ok. After this was... more qubit talks, but I was mostly decompressing after finishing mine and didn't pay as much attention as usual.

Tomorrow I go to see talks by other Clarke group members, including John himself. And then, an evening flight back to Berkeley.

Permalink | Tags: Academia, Physics, Quantum Information, Science

March 5, 2007

March Meeting, Day 1

Posted by Arcane Gazebo at 9:50 PM

bear peering in glass

Actually I spent much of today working on my talk instead of going to sessions. The superconducting qubit sessions start tomorrow morning and basically run continuously until Thursday evening. I did go to some talks in the afternoon, though, mostly in D2: Ion Traps for Scalable Quantum Computation. (In some sense this is our competition.)

Ike Chuang, who is a big name in this field, gave the first talk, which laid out the challenges in making a practical quantum computer with ion traps. Most of this dealt with error correction; according to Shannon's theorem (or maybe a quantum information version thereof) it should be possible to build an error-free quantum computer out of qubits that do make occasional errors, as long as the failure rate is below some threshold. Unfortunately in some cases they've looked at this requires a prohibitively large number of operations, as many as 1020. One can try to implement various error-correcting codes, such as Shor's or Steane's, but certain operations that are needed for a universal quantum computer don't work within these codes. And in fact Chuang et al. have shown that there is no stabilizer code that allows a universal set of operations to be performed within the code—one has to decode first before performing at least one of the operations.

The other talks in the session were less abstract, and thus harder to understand (since I'm not terribly familiar with this architecture). The talk by Slusher described a proposal for a VLSI-based scalable ion-trap based quantum computer, which seemed impressive, except I'm pretty sure this is the one Chuang mentioned that would require 440 watts of laser power to operate.

I skipped out on the last talk to go to D8: Superconductivity: STM of Cuprates and see what the group I worked in as an undergrad was up to. However, I haven't thought about STM of cuprates for a while now and only had the faintest idea what they were talking about.

A tempting alternative for the end of the day was Session D33: Focus Session: Quantum Foundations II. It starts out as a perfectly normal session, but somewhere around 4:30 becomes the dumping ground for crackpots. For example:

D33.00014 : Do Particles have Barcodes?

If an elementary particle shown in Fig 2 of gr-qc/0507130 has an UNSTABLE quantum connection to the rest of the universe calibrated by nature in terms of Planck times, as also proposed in my separate MAR07 abstract, there exists a possibility that each particle has a barcode of its own. Instability implies varying periods of connections and disconnections of particles to the universe, which would be equivalent to the varying widths of white and black strips of commercial barcodes. Considering the high order of magnitude of Planck times in a second, each particle and the universe generated by its radiations may have their unique birth times registered in their barcodes. My quest for the cause of consciousness, in MAR06 abstracts, as an additional implication of physics/0210040, leads to the inquiry if these unique parallel universes are like the ones that give rise to consciousness as proposed by some physicists. With all due respect, the attempts to explain TOE of inert matter may not be attempts to explain one step to climb up on a stairway at a time. They may be attempts to explain only half a step at a time to on a stairway made with only integer number of steps. The search for TOE assumes such a theory exists. Mathematics has no barrels to fire bullets that can shoot down a non-existent bird. A Hamiltonian knows no consciousness, a missing ingredient of biology made of particles or vice versa, and of realistic TOE.

The talk after that one describes a theory of Atonic Physics [sic], which sounds like an outtake from Monty Python's bookstore sketch.

Permalink | Tags: Academia, Physics, Quantum Information, Science

February 28, 2007

Your search requests answered

Posted by Arcane Gazebo at 7:09 PM

Today's amusing search request: should I make an outline slide for my APS march meeting talk?

My physics category archive is the second hit for this search in Google. This is a surprising query to see from (presumably) a physicist: an overspecific question phrased in standard English is not the most well-formed Google search. (Some search engines are designed to take queries in this form, but Google is not one of them.) Nevertheless, the searcher lucked out: the fifth hit is a set of slides on giving good scientific talks.

I'll answer the question anyway in case anyone else is wondering. If it's an invited talk, the answer is almost certainly yes—a 30-minute talk will cover enough different points that an outline at the beginning will help the audience follow the transitions. If it's a contributed talk, with only ten minutes of material it may not be necessary. If the talk divides nicely into multiple distinct sections, it's a good idea, but if it's centered on a single result you probably don't need it.

Permalink | Tags: Academia, Physics, Search Requests

February 27, 2007

Quantum mechanical Tomb Raider

Posted by Arcane Gazebo at 1:44 PM

Terence Tao explains quantum mechanics by analogizing to video games (particularly Tomb Raider):

Now, how does the situation look from Lara’s point of view? At the save point, Lara’s reality diverges into a superposition of two non-interacting paths, one in which she dies in the boulder puzzle, and one in which she lives. (Yes, just like that cat.) Her future becomes indeterministic. If she had consulted with an infinitely prescient oracle before reaching the save point as to whether she would survive the boulder puzzle, the only truthful answer this oracle could give is “50% yes, and 50% no”.

This simple example shows that the internal game universe can become indeterministic, even though the external one might be utterly deterministic. However, this example does not fully capture the weirdness of quantum mechanics...


He goes on to make some macabre modifications to the game mechanics in order to improve the analogy, bringing in interference and entanglement. It's an entertaining post, but it gets truly ridiculous in the comments where he devises a Tomb Raider level to test Bell's Inequality.

Permalink | Tags: Games, Physics, Quantum Information

February 26, 2007

Cults and hierarchies in physics

Posted by Arcane Gazebo at 3:52 PM

There's a great post at Cosmic Variance about the cult of genius in physics:

During high school or college, many aspiring physicists latch onto Feynman or Einstein or Hawking as representing all they hope to become. The problem is, the vast majority of us are just not that smart. Oh sure, we’re plenty clever, and are whizzes at figuring out the tip when the check comes due, but we’re not Feynman-Einstein-Hawking smart. We go through a phase where we hope that we are, and then reality sets in, and we either (1) deal, (2) spend the rest of our career trying to hide the fact that we’re not, or (3) drop out. It’s always bugged the crap out of me that physicists’ worship of genius conveys the simultaneous message that if you’re not F-E-H smart, then what good are you?

I remember clearly the moment I found that physics was much harder than I realized (although I had no delusions of being F-E-H smart by that point anyway): it was Ph 106a. I was used to being able to pick up concepts fairly quickly, but the subtleties of advanced classical mechanics (and Goldstein's textbook) eluded me, and it was a serious blow to my confidence that I really didn't get it. I worried that this was a sign that all the high-level physics concepts would be beyond my reach. Obviously that turned out not to be the case; I just needed to work a lot harder to understand these concepts. It's striking to me how rapidly the difficulty seemed to ramp up, but this may have been due to the way Caltech structured the physics curriculum rather than an inherent property of the subject.

Chad Orzel has a related point:

Too many people approach physics as if there's some sort of Great Chain of Being, with the most abstract theoretical particle physics at the very top and low-energy experimentalists down at the bottom, just above biologists and rude beasts incapable of speech.

This drives me right up the wall.

There's no inherent moral worth to working on more "fundamental" and mathematical physics. A lack of familiarity with algebraic topology is not a defect in character, or a sign of gross stupidity. Low-energy physics is different than high-energy theory, but not inferior to it.


This is something I noticed a lot as an undergrad—in my freshman class almost everyone who wanted to do physics was interested in high-energy theory; I was rare in actually being inclined towards experiment at that point. Part of it is that there's a certain glamour to working on the Theory of Everything, and there's an apparent elegance to a simple but widely applicable theory that makes the experimental world look messy and ugly by comparison. (Although in fact the Standard Model isn't really what I'd call simple or elegant.) Furthermore, at roughly the freshman undergrad level the major contact with experimental physics is through high school or freshman physics labs, which tend to be pretty lame.

(So how did I end up wanting to do experiment at that stage? At the end of my senior year in high school I had the opportunity to do some labs on more advanced topics, and they were less structured than what I was used to—instead of the procedure being laid out explicitly, I was given a set of equipment and had to figure out how to use it to measure a certain parameter or figure out how something worked. Although it was still pretty far removed from the actual practice of experimental physics, it gave me a better sense of the kind of problem-solving involved, which I found I really enjoyed. Plus I noticed I was better at it than I was at theory.)

Permalink | Tags: Academia, Caltech, Physics

February 20, 2007

T-Rex and superfluidity

Posted by Arcane Gazebo at 7:05 PM

This post by Mason inspired me to make a Dinosaur Comic:

Noninertial theology (Image is behind the link because it's too wide for the blog template.)

The thesis in question was by Richard Packard, who is a Berkeley physics professor. I can only hope decades from now somebody will be writing Dinosaur Comics about my thesis.

Permalink | Tags: Comics, Physics, Randomness

February 12, 2007

Sixteen Qubits (starring Molly Ringwald)

Posted by Arcane Gazebo at 11:30 AM

There's been some buzz lately about D-Wave's sixteen-qubit quantum computer that they're planning to demonstrate tomorrow. Instead of writing a post on this I'm just going to link to (and endorse) Scott Aaronson's post on the subject. There's a lot of skepticism about D-Wave in the community.

