Nordita Workshop for Science Writers, aka “Quantum Boot Camp”

Since this part of the trip is actually work-like, I might as well dust off the blog and post some actual physics content. Not coincidentally, this also provides a way to put off fretting about my talk tomorrow…

I’m at the Nordita Workshop for Science Writers on quantum theory, which a couple of the attending writers have referred to online as boot camp, though in an affectionate way. The idea is to provide a short crash course on cool quantum physics, so as to give writers a bit more background in subjects they might need to cover.

The first talk was from Rainer Kaltenbaek (whose name I was persistently misspelling on Twitter…), from Markus Apselmeyer’s group in Vienna. He gave an introduction to the ideas of entanglement and Bell’s theorem, then talked about efforts underway in Austria and elsewhere to try to do quantum interference of macroscopic objects. Their idea is to use nanoscale glass beads held in optical traps and cooled to extremely low temperatures, then released in a way that should produce a wave-like interference pattern. Unfortunately, to see the effect they want, they’d need to allow the waves to expand for something like 100 seconds, which would correspond to a free-fall drop of a bit less than 50km. Kaltenbaek dryly noted that “This isn’t something you want to try on Earth,” so they’re proposing to do it in space. You can find a couple of versions of their proposal on the arxiv.

I love this sort of stuff– it’s close enough to my own area that I can follow the details with relative ease, and the ambition is really impressive. They want to do this experiment with nanospheres on a satellite at one of the Lagrange points, so keeping the weight down is important. So rather than launching heavy vacuum pumps and cryogenic coolers, they’re just planning to mount the whole thing on the outside of the spacecraft. Which is an idea firmly in the “so crazy it just might work” category.

After lunch, we had a talk from Silke Weinfurtner on ways to simulate gravitational effects in systems that are a little easier to control, like flowing water. It turns out that a number of situations in hydrodynamics are described by equations that are nearly identical to those that show up in interesting problems in general relativity, like black and white holes. She also talked about how to simulate an expanding universe in a Bose-Einstein Condensate by changing the speed of sound, which is a very cool idea. This paper by Chris Westbrook’s group in Paris is related, and a terrific experiment to boot.

One of the coolest bits for me was a discussion of how to understand Hawking radiation as a scattering process, which relies on a model very much like one we used in one of my Ph.D. thesis papers (here’s a “making of” post as well). There’s a key mathematical difference in the particular function they’re using that means they get amplification of incoming fluctuations, which we don’t see in atoms, but the basic concept was very similar, and that was kind of mind-blowing.

The last talks of the day were from Marie Ericsson giving a survey of quantum computing. This one got a little hung up on the definitions of complexity classes (oh, what we wouldn’t have given for a computer scientist…), and then how to understand a Mach-Zehnder interferometer. This last ended up with me drawing pictures on the whiteboard, which I hope was sort of helpful. There was also some discussion of how Shor’s algorithm works, including multiple references to Scott Aaronson’s excellent explanation, which you should’ve read by now. I mean, it was posted in 2007…

Today’s program is lighter on talks– Ray Laflamme is talking about quantum information, then there’s a lab tour and general discussion. I’m talking on Friday. And with that, I probably ought to go review my slides…