Author: dabacon

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Portrait of an Academic at a Midlife Crisis

Citations are the currency of academia. But the currency of your heart is another thing altogether. With apologies to my co-authors, here is a plot of my paper citations versus my own subjective rating of the paper. Hover over the circles to see the paper title, citations per year, and score. Click to see the actual paper. (I’ve only included papers that appear on the arxiv.)

If I were an economist I suppose at this point I would fit a sloping line through the data and claim victory. But being a lowly software developer, its more interesting to me to give a more anecdotal treatment of the data.

  • The paper that I love the most has, as of today, exactly zero citations! Why do I love that paper? Not because it’s practical (far from it.) Not because it proves things to an absolute T (just ask the beloved referees of that paper.) But I love it because it says there is the possibility that there exists a material that quantum computes in a most peculiar manner. In particular the paper argues that it is possible to have devices where: quantum information starts on one side of device, you turn on a field over the device, and “bam!” the quantum information is now on the other side of the material with a quantum circuit applied to it. How f’in cool is that! I think its just wonderful, and had I stuck around the hallowed halls, I probably would still be yelling about how cool it is, much to the dismay of my friends and colleagues (especially those for which the use of the word adiabatic causes their brain to go spazo!)
  • Three papers I was lucky enough to be involved in as a graduate student, wherein we showed how exchange interactions alone could quantum compute, have generated lots of citations. But the citations correlate poorly with my score. Why? Because it’s my score! Haha! In particular the paper I love the most out of this series is not the best written, most deep, practical, or highly cited. It’s the paper where we first showed that exchange alone was universal for quantum computing. The construction in the paper has large warts on it, but it was the paper where I think I first participated in a process where I felt like we knew something about the possibilities of building a quantum computer that others had not quite exactly thought of. And that feeling is wonderful and is why that paper has such a high subjective score.
  • It’s hard not to look this decades worth of theory papers and be dismayed about how far they are from real implementation. I think that is why I like Coherence-preserving quantum bit and Adiabatic Quantum Teleportation. Both of these are super simple and always felt like if I could just get an experimentalist drunk enough excited enough they might try implement that damn thing. The first shows a way to make a qubit that should be more robust to errors because its ground state is in an error detecting state. The second shows a way to get quantum information to move between three qubits using a simple adiabatic procedure related to quantum teleportation. I still hope someday to see these executed on a functioning quantum computer, and I wonder how I’d feel about them should that happen.
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When I Was Young, I Thought It Would Be Different….

When I was in graduate school (back before the earth cooled) I remember thinking the following thoughts:

  1. Quantum computing is a new field filled with two types of people: young people dumb enough to not know they weren’t supposed to be studying quantum computing, and old, tenured people who understood that tenure meant that they could work on what interested them, even when their colleagues thought they were crazy.
  2. Younger people are less likely to have overt biases against woman.  By this kind of bias I mean that like the math professor at Caltech who told one of my friends that woman were bad at spatial reasoning (a.k.a. Jerks).  Maybe these youngsters even had less hidden bias?
  3. Maybe, then, because the field was new, quantum computing would be a discipline in which the proportion of woman was higher than the typical rates of their parent disciplines, physics and in computer science?

In retrospect, like most of the things I have thought in my life, this line of reasoning was naive.
Reading Why Are There So Few Women In Science in the New York Times reminded me about these thoughts of my halcyon youth, and made me dig through the last few QIP conferences to get one snapshot (note that I just say one, internet comment troll) of the state of woman in the quantum computing (theory) world:

Year Speakers Woman Speakers Percent
2013 41 1 2.4
2012 43 2 4.7
2011 40 3 7.5
2010 39 4 10.2
2009 40 1 2.5

Personally, it’s hard to read these numbers and not feel a little disheartened.