Permalink | Tags: Physics, Quantum Information, Technology

February 1, 2007

Dusty physics history in the LeConte Hall attic

Posted by Arcane Gazebo at 4:02 PM


leconte attic, originally uploaded by arcanegazebo.

This was my Project 365 photo for Tuesday, but I wanted to do a blog post on it as well.

The attic of Berkeley's main physics building resembles nothing so much as an inert and dusty version of the Jawa caravan in Star Wars. Filled with vintage '70s/'80s (and older) electronics and cryogenic equipment, it contains the history of decades of cutting-edge research, now consigned to storage. Also, annoyingly elusive items that have to be accounted for in the annual lab inventory.

I was up here Tuesday afternoon looking for a particular frequency synthesizer that LBL's records say we own. It turns out there is a frequency sythesizer up here, in among our group's poorly-delineated junk pile, but it is a slightly different model (presumably with a bad motivator). I didn't find the instrument I was looking for, but did take a few pictures, which all turned out blurry since there was hardly any light and the camera couldn't acquire focus.

Perhaps the most unusual instrument is the one that's musical rather than scientific: an old organ sitting in the corner, presumably for aspiring Phantoms of the Opera.

Permalink | Tags: Photos, Physics, UC Berkeley

January 25, 2007

Contact the patent office!

Posted by Arcane Gazebo at 6:34 PM

Over coffee I and another grad student had a brilliant innovation: an electric guitar with SQUID pickups! Due to the high sensitivity and low noise of the SQUID, we expect the sound quality to be extremely good. Of course, the guitar will have to be filled with liquid nitrogen (we're assuming high-Tc SQUIDs here) or equipped with a cryocooler. The LN2-filled guitar would have the advantage of producing plumes of fog on demand, and would be especially spectacular when smashed against the stage at the end of the show.

Permalink | Tags: Music, Physics, Randomness

December 29, 2006

2007 March Meeting Abstract

Posted by Arcane Gazebo at 12:22 PM

The program for the 2007 APS March Meeting is now up. I have an invited talk this year; unfortunately it's in an early morning session. Here's the abstract:

Session N2: Progress in Superconducting Quantum Computing

8:00 AM–11:00 AM, Wednesday, March 7, 2007
Colorado Convention Center - Four Seasons 4

Sponsoring Units: GQI DCMP
Chair: Robert Schoelkopf, Yale University
Abstract: N2.00002 : Solid State Qubits with Current-Controlled Coupling
8:36 AM–9:12 AM

Author: Travis Hime (University of California, Berkeley)

The ability to switch the coupling between quantum bits (qubits) on and off is essential for implementing many quantum computing algorithms. We have demonstrated such control with two, three-junction flux qubits coupled together via their mutual inductances and via the dc SQUID (Superconducting Quantum Interference Device) that reads out their magnetic flux states. The flux in each qubit was controlled by an on-chip loop, and the chip was surrounded by a superconducting cavity that eliminates fluctuations in the ambient magnetic field. By applying microwave radiation to the device, we observed resonant absorption in each of the qubits when the level splitting in the qubit matched the energy of the microwave photons. With the qubits biased at the same frequency, the interaction produced an avoided crossing in their energy spectrum. At the avoided crossing transitions to the first excited state were suppressed and transitions to the second excited state enhanced, indicating formation of singlet and triplet states in the coupled-qubit system. The observed peak amplitudes were consistent with calculated matrix elements. When both qubits were biased at their degeneracy points, a level repulsion was observed in the energy spectrum. A bias current applied to the SQUID in the zero-voltage state prior to measurement induced a change in its dynamic inductance, reducing the coupling energy controllably to zero and even reversing its sign. The dependence of the splitting on the bias current was in good agreement with predictions. This work was performed in collaboration with P.A. Reichardt, B.L.T. Plourde, T.L. Robertson, C.-E. Wu, A.V. Ustinov, and John Clarke, and supported by NSF, AFOSR, ARO and ARDA.

On a related subject, I still intend to write a post about the results in our Science paper, but I haven't got around to it yet.

Permalink | Tags: Physics, Science

November 30, 2006

Publication: Solid-State Qubits with Current-Controlled Coupling

Posted by Arcane Gazebo at 2:29 PM

As some of you know, we recently had a paper accepted to Science. The paper appears in the latest issue, and is now available online.

I will try to post something in the next few days that explains these results for the non-physicists in the audience. In the meantime, there's this post from March about these experiments (from before we had the major findings), and here's the abstract:

Solid-State Qubits with Current-Controlled Coupling

T. Hime, P. A. Reichardt, B. L. T. Plourde, T. L. Robertson, C.-E. Wu, A. V. Ustinov, John Clarke

The ability to switch the coupling between quantum bits (qubits) on and off is essential for implementing many quantum-computing algorithms. We demonstrated such control with two flux qubits coupled together through their mutual inductances and through the dc superconducting quantum interference device (SQUID) that reads out their magnetic flux states. A bias current applied to the SQUID in the zero-voltage state induced a change in the dynamic inductance, reducing the coupling energy controllably to zero and reversing its sign.

Permalink | Tags: Lab, Physics, Publications, Quantum Information, Science

October 3, 2006

Berkeley Physicist wins Nobel

Posted by Arcane Gazebo at 8:50 AM

UCB cosmologist George Smoot won the Nobel Prize for Physics today, for his discovery of anisotropy in the cosmic microwave background. He shares the prize with John Mather of NASA Goddard. Here's Berkeley's press release, the Nobel press release, and the AP article.

UPDATE: This, of course, was the Science: It Works, Bitches measurement whose data appeared in xkcd.

UPDATE II: Other bloggers writing about the prize: Sean at Cosmic Variance, Chad at Uncertain Principles, Steinn at Dynamics of Cats, Stefan at Backreaction, Andrew Jaffe, Rob Knop at Galactic Interactions, Janet Stemwedel at Adventures in Ethics and Science (whose mother worked with COBE and shares some anecdotes).

Maybe I'll try to get some pictures at the champagne reception later today...

UPDATE III: From the physics department reception, when Smoot is asked to make some remarks (this is paraphrased):

Smoot: I've been making statements all day... but now I can say what I'm really thinking, because there's no press.
[Berkeley Chancellor] Birgeneau: There's always press.
Smoot: Yeah, I'm worried about bloggers.

Wouldn't want to disappoint... I did forget my camera, though.

Permalink | Tags: Physics, Science, UC Berkeley

September 29, 2006

LHC as a black hole generator

Posted by Arcane Gazebo at 3:04 PM

Backreaction has a substantial and intriguing post about the production of micro black holes in particle accelerators (particularly the LHC). It's a test for extra dimensions: in three-dimensional space it's not possible to generate enough energy to create a black hole with a particle accelerator, but for theories of gravity involving extra dimensions, gravity gets stronger at short distances and this enters the realm of possibility. WIth crude approximations it's possible to estimate that the LHC could produce one black hole per second.

This isn't dangerous, since tiny black holes evaporate almost instantly through Hawking radiation. In fact, it's a nice way to measure some properties of extra dimensions if they exist. However, it's a problem for collider experiments in that information about small length scales becomes inaccessible.

The whole post is worth reading; it's pretty cool even if supervillains looking for a Doomsday Device won't find it useful.

Permalink | Tags: Physics, Science

September 25, 2006

Newsweek on the gender gap at Berkeley

Posted by Arcane Gazebo at 1:36 AM

Newsweek has an article on the gender gap in science, and looks at Berkeley's physics department in particular:

To get a sense of how women have progressed in science, take a quick tour of the physics department at the University of California, Berkeley. This is a storied place, the site of some of the most important discoveries in modern science—starting with Ernest Lawrence's invention of the cyclotron in 1931. A generation ago, female faces were rare and, even today, visitors walking through the first floor of LeConte Hall will see a full corridor of exhibits honoring the many distinguished physicists who made history here, virtually all of them white males.

But climb up to the third floor and you'll see a different display. There, among the photos of current faculty members and students, are portraits of the current chair of the department, Marjorie Shapiro, and four other women whose research covers everything from the mechanics of the universe to the smallest particles of matter. A sixth woman was hired just two weeks ago. Although they're still only about 10 percent of the physics faculty, women are clearly a presence here. And the real hope may be in the smaller photos to the right: graduate and undergraduate students, about 20 percent of them female. Every year Berkeley sends freshly minted female physics doctorates to the country's top universities. That makes Shapiro optimistic, but also realistic. "I believe things are getting better," she says, "but they're not getting better as fast as I would like."

Overall the description of Berkeley is positive; they highlight some of the female researchers here and mention policies that the campus is undertaking to improve the situation.

Permalink | Tags: Academia, Physics, Science, UC Berkeley

September 2, 2006

Clarke group research in Physics Today

Posted by Arcane Gazebo at 7:35 PM

I'm late noticing this, but the August issue of Physics Today has an article (subscription required) about axion detection experiments, which mentions some work being done in the Clarke group:

An amplifier whose noise temperature approaches the quantum limit would dramatically improve the sensitivty and search rate of the axion experiment. To achieve that goal, our collaborator John Clarke and his coworkers at the University of California, Berkeley, developed a new amplifier based on a microstrip-coupled superconducting quantum interference device in 1996. Unlike the noise behavior of heterojunction transistor amplifiers at low temperatures, the intrinsic noise of the SQUID is proportional to the physical temperature, the origin being thermal noise in shunt resistors across the SQUID's Josephson junctions. Cooling reduces the noise until it flattens out within 50% of the quantum limit. Newer SQUID designs with micro-cooling fins that enhance the coupling of electrons to the lattice are pushing these devices closer still to the quantum limit.

