Category Archives: Theoretical highlights

Highlighting theoretical progress at IQIM.

Fundamental Physics Prize Prediction: Polyakov

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Rushing to produce a congratulatory post for Stephen Hawking yesterday, I didn’t mention the other big news regarding the Fundamental Physics Prize. Joe Polchinski, Sasha Polyakov, Charlie Kane, Laurens Molenkamp, and Shoucheng Zhang have received the 2013 Physics Frontiers Prize, making them eligible for the Fundamental Physics Prize to be announced on March 20. The New Horizon in Physics Prize (for young physicists) has been awarded to Niklas Beisert, Davide Gaiotto, and Zohar Komargodski. And another “special” $3M Prize, shared by seven people, appropriately recognizes the discovery of the Higgs boson.

The selection committee did a good job.

Joe Polchinski

Joe Polchinski

Joe Polchinski was a Caltech undergrad, class of 1975 (before my time here). I first met Joe in 1982 when he arrived as a postdoc at Harvard, where I was then on the faculty, and it did not take long for me to recognize his genius. I was teaching a course that fall on advanced quantum field theory, and Joe sat in, at least for a while. One of my lectures was about renormalizability, and I talked about how the renormalization group can organize and simplify the horrible combinatoric task of taming the overlapping divergences in Feynman diagrams to all orders of perturbation theory. I had learned this idea from Curt Callan‘s wonderful 1975 Les Houches Summer School Lectures.
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Stephen Hawking wins $3M Milner Prize

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The official announcement won’t come until tomorrow, but The New York Times is reporting that Stephen Hawking will receive a “special” $3M Prize from Yuri Milner’s Fundamental Physics Prize Foundation.

This is fantastic news! I assume the Prize recognizes Stephen’s great discovery that black holes radiate, one of the most transformative developments in theoretical physics during my lifetime. That’s just one of Stephen’s many important contributions. And of course his supreme skill as a popularizer and the unparalleled courage he displays in response to his disability have made him the most famous living scientist in the world. Congratulations, Stephen!

Stephen has a long-standing relationship with Caltech. He spent a sabbatical year here during 1974-75, when he wrote his famous paper formulating the black hole information paradox, and he has made more or less annual extended visits to Caltech since the 1990s. Stephen and I had many memorable discussions about black holes over the years, culminating when he conceded a bet, for which I received far more attention than I deserved. I’ve been proud to be Stephen’s friend for the past 30 years, and we’ve shared a lot of laughter.

With Kip Thorne and Stephen Hawking, 2005.

With Kip Thorne and Stephen Hawking, 2005.


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Is Alice burning? The black hole firewall controversy

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Quantum correlations are monogamous. Bob can be highly entangled with Alice or with Carrie, but not both.

Quantum correlations are monogamous. Bob can be highly entangled with Alice or with Carrie, but not both.

Back in the early 1990s, I was very interested in the quantum physics of black holes and devoted much of my research effort to thinking about how black holes process quantum information. That effort may have prepared me to appreciate Peter Shor’s spectacular breakthrough — the discovery of a quantum algorithm for factoring intergers efficiently. I told the story here of how I secretly struggled to understand Shor’s algorithm while attending a workshop on black holes in 1994.

Since the mid-1990s, quantum information has been the main focus of my research. I hope that some of the work I’ve done can help to hasten the onset of a new era in which quantum computers are used routinely to perform super-classical tasks. But I have always had another motivation for working on quantum information science — a conviction that insights gained by thinking about quantum computation can illuminate deep issues in other areas of physics, especially quantum condensed matter and quantum gravity. In recent years quantum information concepts have begun penetrating into other fields, and I expect that trend to continue.
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Quantum = Pink

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Need we say more?

What color do you imagine when you close your eyes and think “Quantum”? If you are to buy a case for your quantum computer, have you already picked your favorite color? (Okay, maybe it’s too early for that.)
Below I argue that the collective unconscious has already made the choice for you: it is going to be pink.

Excited?

Fear not. We will easily differentiate ourselves from warm and fluffy pink slippers. Our color is pink on black. Closer to purple, actually. We have good heritage: purple with white was the color of kings. But kings are no more, so let’s admit it: People think that “spooky” quantum phenomena have a purple glow around them. The disaster movie “Quantum Apocalypse” has a mysterious purple vortex approach Earth. Sci-fi now has “quantum cannons” shooting pink aura at the enemies, unleashing the chaos of uncertainty. You can’t fly your battlecruiser if you’re no longer certain you still have a battlecruiser.
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How to build a teleportation machine: Teleportation protocol

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Damn, it sure takes a long time for light to travel to the Pegasus galaxy. If only quantum teleportation enabled FTL Stargates…

I was hoping to post this earlier, but a heavy dose of writer’s block set in (I met a girl, and no, this blog didn’t help — but she is a physicist!) I also got lost in the rabbit hole that is quantum teleportation. My initial intention with this series of posts was simply to clarify common misconceptions and to introduce basic concepts in quantum information. However, while doing so, I started a whirlwind tour of deep questions in physics which become unavoidable as you think harder and deeper about quantum teleportation. I’ve only just begun this journey, but using quantum teleportation as a springboard has already led me to contemplate crazy things such as time-travel via coupling postselection with quantum teleportation and the subtleties of entanglement. In other words, quantum teleportation may not be the instantaneous Stargate style teleportation you had in mind, but it’s incredibly powerful in its own right. Personally, I think we’ve barely begun to understand the full extent of its ramifications.