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Why I Left Academia

TLDR: scroll here for the pretty interactive picture.
Over two years ago I abandoned my post at the University of Washington as a assistant research professor studying quantum computing and started a new career as a software developer for Google. Back when I was a denizen of the ivory tower I used to daydream that when I left academia I would write a long “Jerry Maguire”-esque piece about the sordid state of the academic world, of my lot in that world, and how unfair and f**ked up it all is. But maybe with less Tom Cruise. You know the text, the standard rebellious view of all young rebels stuck in the machine (without any mirror.) The song “Mad World” has a lyric that I always thought summed up what I thought it would feel like to leave and write such a blog post: “The dreams in which I’m dying are the best I’ve ever had.”
But I never wrote that post. Partially this was because every time I thought about it, the content of that post seemed so run-of-the-mill boring that I feared my friends who read it would never ever come visit me again after they read it. The story of why I left really is not that exciting. Partially because writing a post about why “you left” is about as “you”-centric as you can get, and yes I realize I have a problem with ego-centric ramblings. Partially because I have been busy learning a new career and writing a lot (omg a lot) of code. Partially also because the notion of “why” is one I—as a card carrying ex-Physicist—cherish and I knew that I could not possibly do justice to giving a decent “why” explanation.
Indeed: what would a “why” explanation for a life decision such as the one I faced look like? For many years when I would think about this I would simply think “well it’s complicated and how can I ever?” There are, of course, the many different components that you think about when considering such decisions. But then what do you do with them? Does it make sense to think about them as probabilities? “I chose to go to Caltech, 50 percent because I liked physics, and 50 percent because it produced a lot Nobel prize winners.” That does not seem very satisfying.
Maybe the way to do it is to phrase the decisions in terms of probabilities that I was assigning before making the decision. “The probability that I’ll be able to contribute something to physics will be 20 percent if I go to Caltech versus 10 percent if I go to MIT.” But despite what some economists would like to believe there ain’t no way I ever made most decisions via explicit calculation of my subjective odds. Thinking about decisions in terms of what an actor feels each decision would do to increase his/her chances of success feels better than just blindly associating probabilities to components in a decision, but it also seems like a lie, attributing math where something else is at play.
So what would a good description of the model be? After pondering this for a while I realized I was an idiot (for about the eighth time that day. It was a good day.) The best way to describe how my brain was working is, of course, nothing short than my brain itself. So here, for your amusement, is my brain (sorry, only tested using Chrome). Yes, it is interactive.

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A Paradox of Toom's Rule?