Unfortunately the full article is only available to subscribers, but those of you who are APS members can check it out. The quantum-limited amplifier is pretty cool and some groups are looking at using it for qubit experiments as well. Ironically, the vacuum pumps required to cool this low-noise amplifier are really loud, and so having to work in the same room as this experiment is sort of annoying.

Permalink | Tags: Lab, Physics, Science

August 24, 2006

"Qual Season!" "Prelim Season!" "Qual Season!" "Prelim Season!"

Posted by Arcane Gazebo at 6:40 PM

Gordon Watts and Chad Orzel have some thoughts on qualifying exam season. This confused me until I realized that what other departments call the qual is what Berkeley's physics department calls the preliminary exam. Incoming grad students take the written prelims as soon as they arrive: these are a pair of six-hour exams given on consecutive Saturdays, one on classical physics and one on modern physics. After passing the written exams, one then takes the oral prelims which are an additional two hours (again divided evenly between classical and modern). One must pass the whole fourteen-hour suite before joining a research group.

This is every bit as stressful as the links above describe; the grading is set up so that only about two-thirds of the students pass each round, and officially you only get three tries. (In fact, almost everyone passes by the third attempt.) I don't really have any advice for the written portion, but for the orals I had my faculty mentor give me a practice run that was incredibly helpful (especially since I got asked many of the same questions in the actual exam).

We do have something called a qualifying exam; it's a two-hour oral exam set up on an individual basis, and meant to be taken after two years in research. The first hour is a presentation by the student of a proposed topic for the dissertation, and the second hour is an exam on the subfield relevant to this research. As it happens, I will be taking the qual "soon". Some of you may note that I have been doing research for four years, and have been about to take the qual for two years now. Indeed, it is quite common for students to put off the qual until just before writing the dissertation, where the "proposal" actually becomes a presentation of results. Most departments call this the "thesis defense".

On the other hand, we don't have a thesis defense, so it all evens out in the end.

Permalink | Tags: Academia, Physics, UC Berkeley

A different Monte Carlo method

Posted by Arcane Gazebo at 6:00 PM

A recent preprint appearing on the arxiv:

Do superconductors violate Lenz's law? Authors: J.E. Hirsch

When a magnetic field is turned on, a superconducting body acquires an angular momentum in direction opposite to the applied field. This gyromagnetic effect has been established experimentally and is understood theoretically. However, the corresponding situation when a superconductor is cooled in a pre-existent field has not been examined. We argue that the conventional theory of superconductivity does not allow a prediction for the outcome of that experiment that does not violate fundamental laws of physics, in particular Lenz's law. Instead, an unconventional theory of superconductivity predicts an outcome consistent with the laws of physics, through the creation of angular momentum. We discuss how to test these assertions experimentally.


The argument, which I'm not sure I buy, relates to the angular momentum in the body of a superconductor when magnetic fields are expelled in the Meissner effect. But the author challenges me to put money behind my skepticism with this:
Comments: Readers are invited to place a wager on the outcome of the proposed experiment, this http URL

Yes! Now you can gamble on experimental physics! Next: bribing experimentalists to throw the results.

Permalink | Tags: Games, Physics

Rough Superconductor

Posted by Arcane Gazebo at 3:53 PM

Niobium is a metal that we frequently use here for its superconducting properties (Tc = 9.3 K). At lunch today we were wondering where it comes from: are there niobium mines somewhere? Perhaps, I suggested, it is mined in Africa under highly exploitative conditions, and we'll find protestors picketing the lab for our use of blood niobium.

Turns out this is disturbingly close to the truth:

Coltan is the colloquial African name for (columbite-tantalite), a metallic ore comprising niobium and tantalum.

[...]

Coltan smuggling has also been implicated as a major source of income for the military occupation of Congo. To many, this raises ethical questions akin to those of conflict diamonds. Owing to the difficulty of distinguishing legitimate from illegitimate mining operations, several electronics manufacturers have decided to forgo central African Coltan altogether, relying on other sources.


On the other hand, it looks like coltan is more important as a source of tantalum, and most niobium comes from Brazil and Canada. So probably our research isn't built on slave labor and exploitation (postdoc salaries aside).

Permalink | Tags: Lab, Physics, World

August 21, 2006

Dark Matter

Posted by Arcane Gazebo at 3:03 PM

Recently (I think during my Connecticut visit) I was talking to somebody about whether dark matter is real, or just a kind of fudge factor reflecting something we don't understand about gravity. It turns out there's recent evidence that strongly points to the former case—there really is a lot of weakly-interacting stuff out there that can't be explained by modifying general relativity. Sean Carroll explains at Cosmic Variance.

Permalink | Tags: Physics, Science

August 15, 2006

Measurements of gravity using cryogens [Updated]

Posted by Arcane Gazebo at 7:00 PM

This is what Chad Orzel refers to as a True Lab Story:

Condensed matter labs such as ours receive frequent deliveries of liquid nitrogen in one- or two-hundred liter dewars. Unfortunately, most of the Berkeley cond-mat labs are in Birge Hall, which has no loading dock, so that the LN2 dewars arrive on the first floor of neighboring LeConte where they must be wheeled over to their destination by some low-seniority student. Since the Berkeley campus is on a hill, the loading dock at the back of the building is one floor higher than the other entrances to LeConte and all the entrances to Birge. One can push the dewar around the outside of LeConte, but a shorter route is to take the elevator down one floor and go out the side door.

Yesterday the LeConte elevator was out of order, which for most of us would have meant taking the long way around. However, one undergrad, tasked with transporting a full 230L dewar, simply decided to take the stairs.

At about 80% the density of water, 230 liters of liquid nitrogen weighs about 400 pounds, not counting the additional weight of the steel vessel containing it. When rolled onto the stairs, the dewar promptly tipped over and plummeted downward on its side, knocking deep gouges in the marble steps and dragging along the unfortunate student, who inexplicably held on as his cargo began to tumble. Miraculously both student and dewar arrived at the landing without rupturing, but the dewar was still on its side and pressure was building up.

This was the situation when we got the frantic call from the building manager; once enough of us arrived at the scene we were able to pull the dewar upright and release the pressure. This averted any imminent explosion, but now we had a different problem: 400 pounds of liquid nitrogen stranded on a landing between the ground and first floors. Suggestions were floated including emptying the nitrogen out the nearby window, but ultimately we found another dewar which was wheeled to the top of the stairs on the first floor, and the nitrogen was transferred there through a long hose. The empty dewar was then carried up the stairs, a task requiring four men and gouging new (but shallower) grooves in the staircase.

Recalling what happens when a LN2 cylinder does rupture, it's the general consensus that this student is lucky to have survived and LeConte Hall is lucky to still have a staircase.

Photos below the fold [updated with photo of wall damage]:

Continue reading "Measurements of gravity using cryogens [Updated]"
Permalink | Tags: Lab, Photos, Physics, Science

August 3, 2006

Long-running experiments, or, sub-optimal thesis topics

Posted by Arcane Gazebo at 4:43 PM

I'm still catching up on my reading—this is from a Boing Boing post yesterday, so you may have seen it already. Anyway: three very long-running physics experiments. I had read about the pitch drop experiment before, but the others were new to me.

Unmentioned is the fact that the flood levels of the River Nile have been measured for thousands of years, providing the lowest-frequency data on 1/f noise in existence.

Permalink | Tags: Physics, Science

July 10, 2006

Singing Sand Solved

Posted by Arcane Gazebo at 3:58 PM

An interesting paper appeared in PRL a few days ago on the phenomenon of "singing sand" (I've also heard it called "booming sand"). Sand dunes in certain locales are known to produce sounds at particular frequencies, with the frequency apparently depending only on the size of the grains of sand. One can take a sample of sand out of the dunes (perhaps in Capt. Sparrow's jar of dirt) and reproduce the sound from it. This was a classic modeling problem in Caltech's Ph 11 class, but in this PRL the researchers actually did some experiments and found that the sand produces self-synchronized waves.

Song of the Dunes as a Self-Synchronized Instrument

S. Douady, A. Manning, P. Hersen, H. Elbelrhiti, S. Protière, A. Daerr, and B. Kabbachi

Since Marco Polo it has been known that some sand dunes have the peculiar ability to emit a loud sound with a well-defined frequency, sometimes for several minutes. The origin of this sustained sound has remained mysterious, partly because of its rarity in nature. It has been recognized that the sound is not due to the air flow around the dunes but to the motion of an avalanche, and not to an acoustic excitation of the grains but to their relative motion. By comparing singing dunes around the world and two controlled experiments, in the laboratory and the field, we prove that the frequency of the sound is the frequency of the relative motion of the sand grains. Sound is produced because moving grains synchronize their motions. The laboratory experiment shows that the dune is not needed for sound emission. A velocity threshold for sound emission is found in both experiments, and an interpretation is proposed.