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How to build a teleportation machine: Intro to entanglement

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Oh my, I ate the whole thing again. Are physicists eligible for Ben and Jerry’s sponsorships?

I’m not sure what covers more ground when I go for a long run — my physical body or my metaphorical mind? Chew on that one, zen scholar! Anyways, I basically wrote the following post during my most recent run, and I also worked up an agressive appetite for Ben and Jerry’s ice cream. I’m going to reward myself after writing this post by devouring a pint of “half-baked” brown-kie ice cream (you can’t find this stuff in your local store.)

The goal of this series of blog posts is to explain quantum teleportation and how Caltech built a machine to do this. The tricky aspect is that there are two foundational elements of quantum information that need to be explained first — they’re both phenomenally interesting in their own right, but substantially subtler than a teleportation device, so the goal with this series is to explain qubits and entanglement at a level which will allow you to appreciate what our teleportation machine does (and after explaining quantum teleportation, hopefully some of you will be motivated to dive deeper into the subtleties of quantum information.) This post will explain entanglement.
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Alesha

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An excerpt from my notes (including a misspelling of “repetition”) taken at Alexei Kitaev’s seminar during his first visit to Caltech in 1997. That was a very exciting day.

In 1997, I had some disposable funding as part of a quantum computing project, and decided to seize the opportunity to bring an interesting visitor to Caltech. But whom to invite? Chris Fuchs, then a postdoc at Caltech who seemed to know everybody working on quantum computing, reported that Richard Jozsa, while attending a conference in Japan, had met a remarkable Russian from the Landau Institute named Alexei Kitaev.
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An intellectual tornado

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Hello?… The first thing I remember feeling moments later was panic.

Five years before that day, I was a graduating senior at MIT pursuing a Bachelor of Science in Mathematics with Computer Science (18C for all the fellow nerds out there). I had been close to some of the most brilliant people I have ever met, like my undergraduate adviser Michael Sipser and my undergraduate research mentor in bioinformatics, Bonnie Berger. I had applied to several graduate schools to study mathematics, but had been summarily rejected by most of them. It was a humbling experience, which ultimately led me to the day I got the call. I remember clearly what day it was: February 6th, 2008. I was eating breakfast with two friends at a local diner in Davis, CA. Yes, the one place which had enthusiastically accepted me to their Ph.D. program was the Mathematics Department at UC Davis. In fact, being an international student from Greece, and given the tight State budget of California at the time (all the time), it was a miracle that UC Davis said yes. True, I had a good GPA and lots of research experience at MIT, but I did not have any direction. I did not apply to work with any particular Professor, I just applied by school name and reputation. And if it weren’t for Prof. Berger’s suggestion to apply to UC Davis, I would have applied to the top 5 graduate schools in Applied Mathematics and would be trading stocks in New York right now. I was naive.
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More to come

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John Wheeler. Photo by the New York Times/Redux.

As a sophomore at Princeton I took a class called Honors Physics from a man named Johnny Wheeler. He wore a suit and tie to class, loved explosions, and created vivid art in real time with colored chalk. Implausibly old, he had worked on nuclear fission with Niels Bohr. He was 61.

The lectures were long on inspiration and short on information about how to do the homework. I was in awe of Wheeler. Some students thought he sucked.

One day I arrived late to find Wheeler conducting a poll. We were voting on the future of science: is there “more to come” or “less to come”? I don’t remember the count, but “more to come” won handily. Wheeler was pleased.

Later, at a student-faculty lunch, Wheeler seemed troubled. He had been asked to explain the essence of quantum mechanics in five words or less, and was stumped. Frank Calaprice, a nuclear physicist within earshot, interjected helpfully, “What we expect to measure?” I was silent.

The question was absurd. It was fascinating. I still think about it. I can’t answer it.

This year I taught a course on quantum statistical physics to Caltech sophomores. I wore khakis and always used the white chalk. Though I’m 59, few students seemed awed. Some thought I sucked. Maybe I did sometimes.

Johnny Wheeler never blogged. If he had, some readers would have been awed. Some would have thought he sucked.

But Johnny would not have reminisced about a class he took 40 years ago. He knew there was more to come.

Welcome to Quantum Frontiers! We hope that the posts to come will be long on inspiration, even if short on information about how to do your homework. Enjoy!