Conference Blogging: DAMOP Day 1

With attendees still trickling in after Tuesday's storms upset pretty much every mode of travel in Alberta, the DAMOP meeting opened with the Plenary Prize Session, and the first two talks were probably the highlight of the day, as far as I was concerned. Jun Ye and Jim Bergquist both work in precision measurement, and do some astonishing things.

Jun Ye talked about experiments with ultra-stable lasers, including so-called "frequency combs" which are lasers with a huge range of evenly spaced modes. The frequencies of these modes are all multiples of a single frequency, so they can be used to compare lasers from two very different regions of the electromagnetic spectrum, and those measurements can be absurdly precise. He talked about one measurement where they compared the frequency of two lasers separated by hundreds of nanometers in wavelength, and measured the difference between them with a resolution of less that one hertz (out of roughly 1,000,000,000,000,000 Hz).

Jim Bergquist is another ultra-precise laser guy, and he talked about optical frequency standards, in which transitions in the visible or ultraviolet regions of the spectrum are used to measure time. He also mentioned a frequency comb experiment, in which they compared a clock made using strontium to one using mercury, and measured the ratio between the frequencies to within a hertz or so. And only after a question did he note that the three measurements they've made also constitute a pretty competitive measurement of the time variation of the fine structure constant.

This is the sort of thing you have to be a big old geek to really appreciate. I don't have the temperment to do these sorts of experiments, but it makes me really happy to know that I share a field with people who very casually throw around the idea of measurments at the level of a few parts in 1018.

The other two talks I want to mention both came from Penn State:

Dave Weiss gave a nice invited talk about one-dimensional Bose gases. He's been working on this for a few years now, and I still don't entirely understand the physics behind it, but it's really elegant work, and gets at some pretty cool stuff.

The other talk from the Weiss group was given by a very nervous graduate student, and was probably slightly under-sold. The experiment involved directly imaging single atoms in an optical lattice. Basically, they load a bunch of cold atoms into a three-dimensional array of little traps, and after a short time, collisions between atoms knock out all the atoms that can be paired up within the wells, leaving only a series of single atoms randomly distributed around the wells f the lattice. Then they directly image these atoms using a high numerical aperture lens to collect the light scattered from individual atoms as they laser cool the sample.

Again, this is a big old geek sort of experiment, but I think it's really cool. When I was a grad student, we worked really hard to extract a measurement of the rate at which atoms hop from one site of an optical lattice to another from some collision data that we got. These guys measure the hopping rate by watching the atoms move. How cool is that?


More like this

My colleague, a cooler/trapper is gona try and watch the atoms back at our little place. He wants to look at non-Brownian motion, like Levy flights and such.

I remember one year at CLEO, one of the big things was watching quantum jumps, by watching fluorescence turn on and off via a 3 level shelving transition. The next year, I think it was Walther's group showed movies of ions forming quasi crystalline structures in traps, and someone asked why some would blink, and the answer was "oh thats just quantum jumps......"

Every year you DAMOP blog, and every year I think you have precision measurement envy.

Nice. I had Dave Weiss as a professor in a couple of classes when I was an undergrad at Berkeley (where he was before Penn State). Good to hear that he's kicking ass at PSU.

I'm glad to see you give metrology its due. You know, every intro textbook starts with a chapter on measurement, but the fact that physics is about measurement gets lost in all of the necessary theory and the crude approach to laboratory skills by first-year students.

The reason the meter went from a physical object to a wavelength to a time measurement is due to the precision you describe here. I am astounded that the precision for time measurement has gone from 10^{14} to 10^{18} in just a few decades. That is really impressive work.

By CCPhysicist (not verified) on 07 Jun 2007 #permalink