Permalink | Tags: Physics, Science

June 20, 2006

Publication: Quantum theory of three-junction flux qubit with non-negligible loop inductance: Towards scalability

Posted by Arcane Gazebo at 11:37 AM

Here's the latest publication on Clarke group qubit research, which appeared in Physical Review B at the end of May. Normally I give a non-technical explanation in these posts, but this paper is entirely devoted to working out gory technical details. It essentially goes through how to calculate a priori the properties of the flux qubits that I've written about previously. This calculation had been done for "small" qubit loops—small being defined in terms of the loop inductance but corresponding to a few microns on a side—our qubits are much larger than this (100 microns) and so we needed to figure out the more general solution.

The vast majority of the work in this paper was done by T. L. Robertson; my primary contribution was checking the math and the Mathematica code.

Quantum theory of three-junction flux qubit with non-negligible loop inductance: Towards scalability

T. L. Robertson, B. L. T. Plourde, P. A. Reichardt, T. Hime, C.-E. Wu, and John Clarke
Phys. Rev. B 73, 174526 (2006)

The three-junction flux qubit (quantum bit) consists of three Josephson junctions connected in series on a superconducting loop. We present a numerical treatment of this device for the general case in which the ratio betaQ of the geometrical inductance of the loop to the kinetic inductance of the Josephson junctions is not necessarily negligible. Relatively large geometric inductances allow the flux through each qubit to be controlled independently with on-chip bias lines, an essential consideration for scalability. We derive the three-dimensional potential in terms of the macroscopic degrees of freedom, and include the possible effects of asymmetry among the junctions and of stray capacitance associated with them. To find solutions of the Hamiltonian, we use basis functions consisting of the product of two plane wave states and a harmonic oscillator eigenfunction to compute the energy levels and eigenfunctions of the qubit numerically. We present calculated energy levels for the relevant range of betaQ. As betaQ is increased beyond 0.5, the tunnel splitting between the ground and first excited states decreases rapidly, and the device becomes progressively less useful as a qubit.
Permalink | Tags: Physics, Publications, Quantum Information, Science

June 19, 2006

Quantum wiki

Posted by Arcane Gazebo at 5:44 PM

Via Mason, some guys at Caltech have set up a quantum information wiki intended for the research community. I added a page for myself, a stub page for the Clarke group, and updated their list of blogs to include this page and Mixed States. At the moment there's not much there from the solid state angle, so I may be back to contribute a bit more.

Permalink | Tags: Caltech, Internet, Physics, Quantum Information, Science

April 25, 2006

The physics of Built To Spill

Posted by Arcane Gazebo at 6:44 PM

And while I'm thinking about timescales, yesterday iTunes reminded me of the relevant Built To Spill song, "Randy Described Eternity". The song starts out like this:

Every thousand years
this metal sphere
ten times the size of Jupiter
floats just a few yards past the earth
You climb on your roof
and take a swipe at it
with a single feather
Hit it once every thousand years
`til you've worn it down
to the size of a pea
Yeah I'd say that's a long time
but it's only half a blink
in the place you're gonna be

It's a cool metaphor, but the physicist in me has a few questions for this Randy guy if I ever run into him:
  1. Wouldn't the gravity of the metal sphere crush the Earth into a thin paste? Or crush itself into a neutron star? Jupiter's diameter is 142,984 km, so the volume of the sphere in the song is about 1.5x1027 m3. Assuming the metal is iron near room temperature, and without accounting for gravitational compression, the mass of the sphere is 1.2x1031 kg, or 6 solar masses. I believe this is actually a little bit above the threshold to become not a neutron star but a black hole. On the other hand, maybe "size" means volume rather than radius, so that the mass is only 6% of a solar mass. In this case I don't think it turns into a neutron star, but gravity at the surface is still formidable. A quick calculation yields about 338 times Earth's gravity (at the surface of each object), unless I made a mistake.
  2. Even ignoring the gravitational binding, would a swipe from a feather be enough to knock a non-zero number of atoms off the sphere? Maybe I could model this but it seems slightly difficult. Someone should do an experiment with a feather, some iron, and an atomic force microscope (or similar instrument).
  3. Suppose the feather does knock some atoms off the sphere. Where do they go? If the metal sphere has gravity, of course they'll accrete right back onto the sphere. But if not, won't they pile up on the Earth? Given the size of the sphere that could be a problem. On the other hand, if there's magically no gravity from the sphere, maybe the individual atoms won't be affected by Earth's gravity either and they'll fly off into space.
  4. Won't the momentum imparted by the feather strikes affect the motion of the sphere over time, as well as the motion of the Earth? Will the thousand-year period change after enough swipes?

Clearly this song raises more questions than it answers. If I ever teach an elementary physics course, I should totally assign a problem based on these lyrics.

Permalink | Tags: Music, Physics, Science

Slow and fast timescales

Posted by Arcane Gazebo at 5:58 PM

Having just finished reading Spin (which I reviewed below) I found myself thinking about timescales. The novel did a good job of bringing long timescales into perspective, but what about short ones? In the book, the ratio between Earth time and solar time was about 108, one hundred million years outside the earth to each year in the Spin, or 3.17 years every second. This was an enormous ratio, with any timescale relevant to human civilization passing by in less than a day. It was mind-boggling to read about in the book. But I realized that I was sitting in the lab doing a diagnostic measurement in which I watched the response of a SQUID to an applied microwave field, and my software was acquiring about one point every second, at nanosecond resolution. That's a ratio of 109, ten times greater than the ratio in Spin. I usually don't think much about how long a nanosecond is, but it's really astonishingly short—as far removed from normal human timescales as stellar lifetimes.

It's not just in my lab—with gigahertz processors in wide usage, much of modern technology runs on nanosecond timescales. (And Windows still manages to be frustratingly slow at times, with billions of clock ticks in a second to work with.) Faster timescales are a bit harder to get to, at least in semiconductor electronics. The pulse generator I use in qubit experiments has a time resolution of 5 picoseconds, which always impresses me until I remember that the accuracy is only 250 ps. There's some research into a faster electronics technology using superconducting circuits and flux quantization, called Rapid Single Flux Quantum (RSFQ), which I believe gets to picosecond timescales. Berkeley professor emeritus Ted Van Duzer has been involved in this.

Anyway, I'm not sure I have much more insight into fast timescales than slow ones, but at least they're more accessible.

Permalink | Tags: Books, Life, Physics, Science

April 24, 2006

Serial psychoceramics

Posted by Arcane Gazebo at 4:06 PM

How not to earn credibility for your crackpot physics theories: spam them to physics graduate students, in paragraph-sized pieces sent every few hours, with subject lines like "Stephen Hawking died Today". And ask for monetary donations. For your amusement, here is the latest installment in the continuing series:

Subject: Stephen Hawking died Today (4-24-06)

The number two search Yahoo (4-24-06) result for "wave-particle duality" http://alpha.qmul.ac.uk/~zgap118/ states that:


"Light is a deformation of electric (E) and magnetic (B) fields in an area of space."

Maxwell states that light is not a substance but a process going on in an ether which forms an electromagnetic wave structure of light (Maxwell, vol 2, p. 765). Maxwell's ether does not exist in a vacuum yet light propagates in a vacuum which is proof that Maxwell's structure of light does not physically exist.

Maxwell's structure of light is represented with a continuous electromagnetic field structure where the planes perpendicular to the axis of propagation form a continuous electromagnetic field structure. A finite segment of the electromagnetic plane, of Maxwell's structure of light, forms an infinite number of positions. Each position, on the electromagnetic plane, forms an electric field; consequently, an infinite number of electric fields forms an infinite total energy. Maxwell's structure of light is not physically possible.

Maxwell, James. "The Scientific Papers of James Clerk Maxwell". Dover Pub. vol. 2. Edited by W.D. Niven. 1965.


I think at a minimum one should try to pass calculus before trying to overthrow Maxwell. I'd be eagerly awaiting the next episode (due sometime this evening) but I already instructed Thunderbird as to the appropriate destination of these messages.

Permalink | Tags: Physics, Psychoceramics, Science

April 10, 2006

Colloquium Blogging: Silly Edition

Posted by Arcane Gazebo at 6:05 PM

Today's colloquium was Steve Chu, Nobelist and director of Lawrence Berkeley Laboratory, giving an account of his biophysics experiments. However, rather than report on this I'm going to share a thought I had in the middle of the talk. At one point he was describing a standard optical tweezers technique in which ribosomes are engineered to stick to a tiny glass bead, which can then be manipulated with a laser beam. I was thinking there was something familiar about this, and I realized you could make a game out of it in which you have a biological sample with lots of components designed to stick to the bead, and then roll the bead around with the laser beam to pick them up... yes! Optical Trap Katamari Damacy!

On the other hand, I don't think the King of All Cosmos would be impressed by a 3 μm katamari.