Science is slow.  You can do things like continue a conversation with yourself (and a few commenters) that started in 2005.  Which is what I’m now going to do 🙂  The below is probably a trivial observation for one of the cardinals, but I find it kind of interesting.
Let’s begin by recalling the setup.  Toom’s rule is a cellular automata rule for a two dimensional cellular automata on a square grid.  Put +1 and -1’s on the vertices of a square grid, and then use the following update rule at each step: “Update the value with the majority vote of your own state, the state of your neighbor to the north, and the state of your neighbor to the east.”  A few steps of the rule are shown here with +1 as white and -1 as blue:
Toom's RuleAs you can see Toom’s rule “shrinks” islands of “different” states (taking away such different cells from the north and east sides of such an island.)  It is this property which gives Toom’s rule some cool properties in the presence of noise.
So now consider Toom’s rule, but with noise.  Replace Toom’s update rule with the rule followed by, for each and every cell a noise process.  For example this noise could be to put the cell into state +1 with p percent probability and -1 with q percent probability.  Suppose now you are trying to store information in the cellular automata.  You start out at time zero, say, in the all +1 state.  Then let Toom’s rule with noise run.  If p=q and these values are below a threshold, then if you start in the +1 state you will remain in a state with majority +1 with a probability that goes to one exponentially as a function of the system size.  Similarly if you start in -1.  The cool thing about Toom’s rule is that this works not just for p=q, but also for some values of p not equal to q (See here for a picture of the phase diagram.)  That is there are two stable states in this model, even for biased noise.
Contrast Toom’s rule with a two dimensional Ising model which is in the process of equilibriating to temperature T.  If this model has no external field applied, then like Toom’s rule there is a phase where the mostly +1 and the mostly -1 states are stable and coexist.  These are from zero temperature (no dynamics) to a threshold temperature T, the critical temperature of the Ising model. But, unlike in Toom’s rule, if you now add an external field, which corresponds to a dynamics where there is now a greater probability of flipping the cell values to a particular value (p not equal to q above), then the Ising model no longer has two stable phases.
In fact there is a general argument that if you look at a phase diagram as a function of a bunch of parameters (say temperature and applied magnetic field strength in this case), then the places where two stable regimes can coexist has to be a surface with one less dimension than your parameter space.  This is known as Gibbs’ phase rule.  Toom’s rule violates this.  It’s an example of a nonequilibrium system.
So here is what is puzzling me.  Consider a three dimensional cubic lattice with +1,-1 spins on its vertices. Define an energy function that is a sum over terms that act on the spins on locations (i,j,k), (i+1,j,k), (i,j+1,k), (i,j,k+1) such that E = 0 if the spin at (i,j,k+1) is in the correct state for Toom’s rule applied to spins (i,j,k), (i+1,j,k), and (i,j+1,k) and is J otherwise.  In other words the terms enforce that the ground state locally obey’s Toom’s rule, if we imagine rolling out Toom’s rule into the time dimension (here the z direction). At zero temperature, the ground state of this system will be two-fold degenerate corresponding to the all +1 and all -1 state.  At finite temperature this model well behave as a symmetric noise Toom’s rule model (see here for why.)  So even at finite temperature this will preserve information, like the d>2 Ising model and Toom’s CA rule.
But since this behaves like Toom’s rule, it seems to me that if you add an external field, then this system is in a bit of paradox.  On the one hand, we know from Gibb’s phase rule, that this should not be able to exhibit two stable phases over a range of external fields.  On the other hand, this thing is just Toom’s rule, laid out spatially.  So it would seem that one could apply the arguments about why Toom’s rule is robust at finite field.  But these contradict each other.  So which is it?
 

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4 Pages

Walk up to a physicist at a party (we could add a conditional about the amount of beer consumed by the physicist at this point, but that would be redundant, it is a party after all), and say to him or her “4 pages.”  I’ll bet you that 99 percent of the time the physicist’s immediate response will be the three words “Physical Review Letters.”  PRL, a journal of the American Physical Society, is one of the top journals to publish in as a physicist, signaling to the mating masses whether you are OK and qualified to be hired as faculty at (insert your college name here).  I jest!  (As an aside, am I the only one who reads what APS stands for and wonders why I have to see the doctor to try out for high school tennis?)  In my past life, before I passed away as Pontiff, I was quite proud of the PRLs I’d been lucky enough to have helped with, including one that has some cool integrals, and another that welcomes my niece into the world.
Wait, wht?!?  Yes, in “Coherence-Preserving Quantum Bits” the acknowledgement include a reference to my brother’s newborn daughter.  Certainly I know of no other paper where such acknowledgements to a beloved family member is given.  The other interesting bit about that paper is that we (okay probably you can mostly blame me) originally entitled it “Supercoherent Quantum Bits.”  PRL, however, has a policy about new words coined by authors, and, while we almost made it to the end without the referee or editor noticing, they made us change the title because “Supercoherent Quantum Bits” would be a new word.  Who would have thought that being a PRL editor meant you had to be a defender of the lexicon?  (Good thing Ben didn’t include qubits in his title.)
Which brings me to the subject of this post.  This is a cool paper.  It shows that a very nice quantum error correcting code due to Bravyi and Haah admits a transversal (all at once now, comrades!) controlled-controlled-phase gate, and that this, combined with another transversal gate (everyone’s fav the Hadamard) and fault-tolerant quantum error correction is universal for quantum computation.  This shows a way to not have to use state distillation for quantum error correction to perform fault-tolerant quantum computing, which is exciting for those of us who hope to push the quantum computing threshold through the roof with resources available to even a third world quantum computing company.
What does this have to do with PRL?  Well this paper has four pages.  I don’t know if it is going to be submitted or has already been accepted at PRL, but it has that marker that sets off my PRL radar, bing bing bing!  And now here is an interesting thing I found in this paper.  The awesome amazing very cool code in this paper  is defined via its stabilizer

