Category Archives: Science

March Meeting, Day 1

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.

The brilliant unintentional comedy of Conservapedia

I don’t normally go reading crackpot right-wing sites for my own amusement, but Conservapedia is one of the funniest things I’ve ever seen. In fact, I’d be certain it’s a parody if not for Andrew Schlafly’s presence as a major editor. As the name suggests, Conservapedia is supposed to be a “fair and balanced” (in the Fox News sense) alternative to Wikipedia, which apparently suffers from liberal bias. The editors of Conservapedia have helpfully (and hilariously) listed their grievances against Wikipedia, which include such major offenses as:

1. Wikipedia allows the use of B.C.E. instead of B.C. and C.E. instead of A.D. The dates are based on the birth of Jesus, so why pretend otherwise? Conservapedia is Christian-friendly and exposes the CE deception.

and

5. Wikipedia often uses foreign spelling of words, even though most English speaking users are American. Look up “Most Favored Nation” on Wikipedia and it automatically converts the spelling to the British spelling “Most Favoured Nation”, even there there are far more American than British users. Look up “Division of labor” on Wikipedia and it automatically converts to the British spelling “Division of labour,” then insists on the British spelling for “specialization” also.[3]. Enter “Hapsburg” (the European ruling family) and Wikipedia automatically changes the spelling to Habsburg, even though the American spelling has always been “Hapsburg”. Within entries British spellings appear in the silliest of places, even when the topic is American. Conservapedia favors American spellings of words.

Now, this project is still fairly new so one doesn’t expect to find extended entries on many topics. Nonetheless I was disappointed to find that many entries are… well, “half-assed” doesn’t quite describe it. It’s more like 1%-assed. A lot of entries consist of a single sentence lifted from an appropriately slanted textbook (sample title: Exploring Creation With Biology). (I want to mention that I hit the “random page” button once to find that example.) And a lot of the more likely fodder for entertainment (such as the entry for evolution) has already been edited by visiting liberals in an attempt to either correct or parody, either of which makes it less funny. Nevertheless, the best examples of teh crazy occur where you don’t expect: these guys object not just to evolution but to relativity, and there are some other gems as well. (I’m linking to people who have quoted them, since the original entries have probably changed by now.) I recommend just clicking random pages until you find something good.
Although the temptation to troll the site is immense, I have to agree with those who say we liberals should leave it alone and see what develops. The intra-wingnut edit wars alone should be worth it.

2007 March Meeting Abstract

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.

Publication: Solid-State Qubits with Current-Controlled Coupling

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.

NYT Magazine on science fraud

The New York Times Magazine has a piece about another instance of scientific fraud, this time by a clinical researcher:

Poehlman pleaded guilty to lying on a federal grant application and admitted to fabricating more than a decade’s worth of scientific data on obesity, menopause and aging, much of it while conducting clinical research as a tenured faculty member at the University of Vermont. He presented fraudulent data in lectures and in published papers, and he used this data to obtain millions of dollars in federal grants from the National Institutes of Health — a crime subject to as many as five years in federal prison. Poehlman’s admission of guilt came after more than five years during which he denied the charges against him, lied under oath and tried to discredit his accusers. By the time Poehlman came clean, his case had grown into one of the most expansive cases of scientific fraud in U.S. history.

I was initially surprised by this passage describing the alteration of data from one experiment:

The fall that DeNino returned to the lab, Poehlman was looking into how fat levels in the blood change with age. DeNino’s task was to compare the levels of lipids, or fats, in two sets of blood samples taken several years apart from a large group of patients. As the patients aged, Poehlman expected, the data would show an increase in low-density lipoprotein (LDL), which deposits cholesterol in arteries, and a decrease in high-density lipoprotein (HDL), which carries it to the liver, where it can be broken down. Poehlman’s hypothesis was not controversial; the idea that lipid levels worsen with age was supported by decades of circumstantial evidence. Poehlman expected to contribute to this body of work by demonstrating the change unequivocally in a clinical study of actual patients over time. But when DeNino ran his first analysis, the data did not support the premise.
When Poehlman saw the unexpected results, he took the electronic file home with him. The following week, Poehlman returned the database to DeNino, explained that he had corrected some mistaken entries and asked DeNino to re-run the statistical analysis. Now the trend was clear: HDL appeared to decrease markedly over time, while LDL increased, exactly as they had hypothesized.

From this it sounds like Poehlman took potentially interesting data that went against existing hypotheses, and changed it so that it lined up with the conventional wisdom in the field. In other words, he fabricated data to make his results less interesting. This is the opposite of how scientific fraud usually works—consider the Jan Hendrik Schön case in condensed matter physics, where Schön invented spectacular and unexpected results that other groups were unable to reproduce.
But reading further in the article, it makes sense: this is how Poehlman was able to present fraudulent data for so long without getting caught. His results seemed solid enough to be impressive, but not surprising enough to draw too much attention.

The length of time that Poehlman perpetrated his fraud — 10 years — and its scope make his case unique, even among the most egregious examples of scientific misconduct. Some scientists believe that his ability to beat the system for so long had as much to do with the research topics he chose as with his aggressive tactics. His work was prominent, but none of his studies broke new scientific ground. (This may also be why no other scientists working in the field have retracted papers as a result of Poehlman’s fraud.) By testing undisputed assumptions on popular topics, Poehlman attracted enough attention to maintain his status but not enough to invite suspicion. Moreover, replicating his longitudinal data would be expensive and difficult to do.

It’s a pretty sad story, and I wonder what medical discoveries might have already been made if this guy had not been obscuring these issues with fabricated data.

Berkeley Physicist wins Nobel

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.

Yet more on gender stereotypes

Language Log is continuing their series of posts on gender stereotypes; I found this one on personality differences interesting. They look at a Science paper which ranks groups of men, women, and individuals with autism or Asperger’s Syndrome in terms of an “empathizing quotient” and “systematizing quotient”. Men on average score as more systematizing and women as more empathizing but there’s a large overlap between the distributions:

Those are the SQ distributions but the EQ ones look similar from the scatter plot. It turns out that one can take this personality test online. I come up with SQ=69 and EQ=32; perhaps surprisingly I am within 1σ of the mean for the male population on both indices.
It’s not entirely clear what these numbers say about me, other than that I’m more likely than most to have an organized record collection (alphabetized by artist, and each artist’s records ordered by release date, in case you’re wondering).

LHC as a black hole generator

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.

Newsweek on the gender gap at Berkeley

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.