Permalink | Tags: Colloquia, Games, Physics, Science

March 29, 2006

Wednesday Schrodinger's Cat Blogging: Coupled Qubits

Posted by Arcane Gazebo at 12:45 PM

The slides for my March Meeting talk, "Variable Coupling of Two Flux Qubits", are now available online. As promised, below the fold is a non-technical explanation of the results presented there. This work builds on the single-qubit work, about which I posted in August; it may be helpful to review that post before reading the following.

Continue reading "Wednesday Schrodinger's Cat Blogging: Coupled Qubits"
Permalink | Tags: Physics, Quantum Information, Science

March 27, 2006

Scary vs. gross [Open Thread]

Posted by Arcane Gazebo at 10:20 AM

It's spring break, but I don't have any vacation plans. I do have some travel lined up later on this spring: I bought my tickets for Coachella so I'll be seeing some of you there next month.

The Hills Have Eyes: This movie was so bad I'm just going to leave V for Vendetta on the sidebar. Normally I like horror flicks, but this one seemed unclear on the concept. Specifically, the film confuses "scary" with "gross", and so we get a lot of gore and ugly mutants but not a lot of suspense. Instead of being frightening the experience was merely unpleasant, and it wasn't even the most disgusting thing I'd seen all week (David Bowie's eyeball hanging out of its socket being the clear winner there). The protagonists are dumb even by horror movie standards—Roger Ebert writes pretty much his entire review on how dumb they are—and some of them are sufficiently annoying that I was rooting for the mutants within ten minutes or so. Some critics have suggested that the movie is an allegory for the Iraq war. Such a film would have been much more interesting; in reality the movie drags out a few political stereotypes but doesn't sign on to an agenda or pursue anything as sophisticated as an allegory.

Charles Stross:Iron Sunrise: Here's the problem with "hard sci-fi": sometimes the author knows just enough physics to get it wrong. For example: this novel's faster-than-light communication scheme involving EPR-style entangled qubits. Now, I'm one of the few readers of this book who actually has a pair of entangled1 qubits in his2 basement. But any competent physicist should know that information can't be transferred this way—you just get correlated random numbers. (You can make a one-time pad this way for quantum cryptography, and indeed this has been done.)

All this shows is that I'm a big nerd. Once I stopping thinking very hard about the physics in the book, it turned into a fun pulp novel, with spies, assassins, conspiracies, and Nazi villains (or near enough). Once the plot really got going I was hooked, and it was an excellent way to pass the time while I was stuck in the airport last weekend. One non-science complaint I had was that the plot twists were all telegraphed in advance, so there weren't any big surprises. However, the characters were well-written and just reading about their interactions was fun.

1It's actually debatable whether they are entangled (I suspect they are) but they are definitely coupled. More on this in an upcoming post.
2Actually, UC Berkeley's basement.

Arab Strap: The Last Romance: I felt like I am not nearly bitter enough to appreciate this album properly. And this is supposed to be one of Arab Strap's more uplifting records! Well, the tone does get happier as the CD plays, culminating in the nearly-triumphant "There Is No Ending". (The US version of the album has two bonus tracks, but that one is clearly the end of the album.) Overall this is a decent album with a few excellent tracks: the first song and the aforementioned last song; another one I like is "Don't Ask Me To Dance". For the most part I like the darker music, which probably means I should check out their other records which are supposed to be along the same lines. (This purchase finally prompted me to find out that the Belle & Sebastian album The Boy With The Arab Strap was named after this band, and not the other way around.)

Permalink | Tags: Books, Movies, Music, Open Thread, Physics, Quantum Information

March 24, 2006

Absurd claims

Posted by Arcane Gazebo at 3:57 PM

I'm going to steal yet another meme from Tyler Cowen, who asks: What is the most absurd claim you believe? "It should refer to a view which you actually hold, but many other smart people consider untenable and bizarre."

During a period overlapping heavily with my undergraduate years, my answer would have been that I think David Lewis' theory of possible worlds is largely correct; in particular the notion that all possible worlds are just as real as the actual world. I've only read excerpts from Lewis' works so I'm not prepared to accept or discredit his entire theory, but the underlying principle seemed right. Later, however, I realized that this could not possibly be true as I had imagined it: the reason being that the laws of physics in the actual world seem to be very regular and time-translation invariant, whereas there are many more grue-like worlds where the laws of physics randomly change than there are worlds like this one. So the probability of finding oneself in a world where the laws of physics are observably stable is vanishingly small. (A reasonable objection is that this probability isn't well-defined. But if all possible worlds are equally real I would be very surprised not to find myself in a world with some grue-ish properties.)

So I had to shelve this idea. I'm still don't have a convincing idea of what distinguishes the actual world from other possible ones, but I think there must be something, and maybe it has to do with why the laws of physics are fixed with time.

Anyway, I thought the modal realism thing would be an unusual answer to the question, but it was mentioned by the fourth commenter in the original MR thread so I guess not. But having given up on that some years ago, what is my current most absurd belief? Probably that many-worlds is the correct interpretation of quantum mechanics. (Even though I don't like to call it "many-worlds".) Of course this has some conceptual similarities with my previous absurd belief, but at least this one suffers from fewer grue-type problems.

Anyone else want to confess some absurd beliefs?

Permalink | Tags: Philosophy, Physics

March 22, 2006

Workplace Physics

Posted by Arcane Gazebo at 10:09 PM

Classical theory: I tend to occupy either my office on the first floor or the lab in the second basement. Obviously the office has the higher potential energy. By the work-energy theorem, I can be promoted to the higher-energy state by performing work on the system. Once I am up in the office, I write up the results of the experiment and the energy exits the system in the form of a publication, so I find myself back in the lab.

Quantum theory: My state oscillates between the lab and office levels. Timescales for transitions are on the order of several weeks. Spontaneous absorption of data will cause a transition to the office state; the office state will randomly decay into the lab state with emission of one quantum of data (a PRL submission). My state is entangled with the state of the dilution refrigerator: if I am observed in lab there is a very high probability that the fridge is running.

A thermodynamic digression: When I am away from my office for several weeks, the number of objects on my desk increases with time. When I am away from the lab for several weeks, the number of items in the lab decreases with time (roughly in proportion to their utility to other members of the group). Conclusion: the chemical potential in the lab is positive, while the chemical potential on my desk is negative.

Permalink | Tags: Lab, Life, Physics

March 20, 2006

Long Form [Open Thread]

Posted by Arcane Gazebo at 3:24 PM

My trip back from Baltimore took about 12 hours longer than it should have, but I eventually made it back. Despite attempts to catch up on sleep I still feel like I'm recovering—it was a busy week.

V for Vendetta: This is a powerful movie that mostly does a good job blending action/suspense with a political message. The setting is a near-future Britain which has slid into fascism after the deterioration of Iraq and some high-casualty terrorist attacks. (Meanwhile the United States has fallen into anarchy and civil war.) The plot centers around the masked-and-caped V, who pursues a personal vendetta against certain government officials, while working on a larger plot to overthrow the entire government in the spirit of Guy Fawkes. It wouldn't be correct to say that V is the hero of the movie—he's morally ambiguous at best and commits at least one act I found horrifying. However, the government he's fighting against is so much worse that he sometimes seems good by comparison.

The movie can be didactic at times, and the message is delivered in a heavy-handed way. However, I think the time for subtlety is past: the government we have right now is detaining citizens without trial, torturing innocent people, and asserting unlimited executive power. It's refreshing to see a movie that stands up and says straight out that we, as a citizenry, should not tolerate these things. I certainly don't think we need to blow up any buildings, and Guy Fawkes is the wrong model for this sort of thing, but the basic notion that the people have a right to replace an unacceptable government translates well to the ballot box.

As for the film qua action movie, it's generally well done. There is a thread of paranoid tension running throughout that works well to keep up the suspense—this is one of the ways that the politics reinforce the action. A sequence early-on in which V takes over the state-run television studio is especially good, and the climactic fight scene at the end is the sort of thing the Wachowskis excel at. There are a couple of points where the exposition/recapping becomes excessive and the suspense wanes, but it picks up again afterwards.

Anyway, I liked it. (Remember when I wrote short capsule reviews in the open threads?)

David Goodstein: Out of Gas: This book is Goodstein's effort to explain the interrelated problems of peak oil and climate change to a non-technical audience, and in doing so he explains the physics of energy and the historical development thereof. He sets forth a mostly pessimistic picture, anticipating oil supply problems in the very near future and associated social turmoil. Unfortunately I think he too quickly brushes off the economic arguments about alternative energies becoming more cost-effective as the costs of fossil fuels increase. I don't think this solves the problem but it should make the situation better than he expects. (One of the frustrating things about reading peak oil commentary is that physicists are frequently naive about economics, and economists naive about physics.) His treatment of the basic physics issues surrounding energy production is very good, however, and I would recommend it to a non-technical audience for that reason.

In the end, I am still not sure just how worried I should be about peak oil, but the answer is clearly non-zero.

Arctic Monkeys: Whatever People Say I Am, That's What I'm Not: This is the hot band over in Britain right now, and musical Anglophiles will find their sound pleasing. Imagine the drunken swagger of the Libertines with the guitar sound of Franz Ferdinand, and you have a good approximation. This CD hasn't quite achieved the heavy rotation of certain other recent British additions to my collection, but it's still pretty good. The major single seems to be "I Bet You Look Good On The Dancefloor" but several others are equally good, like "Fake Tales of San Francisco".