I I I I I I IXXXXXXXX; I I I I I I I ZZZZZZZZ,
I I IXXXXI I I IXXXX; I I I ZZZZ I I I I ZZZZ,
IXXI IXXI IXXI IXX; I ZZ I I ZZ I I ZZ I I ZZ,
XIXIXIXIXIXIXIX; Z I Z I Z I Z I Z I Z I Z I Z,

This takes up a whopping 4 lines of the article.  Whereas the disclaimer, in the acknowledgements reads

The U.S. Government is authorized to
reproduce and distribute reprints for Governmental pur-
poses notwithstanding any copyright annotation thereon.
Disclaimer: The views and conclusions contained herein
are those of the authors and should not be interpreted
as necessarily representing the official policies or endorse-
ments, either expressed or implied, of IARPA, DoI/NBC,
or the U.S. Government.

Now I’m not some come-of-age tea party enthusiast who yells at the government like a coyote howls at the moon (I went to Berkeley damnit, as did my parents before me.)  But really, have we come to a point where the god-damn disclaimer on an important paper is longer than the actual definition of the code that makes the paper so amazing?
Before I became a ghost pontiff, I had to raise money from many different three, four, and five letter agencies.  I’ve got nothing but respect for the people who worked the jobs that help supply funding for large research areas like quantum computing.  In fact I personally think we probably need even more people to execute on the civic duty of getting funding to the most interesting and most trans-form-ative long and short term research projects. But really?  A disclaimer longer than the code which the paper is about?  Disclaiming, what exactly?  Erghhh.

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The Quantum Interregnum Decoherence Continues

The College of Cardinals has been in conclave for over a month now and leaks to the public indicate that the cardinals are still stalemated.  What does this portend for the world?  The end?  A new beginning?  Only entropy (which others call time) will tell.

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Quantum Interregnum!


The Vicar of Randomization hereby informs the readers of this blog that the Quantum Pontiff Dave Bacon XLII has decohered.  He further informs the readers of this blog that the entire Quantum Pontiff blog is in Justitium and hopes that the readers will refrain from acting like Canucks fans after losing the Stanley Cup.
The College of Cardinals will begin conclave in the coming days, please stay tuned to this chimney.

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Goodnight CSE

good night room

goodnight nom de plume

goodnight notebooks

goodnight tests

goodnight grants

goodnight Mike and goodnight Ike

goodnight publish

and goodnight perish

goodnight whiteboard

goodnight star, goodnight air
goodnight noises everywhere.

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Oh the Places I've Been!

In 1996 I participated in Caltech‘s Summer Undergraduate Research Fellowship program under the direction of two postdocs, Nicolas Cerf and Chris Adami (their big boss now works the halls of D.C.) The research project I worked on was to try to see whether quantum computers could efficiently solve NP-complete problems. Or as I like to say, my SURF was spent bashing my head up against the wall (and getting damn good at tensor products and spotting non-linear transforms, as you can see from my SURF writeup. John Preskill told me after my talk, in the first words he ever uttered in my direction: “that was a hard problem you worked on.”)
My SURF project was not my first introduction to quantum computing, but it was the first time I’d gotten a chance to bash my head up against the field, and something must have stuck. Because when I went to grad school in Berkeley in 1997, after a year of taking astrophysics courses (if the cosmic microwave background was distributed this way or that way on the sky, this or that cosmological model could be ruled out, how cool is that!) I stumbled back into quantum computing through the group of Chemistry Professor K. Birgitta Whaley and her postdoc Daniel Lidar. My first paper in quantum computing was published in 1999, and I’ve been a proud participant in the growing field of quantum information science ever sense.
Now that I’ve decided that it is time for a change and I’m moving out of the ivory tower and into the real world (academics, you see, manufacture their own reality, which is why they call everything outside of academia “the real world”), I thought it would be fun to indulge in a little bit of egotistical self-reflection, cataloging the joys that a decade plus spent in quantum computing has given me.  The joys of all of the papers I’ve written and all of the cool quantum computing stuff I’ve see?  No, that would be too easy.  Instead I thought it would be fund to think about the kind of crazy things that happen to you as life sweeps you along.  Or, as I like to say it, “Oh the places I’ve been!”
[Warning: self-flattering ego-inflating stories ahead!]
Things I’ve gotten to do that were pretty damn awesome:

  • I lectured a rich guy who’d just sold his company for many millions of dollars about quantum computing while standing on the walkway surrounding the 200-inch Hale telescope.  This will definitely be the only time I’ve been driven to give a scientific talk in a limo!
  • Parked my Mazda Miata with QUBITS license plate beside Murray Gell-Mann’s Range Rover sporting the license plate QUARKS while at the Santa Fe Institue.  One day I missed a major missed opportunity because of this.  Ben Schumacher was visiting the Santa Fe Institute… so I had the chance to get a picture of two people who have invented words that start with “Q”, that are in the dictionary, in front of two cars with license plates with those words!  I shall never forgive myself for this missed opportunity.


  • Played Isaac Newton to Scott Aaronson’s Gottfried Leibniz.  Personally I think I got to play the more awesome scientist and damn if that Leibniz didn’t steal calculus from me.

  • Gave a lecture at a summer school in Brisbane, Australia where I discussed a stabilizer code which contained the operators XXXX and ZZZZ. XXXX is the name of a beer in Australia, so I knew this would be awesome for jokes about beer and sleep. Unfortunately I didn’t notice that I had named the stabilizer group that these two operators generated Sex. The subsequent accident jokes had a few people rolling in the aisles.

  • Participated in a joint US/Australia NSF workshop in which I got to see Andrew White grill Australia’s Minister for Industry, Science and Resources(?) about education policy. During that trip I also got my finger stuck in an eye bolt when we were out on a cruise of Sydney Harbor, and had to get unstuck with the help of a stick of butter and an NSF program manager.  Oh, and I also got kicked into a nightclub on that trip.
  • Quantum Beer Night in Berkeley (at the Albatross) became Quantum Margarita Night at Caltech, where it made the list of top geek hangouts in Popular Science!
  • I got to hear Cormac McCarthy tell stories during SFI tea time, and found out that he deeply understands Bell inequalities.  Also at SFI I tied myself up to the corners of the lecture hall during a talk to demonstrate how SU(2) is related to the real world.
  • Got sick of looking at the arXiv every morning and so crowdsourced the daily task of filtering these posts by creating the website scirate.com.  Thank you people for doing so much filtering for me, you really have saved me a lot of time.
  • Gave a talk at Bungie about quantum video games.
  • Gave a talk in which I tried to sound like Martin Luther King Jr (BOMB)
  • Gave a talk that involved the use of subwoofers and speakers (sadly the file for this got corrupted and I no longer have the talk.)
  • Kept students amused during their exams by drawing cartoons:

  • Bought an iPhone and realized that it was a pain to surf for papers on the arXiv, so wrote an iPhone app for browsing the arXiv, arXiview.
  • Got a comment on my blog from a Nobel prize winner in physics.
  • Was once the top hit for the word “pontiff” on google. Take that Beattles!
  • Had a word stolen from me by Stephen Colbert: “Jesi.” Okay, well maybe not, but the ensuing discussion of the proper plural of Jesus is amusing.


Ah the things I’ve got to do.  So far.  Kind of makes me look forward to what kind of craziness is going to happen next 🙂