Permalink | Tags: Books, Caltech, Energy, Movies, Music, Open Thread, Physics, Science

March 14, 2006

Good day for a physics talk

Posted by Arcane Gazebo at 8:26 AM

Also, it's Albert Einstein's 127th birthday today. There's a lot of talk on Mixed States about "Pi Day" but this is contingent on the American convention for writing dates. Those countries that write the day first can instead celebrate "Pi Approximation Day" on July 22 (22/7).

Permalink | Tags: Physics, Randomness

March 6, 2006

Colloquium Blogging: Steve Koonin on the Energy Situation

Posted by Arcane Gazebo at 8:57 PM

Some of you know Steve Koonin from his days as Caltech's provost. He's now chief scientist at BP International, and gave the colloquium at Berkeley today under the title "A Physicist's View of the World's Energy Situation". The talk was extremely interesting and seemed like a very realistic assessment. Some of the points I took away (in a bit of random order):


The talk will eventually appear here as a webcast. I've been increasingly interested in energy issues lately and I found it to be a fascinating look at how the oil companies (or at least one of them) look at these things. Next week while I'm traveling I'll read Out of Gas and see what Koonin's fellow Caltech prof David Goodstein has to say about this. (Goodstein is clearly more pessimistic.)

Permalink | Tags: Colloquia, Energy, Physics, Science, Technology, The Future

February 27, 2006

A different take on quantum cuteness [Open Thread]

Posted by Arcane Gazebo at 3:32 PM

First, a follow-up link to the quantum interrogation post: Sean at Cosmic Variance explains the experiment in layman's terms. I'm guessing he wrote this post immediately after reading Cute Overload.

Anyway, it's now time to review the album I've been playing incessantly the last three weeks. No, not Loveless, the other one.

Belle & Sebastian: The Life Pursuit: I am hardly an unbiased source on this band, so when I say that the album is awesome you will probably not be surprised. At least I can say how it stands in relation to the other B&S records, which is what I spent the first ten or so plays trying to figure out. In general it has a somewhat different sound from their previous work. There's still the sunny mood that ran through most of Dear Catastrophe Waitress (in fact the word "sun" appears in two of the song titles), but without the orchestral feel that characterized the earlier LP's production. From a production perspective, it sounds fairly novel for this band. I'm not sure how I would descibe this new sound, but it's quite appealing and a good match for the themes of the album.

It feels very cohesive compared to Waitress (in which they seemed to be experimenting with various styles on the different tracks)—these songs flow into each other very smoothly, and when "Act of the Apostle II" picks up the theme from its predecessor halfway through, it feels completely natural despite the fact that the first "Act of the Apostle" played ten tracks earlier. This is not to say that there's no variety; "Dress Up In You", which sounds like an old-school B&S song, is sandwiched between "The Blues Are Still Blue" and "Sukie In The Graveyard", both of which are far peppier than is typical for this band.

On just about every Belle & Sebastian CD I've bought, there's been one song that I've fallen in love with and played to excess. Joining "Your Cover's Blown", "If She Wants Me", "String Bean Jean", and "Like Dylan in the Movies" is "The Blues Are Still Blue" from this record. I'm not sure what it is about this particular song (maybe the cowbell) but I can't get enough of it. Other highlights are "Funny Little Frog", "Another Sunny Day", and "Sukie in the Graveyard".

The iTunes version of this album offers two bonus tracks, neither of which is particularly essential. "Meat and Potatoes" sounds as if it was written for the Dr. Demento show, and "I Took A Long Hard Look" is forgettable. (Apparently these are also on the "Funny Little Frog" single.) Anyway, this only applies if you bought the CD but were considering getting the extra tracks; spend your $0.99 on "Your Cover's Blown" (from the Books EP) instead.

Permalink | Tags: Music, Open Thread, Physics, Quantum Information, Science

February 23, 2006

Counterfactual computation

Posted by Arcane Gazebo at 5:18 PM

I've been neglecting the blog the last few days, in favor of things like data analysis. Although I might have preferred to be doing things like Half-Life 2 instead, the data came out very well, and you will certainly see it if you attend my March Meeting talk.

In other quantum computing news, a group at UIUC has performed a very interesting experiment in which they combined quantum computing and quantum interrogation to get the result of a quantum algorithm without actually running it. (Via all over the place.) So at least one person will have a March Meeting talk that's much cooler than mine—for us "counterfactual computation" is when our qubits don't work—but in the spirit of quantum oneupsmanship I will note that my qubits are (allegedly) scalable.

UPDATE: John Holbo speculates about technological advances that may follow from this.

Permalink | Tags: Physics, Quantum Information, Science

February 19, 2006

Battle of the [Energy] Bands

Posted by Arcane Gazebo at 5:51 PM

Oops, I meant to blog this a little bit earlier, but fortunately it's not too late: Chad Orzel is polling on the Greatest Physics Experiment from a set of eleven nominees (which have been described in some detail in earlier posts at Uncertain Principles). So go over there and vote! My endorsement is for Cavendish. (Also, I regret not nominating Onnes for the discovery of superconductivity.) Preliminary results are here.

Permalink | Tags: Lists, Physics, Science

February 12, 2006

Climate Control

Posted by Arcane Gazebo at 3:41 PM

While the East Coast is buried in snow and Southern California struggles under a scorching heat wave, it's been 65 and sunny all week here in Berkeley. And we'll get the same weather in July. With this kind of climate, one might expect that the heating and air conditioning needs of a campus building like Birge Hall would be pretty minimal. And indeed, through efficient design the building is maintained at a pleasant environment with hardly any energy.

Ha! I'm joking, of course. What they actually do here is run the heating and the air conditioning at the same time so that they cancel out. I only discovered this fact this week, when the heat pump broke—leaving the air conditioning running unchecked. Naturally there's no way to adjust it, and so I end up carrying a sweater to lab with me, so that after walking through perfect weather to get there I can bundle up when I enter the building and avoid freezing to death.

Somehow, you'd think a physics building would have a more efficient solution to the problem of temperature control, but maybe it's a corollary to the fact that the architecture building is always the ugliest building on campus. It brings to mind a common method of temperature control in condensed matter physics: cool the sample down to 4.2K with liquid helium, and then use an electric heating element to warm it back up to the desired temperature. But I'm not sure it scales up as well as the designers of Birge Hall's HVAC system seem to believe.

Permalink | Tags: Berkeley, Lab, Life, Physics, UC Berkeley

January 21, 2006

Experimentalist bloggers and Joule heating

Posted by Arcane Gazebo at 10:50 PM

Yesterday Chad Orzel speculated about the relative absence of experimental physicists in the blogging community. Unfortunately, I didn't have time to comment until now, because I was busy working in the lab. (Actually we were gearing up for, and then undergoing, a major safety inspection. The inspectors, who were reminiscent of the consultants from Office Space, stood around trying to invent scenarios under which a graduate student could suffer oxygen deprivation folowing sudden helium vaporization in our dilution fridge.)

Anyway, Chad's hypothesis was that theorists spend more time in front of computers on a daily basis, and thus blogging is just more convenient. This seems right to me: I'm one of the few condensed matter experimentalists who maintains a blog (and it probably helps that I'm a grad student rather than a postdoc or on the tenure track), and whether or not I have time to post mostly depends on how much time I'm spending on the computer, versus in front of an oscilloscope or soldering iron (or bolting power strips to desks two feet above the floor to satisfy safety inspectors).

For a period of about 10 months last year, we did not have an experiment running as we were fabricating a new sample. And due to the division of labor among the grad students on this project, I was not closely involved with the fabrication process, and instead spent my time reading papers, writing papers and reports to funding agencies, writing software, designing circuits, and doing simulations. These were all computer-intensive activities, and I was able to get a fair amount of blogging done. For the last two months, however, we've been doing measurements on the chip we made last year, and I've spent a lot of time taking data, looking at scope traces, and reconfiguring wiring. Hence, I think up a bunch of posts over the week and write them up on Saturday night, which is a bit lame.

Fortunately, I do frequently have the ability to post even under these conditions, due to the phenomenon of Joule heating: if a current I is applied to an electrical resistance at a voltage V heat will be dissipated at a rate equal to the product IV. Every time we make a measurement, we apply a current pulse to our device, which produces a voltage and a corresponding amount of heat. If this heat is allowed to accumulate on the chip, it will wipe out the quantum effects we're trying to study, so between each measurement we have to wait long enough for the chip to cool off. In practice, this means instead of taking a million measurements in a second we are reduced to about 2,000. Furthermore, to get good statistics and sweep over an interesting range of parameters we have to take a large number of measurements, so it turns out that to get interesting results we need to measure continuously for at least 12 hours. I've written an overly baroque computer program to automate all this, so once I know what I want to measure, I can push a button to start the experiment, do something else for a while (usually analyzing data from the previous run), and then collect all the data hours later (or the next day). (This is only when everything is working properly; otherwise it's back to the oscilloscope and wiring diagrams.) And in the gaps I can do a little blogging.

These days, the trend in the superconducting qubit community is towards nondissipative readout—i.e., measurements which leave the device in the superconducting state and thus produce no heat. This might threaten to take away my blogging windows, except that it would also enable measurements that require even better statistics and broader sweeps, and so there will still be reasons to do 12- and 24-hour runs. (Actually, our record is about 48 hours, but we don't currently have the battery life to repeat that.)

Permalink | Tags: Lab, Life, Physics, Quantum Information, Science

2006 March Meeting Abstract

Posted by Arcane Gazebo at 6:42 PM

Less than two months remain before the APS March Meeting, which in terms of blogging means more short posts at odd hours, when I'm not in the lab trying to gather lots of last-minute data. Here's the abstract for my talk:

Abstract: K40.00012 : Variable Coupling of Two Flux Qubits
5:06 PM–5:18 PM

T. Hime, P.A. Reichardt, B.L.T. Plourde, T.L. Robertson, C.-E. Wu, A.V. Ustinov, John Clarke

We report observations of variable coupling of two flux qubits. The qubits are coupled inductively to each other and to a readout Superconducting QUantum Interference Device (SQUID). By applying microwave radiation to the device, we observed resonant absorption in each of the qubits when the level splitting in the qubit matched the energy of the microwave photons. Using the two on-chip flux bias lines we adjusted the bias of each qubit so that the energy levels of the two qubits were equal; we then observed a splitting of the resulting absorption peak characteristic of coupling between the qubits. We varied the coupling between the qubits by changing the current bias in the SQUID in the zero voltage state, thereby changing its dynamic inductance and thus modifying the effective mutual inductance between the qubits. We compare the resulting changes in splitting with our predictions. This controllable coupling should be extendable to many qubits.


I'll do a post explaining this in more detail around the time of my talk; some of this work is still, uh, "in progress". (In fact we have performed all the experiments mentioned in the abstract, but we are working on collecting more/better data.) The talk immediately before mine covers some other results from these experiments.

Permalink | Tags: Physics, Publications, Quantum Information, Science

December 25, 2005

363rd Newton's Birthday [Open Thread]

Posted by Arcane Gazebo at 10:34 AM

It's time once again for us to celebrate Newton's Birthday (which has a Wikipedia entry!). Some physics carols may be found here. Also check out that issue of Physics Today for physics songs. (Was it August '05? I don't have my collection here.)

Enjoy the holidays! Here's an open thread.

Permalink | Tags: History, Physics, Religion, Science

November 28, 2005

Colloquium Blogging: Recent Neutrino Findings

Posted by Arcane Gazebo at 10:21 PM

Today's colloquium was Stuart Freedman on the latest results from KamLAND, one of the neutrino detection experiments. The experiment is basically a gigantic vat of liquid scintillator—an oil convenient for producing photons from exotic particles passing through—surrounded by high-efficiency photon detectors. Neutrinos are produced in huge quantities by the sun and nuclear reactors, but they rarely interact with matter, so to observe them one needs to construct a very large detector and wait for a while.

I've always enjoyed following the neutrino experiments, since they came online about when I started to study physics, and since then they have made steady progress understanding this particle. It's a nice example of the incremental progress of science. Around my senior year in high school the story was "We've been assuming neutrinos are massless, but it's been suggested they do have mass and experiments are being constructed to look for it." (That was the year I went to IPhO, which was held in Sudbury, Canada, a town whose only distinction was that the Sudbury Neutrino Observatory was being built there, so we heard a lot on this subject.) Over the next few years the line became "Neutrinos might have mass," then "Neutrinos probably have mass (but we don't know what it is)". And in today's colloquium, the word was:

Freedman also spent some time on another angle of this experiment, in geophysics rather than fundamental physics. (I know I have some geophysicists reading, so you can correct me if I get this wrong.) There's a discrepancy between various estimates of the heat produced by the Earth, and one hypothesis (which is apparently not widely credited) is that the core of the Earth contains a natural nuclear reactor. Since KamLAND is built to detect neutrinos from man-made reactors, it could in principle look for one at the center of the planet as well. Except that KamLAND is (deliberately) built really close to a number of reactors in Japan, and any geophysical signal would be absolutely swamped by the signal from power plants. So in practice it looks like another detector would have to be built somewhere else to do this experiment.

Permalink | Tags: Colloquia, Physics, Science

November 27, 2005

"Mechanistic, Naturalistic and Evolutionistic Philosophy"

Posted by Arcane Gazebo at 10:01 PM

Via Katie in e-mail, the NYTimes has excerpts from textbooks for "Christian schools", published by (who else?) Bob Jones University.

And yes, there's a Physics for Christian Schools. It's disturbing that someone thought physics was too atheistic and needed to be all churched up. Physicists, on the other hand, are pretty godless compared to the general population. Anyway, here's an excerpt:

Some people have developed the idea that higher mathematics and science have little to do with the Bible or Christian life. They think that because physics deals with scientific facts, or because it is not pervaded with evolutionary ideas, there is no need to study it from a Christian perspective. This kind of thinking ignores a number of important facts to the Christian: First, all secular science is pervaded by mechanistic, naturalistic and evolutionistic philosophy. Learning that the laws of mechanics as they pertain to a baseball in flight are just the natural consequences of the way matter came together denies the wisdom and power of our Creator God. ... Second, physics as taught in the schools of the world contradicts the processes that shaped the world we see today. Trying to believe both secular physics and the Bible leaves you in a state of confusion that will weaken your faith in God's Word.

I have this perverse curiosity as to how exactly they remedy the mechanistic and naturalistic approach in "secular science" (a redundant phrase, I believe). Perhaps the equations are presented in the form "F = ma, because of Jesus."

Reminds me of the classic anti-evolution Chick tract in which it is asserted that the strong nuclear force is a falsehood, and that atomic nuclei are compelled to hold together by the power of Christ. And speaking of evolution, I can only imagine what their "biology for Christians" text is like. Good for the UC for not crediting some of these courses.

Permalink | Tags: Christianity, Physics, Religion

Useful Physics Aggregators

Posted by Arcane Gazebo at 4:34 PM

Those of you who come here for the physics blogging (which has been somewhat absent of late) may be interested in a couple of links I found recently, via referrals and Technorati:

Mixed States aggregates the RSS feeds of a number of physics blogs (including this one). Since the included bloggers are listed by their real name, it's a nice way to see who else in the community is blogging (although I didn't recognize any names that I knew from physics rather than from reading blogs).

Coherence * is a blog reviewing work in superconducting quantum computing, something that should be useful to me professionally (perhaps more so than the cond-mat RSS feed, which is high volume and a bit tough to sort by topic). Above their blogroll they list professors working in the field, including former Clarke group member and current collaborator Britton Plourde, but strangely not John Clarke himself. (However, there are at least four of John's former students/postdocs there, among other familiar names.)

Permalink | Tags: Internet, Physics, Quantum Information, Science

November 15, 2005

Stringing along

Posted by Arcane Gazebo at 1:18 PM

Yesterday's colloquium was entitled "String Theory and Cosmology", usually a sign that I can safely spend that hour in the lab trying to get my qubits to work. If I had known that the speaker would be giving the talk from handwritten transparencies I definitely would have stayed away, figuring that the talk was so overly technical that Powerpoint couldn't handle it, and the speaker would be running through some incomprensible morass of equations and text that had been lifted from the Necronomicon and then translated a couple times by Babelfish.

But fortunately I did go to the colloquium, which turned out to be pretty accessible. The speaker, Shamit Kachru, was very good and able to give sort of a hand-wavy outline of what string theorists are up to. String theory is a very difficult and jargon-heavy subject, and there was no way for him to get very technical without losing 95% of the audience (myself included), so I can't say that I gained much understanding of what string theories are actually about. However, I did at least grasp where the boundaries of knowledge are in this field, which I think can best be classified using the epistemological scheme invented by philosopher/poet Donald Rumsfeld:


Now, for serious string theory blogging you should be reading Cosmic Variance, since I don't really know much at all about the field beyond what can be communicated in an hour-long colloquium. However, I'm starting to understand why it's interesting. (Also, it turns out that the guys shambling down the halls around here muttering about "braaaaanes" aren't zombies but overworked string theorists. Oops.)

I just discovered that there are videos of the colloquia on the physics department website, here, so you can actually watch this talk if you're interested. (It hasn't been posted yet but probably will be within a week.) Another good one from this semester was "Cycles in Fossil Diversity" by Rich Muller, which was a study of what causes species to thrive or die out at apparently regular intervals in Earth's history.

Permalink | Tags: Colloquia, Physics, Science

November 14, 2005

Clarke group research in ScienceMatters@Berkeley

Posted by Arcane Gazebo at 6:25 PM

My advisor was profiled in the latest issue of ScienceMatters@Berkeley, an online UCB publication written by Boing Boing's David Pescovitz. Most of you know about my work on the qubit project; the ScienceMatters article also covers some of the other research in the group.

UPDATE: It's pretty cool to see one of our figures on Boing Boing, even if it is from the (admittedly more photogenic) MRI project rather than the qubit research.

Permalink | Tags: Lab, Physics, Publications, Science, UC Berkeley

November 8, 2005

Eminent physicist sentenced to prison

Posted by Arcane Gazebo at 5:57 PM

This is not the sort of story one expects to read about a physics Nobel laureate:

Nobel Prize-winning physicist gets 2 years in Santa Maria crash

Associated Press

SANTA MARIA, Calif. - A Nobel Prize-winning physicist was sentenced Monday to two years in prison for killing a man and injuring seven others when his speeding Mercedes-Benz slammed into a van.

John Robert Schrieffer, 74, a Florida State University professor who once taught at the University of California, Santa Barbara, pleaded no contest July 25 to felony vehicular manslaughter with gross negligence for crashing into the Toyota van near rural Orcutt.

Schrieffer had nine prior speeding tickets and was driving on a suspended license at the time of the Sept. 24, 2004 crash. He also admitted to a criminal enhancement of causing great bodily injury to three people in the van.


Schrieffer was the "S" in the BCS theory of superconductivity, which describes conventional superconductors and is therefore highly relevant to my own research. I've never seen him in person, but it's still kind of shocking. Later in the article his colleagues protest that he's not an "extreme personality", but nine speeding tickets? He sure sounds like a reckless driver, at least.

Via Fark, where the headline writer inexplicably went for quantum tunneling as the basis for the obligatory joke rather than something on resistanceless flow.

Permalink | Tags: California, Physics

October 24, 2005

Symmetries

Posted by Arcane Gazebo at 11:49 AM

Over at Cosmic Variance, Sean Carroll has a great post on spontaneous symmetry breaking. It's a nice treatment for those of us who never got around to taking a Standard Model course.

Carroll is actually in Berkeley today, giving the particle physics seminar, but the condensed matter seminar is at the same time so I won't be able to catch it. I probably wouldn't be able to follow his talk anyway, as it's a bit far afield for me.

Permalink | Tags: Physics, Science

October 13, 2005

Art/Physics collision

Posted by Arcane Gazebo at 2:49 PM

Via Boing Boing, some weirdly beautiful artistic renditions of elementary particles. I like the photon especially.

Can we get the artist to do some condensed matter stuff? I'd love to see Cooper pairs, quasiparticles, and phonons...

Permalink | Tags: Culture, Physics, Science

October 10, 2005

Nobels explained

Posted by Arcane Gazebo at 1:57 PM

Chad Orzel has posted his explanations of this year's physics Nobels: here's the post on Glauber and here's the one on Hall and Hänsch. I don't have much knowledge of quantum optics so this was pretty helpful.

Also, check out last week's open thread here for Jolene's explanation of the chemistry prize; she was a student of one of this year's laureates. I have no way to link to individual comments on my blog so you'll have to scroll past some scheduling chatter to find it.

The economics prize is covered at Marginal Revolution: Aumann is discussed here and Schelling here; Tyler Cowen was Schelling's student.

Permalink | Tags: Physics, Science

October 4, 2005

Frickin' Laser Beams

Posted by Arcane Gazebo at 3:43 PM

The physics Nobel was announced today:

Nobel given for laser measurement

Three scientists have been awarded the 2005 Nobel Prize for Physics for laser measurement and quantum optics.

Half of the prize went to John Hall of Colorado University and Theodor Hänsch of Germany's Max Planck Institute.

The laser-based spectroscopy they have pioneered allows the colour of light from atoms and molecules to be determined with exceptional precision.

The other half went to Roy Glauber of Harvard University for applying modern quantum physics to optics.


This is Chad Orzel's field, so I'll wait for him to post his explanation of their findings, and then link to it.

Permalink | Tags: Physics, Science

September 7, 2005

Dancing as an ensemble of spins in a magnetic field

Posted by Arcane Gazebo at 9:46 PM

At tonight's ballroom dance class, the instructor at one point explained that it's important to finish a particular turn at the appropriate angle, so that when the motion is reversed one ends up at the original angle. Of course, my brain immediately translated this into the all-too-familiar concept of phase coherence and the difficulties of random phase noise. Unfortunately the foot-change doesn't act as a spin-echo pulse to correct the phase variation.

My personal dephasing rate appears to be very high. And let's not even talk about my foot parity non-conservation.

Permalink | Tags: Life, Physics

September 6, 2005

Speaking on Theory, Theory on Speaking

Posted by Arcane Gazebo at 6:36 PM

You may be wondering where I disappeared to, perhaps imagining that I was pursuing adventure and excitement during the long weekend. This was true during the first half, but Sunday afternoon I had to face the fact that I had been assigned the first group seminar of the semester. (In fact, I was due to give a talk towards the end of last semester, but managed to put it off for about five consecutive weeks until I was saved by the end of the term. Unfortunately I was still at the front of the queue when we started up again.)

For a topic I chose to review an 18-page theory paper: partly because I had no better ideas, partly because I wanted to do something relatively impressive, and partly out of sheer masochism. I would have expected such a task to consume my entire weekend rather than just half of it (and much of today), but fortunately the paper was not as daunting as it looked. This was for several reasons:

  1. As theory papers go, this one was not very dense. There was lots of text to go with each equation, and they mostly explained the algebra involved.
  2. After establishing the major equations governing the problem, they confine their solution to a particularly easy special case.
  3. For this special case, they give a "formal solution": i.e., when they get to a difficult integral equation, they declare themselves done with the equivalent of "if we knew how to solve this, here's what it would look like".
  4. Having obtained the formal solution, they set their computers on the problem, leaving the second half of the paper primarily to an avalanche of plots illustrating the numerical results.

My strategy for assembling my talk was to start by putting the numerical plots on Powerpoint slides, so that if I ran out of preparation time I could do the rest of the talk on the whiteboard. It turned out I had time to put everything into Powerpoint, which was nice since my whiteboard handwriting isn't terribly legible. For a denser theory paper, I would certainly use the whiteboard since it's tough to get the pacing right for mathematical derivations in Powerpoint. Also it's annoying to construct equations on the computer; I try to copy them from the PDF of the original article when possible, but sometimes I have to fill in steps or rearrange something into a clearer form.

I've noticed lately that when I'm giving a talk or a speech I seem to go into a kind of trance where I construct and deliver sentences without thinking about them on a conscious level. (This is not normally the case unless I am sufficiently inebriated.) This is absolutely essential because I can shut down the conscious part of my mind and therefore not notice that lots of people are watching me. One might ask why I can't duplicate this in normal conversation, and the answer seems to be that I rely on the prompts from my prepared notes or slides or whatever, and in more free-form circumstances some more conscious thought is necessary. I used to have difficulties with freezing up during the question period following a talk and I think this is the reason. (I've since improved in this regard.)

Permalink | Tags: Academia, Life, Physics, Science

August 25, 2005

Coincidentally, I am eating their research subject as I post this.

Posted by Arcane Gazebo at 9:30 PM

In high school physics class we watched a video about Richard Feynman, and in one scene he talked about a problem that occurred to him while cooking dinner with a friend one evening. The problem: why do strands of dried spaghetti break into more than two pieces? He and his friend became utterly distracted from their dinner, instead spending the evening snapping spaghetti in half and trying to understand the process. They never solved the problem.

It was reported last week that the answer has been found. It turns out that the initial break in the spaghetti sends waves down the strand, and these waves increase the stress as they pass by, creating additional breaks.

Supposedly this is actually useful:

The team points out that the motivation for this research extends far beyond the kitchen. The brittle steel struts in skyscrapers, buildings and bridges can fragment by similar mechanisms, so this research can have practical implications in helping to make structures safer.

"The physical process of fragmentation is relevant to many areas of science and technology," they declare.


The experimenters' website is here (with video!). Their paper came out today in PRL; it can be found here.

Permalink | Tags: Physics

August 22, 2005

Follow-up on decoherence

Posted by Arcane Gazebo at 3:14 PM

One of the comments on the flux qubit post asked an important question: where does the decoherence come from? I dealt with this a bit in the thread itself, but this post will be a less technical treatment.

In general, decoherence is a result of the fact that the qubit under study isn't in isolation, but interacts with some larger environment. Through this interaction, information that starts out concentrated in the qubit dissipates out into the environment, and likewise information in the environment mixes into the qubit. Of course, the state of the environment isn't known beforehand so the information that mixes in just looks random, and averages out over a large number of experiments.

In the case of our qubit, what matters is the electromagnetic environment—the electric and magnetic fields that act on the qubit. Any fluctuations in these fields can produce decoherence, and just about everything produces some level of field noise.

Continue reading "Follow-up on decoherence"
Permalink | Tags: Lab, Physics, Quantum Information, Science

August 18, 2005

Publication: Flux qubits and readout device with two independent flux lines

Posted by Arcane Gazebo at 7:36 PM

This paper contains the major results of my graduate research so far, compressed into four pages. Instead of the abstract I'm posting something closer to a layman's explanation, which is below the fold since it got a bit long.

Flux qubits and readout device with two independent flux lines
B. L. T. Plourde, T. L. Robertson, P. A. Reichardt, T. Hime, S. Linzen, C.-E. Wu, and John Clarke
Phys. Rev. B 72, 060506(R) (2005)

Continue reading "Publication: Flux qubits and readout device with two independent flux lines"
Permalink | Tags: Lab, Physics, Publications, Quantum Information, Science