Experiment
drorzel | August 1, 2013The last post in this series on the core technologies of cold-atom physics dealt with optical molasses, where you use the scattering of light to exert forces on atoms to make them very, very cold. It turns out, they end up even colder than the simple theory would lead you to expect, which is very surprising, but also essential to the revolutionary impact of cold atom physics. If you were stuck with the Doppler cooling limit temperatures, laser cooling probably wouldn't be as big a deal as it is now.
You can do better, though, thanks to the interaction of several bits of physics that go beyond…
drorzel | July 31, 2013`Once upon a time there were three little sisters,' the Dormouse began in a great hurry; `and their names were Elsie, Lacie, and Tillie; and they lived at the bottom of a well--'
`What did they live on?' said Alice, who always took a great interest in questions of eating and drinking.
`They lived on treacle,' said the Dormouse, after thinking a minute or two.
`They couldn't have done that, you know,' Alice gently remarked; `they'd have been ill.'
`So they were,' said the Dormouse; `VERY ill.'
-- Lewis Carroll, Alice's Adventures in Wonderland, Chapter 7
As an undergrad, I did my senior…
drorzel | July 30, 2013This series of posts is intended to explain the tools and tricks used to create and manipulate samples of ultra-cold atoms; thus, it's appropriate to start with how we get those atoms in the first place. This will be a very quick background on the basic force used to make atoms cold, and then the technology of atom sources for a variety of experiments.
Okay, so you've got two things in the post title. Which are we going to talk about first? Well, the study of cold atoms really begins with the observation that light can be used to push atoms around. There are actually two ways to do that, but…
drorzel | July 30, 2013I have a small collection of recent research papers that I'd like to write up open in various browser tabs and suchlike, but many of these would benefit from having some relatively clear and compact explanations of the underlying techniques. And while I can either dig up some old posts, or Google somebody else's, it's been a while since I wrote some simple, straightforward explanations of physics techniques, so I thought it'd be fun to write up some new explanations for use in future posts. Thus, this introduction to a series of techniques commonly used in my corner of Atomic, Molecular, and…
drorzel | July 25, 2013The other day, I made a suggestion to one of my research students of an experiment to try. When I checked back a day later, she told me it hadn't worked, and I immediately realized that what I had told her to do was very stupid. As penance, then, I'll explain the underlying physics, which coincidentally has a nice summer-y sort of application alluded to in the post title.
If you're the sort of person who enjoys swimming, and can either open your eyes underwater or regularly wear a mask or goggles, you've probably notice that the underside of the surface of a swimming pool or other body of…
drorzel | July 23, 2013I'm doing edits on the QED chapter of the book-in-progress today, and I'm struck again by the apparent randomness of the way credit gets attached to things. QED is a rich source of examples of this, but two in particular stand out, one experimental and the other theoretical.
On the experimental side, it's interesting to note that one of the two experimental effects that really galvanized the theoretical effort leading to QED bears the name of a particular person, while the other does not. Ask any physicist about the origin of QED, and they will almost certainly be able to cite the "Lamb shift…
drorzel | July 15, 2013One thing I left out of the making-of story about the squeezed state BEC paper last week happened a while after publication-- a few months to a year later. I don't quite recall when it was-- I vaguely think I was still at Yale, but I could be misremembering. It's kind of amusing, in an exceedingly geeky way, so I'll share it, though it's also a story of an embarrassing mis-step on my part.
So, the physical situation we were studying is described by the "Bose-Hubbard Hamiltonian": Bose because it's dealing with bosons (there's also a Fermi-Hubbard version, I believe); Hubbard after [mumble]…
drorzel | July 11, 2013Yesterday's write-up of my Science paper ended with a vague promise to deal some inside information about the experiment. So, here are some anecdotes that you would need to have been at Yale in 1999-2000 to pick up. We'll stick with the Q&A format for this, because why not?
Why don't we start with some background? How did you get involved in this project, anyway? I finished my Ph.D. work at NIST in early 1999, graduating at the end of May. I needed something to do after that, so I started looking for a post-doc by the don't-try-this-at-home method of emailing a half-dozen people I knew…
drorzel | July 10, 2013In Monday's post on squeezed states, I mentioned that I really liked the question because I had done work on the subject. This is, in fact, my claim to scientific fame (well, before the talking-to-the-dog thing, anyway)-- I'm the first author on a Science paper with more than 500 citations having to do with squeezed states. And since I've never written it up on the blog before, I'll leap on this opportunity to do some shameless self-promotion...
Well, aren't we Mr. Ego today? What's this paper that you're so impressed with about? I've never been all that good with titles, but I like to think…
drorzel | June 26, 2013 I'm always a little ambivalent about writing up papers that have also been written up in Physics: on the one hand, they make a free PDF of the paper available, which allows me to reproduce figures from the paper in my post, since I'm not breaking a paywall to do it. Which makes it much more attractive to write these up. On the other hand, though, they do a pretty good job writing accessible descriptions, so there's not that much for me to add.
In the case of this paper, I'll write it up anyway (albeit somewhat more briefly than usual, because they already did a nice job), just because the…
drorzel | June 13, 2013A few months back, I got a call from a writer at a physics magazine, asking for comments on a controversy within AMO physics. I read a bunch of papers, and really didn't quite understand the problem; not so much the issue at stake, but why it was so heated. When I spoke to the writer (I'm going to avoid naming names as much as possible in this post, for obvious reasons; anyone I spoke to who reads this is welcome to self-identify in the comments), he didn't really get it, either, and after kicking it around for a while, it failed to resolve into a story for either of us-- in his case, because…
drorzel | June 12, 2013Hey, dude? Yeah, what's up?
I'm not normally the one who initiates this, but I was wondering: When you were at DAMOP last week, did you see any really neat physics? Oh, sure, tons of stuff. It was a little thinner than some past meetings-- a lot of the Usual Suspects didn't make the trip-- but there were some really good reports from a lot of groups.
Anything really surprising? Well, there was one talk that I really liked a lot, that I went to on a lark, because I didn't understand what the session title could possibly mean, and there was no abstract for the talk: Experimental Studies of…
drorzel | June 4, 2013A little while back, I posted about the pro-theorist bias in popular physics, and Ashutosh Jogalekar offers a long and detailed response, which of course was posted on a day when I spent six hours driving to Quebec City for a conference. Sigh.
Happily, ZapperZ and Tom at Swans On Tea offer more or less the response I would've if I'd had time and Internet connectivity. Tom in particular gives a very thorough exploration of some of the reasons why experiment gets downplayed in popular physics. I particularly liked this bit:
I’m going to put forth a possibility: maybe we have a harder job, in…
drorzel | May 21, 2013At Scientific American's blog network, Ashutosh Jogalekar muses about the "greatest American physicist", eventually voting for Josiah Willard Gibbs, one of the pioneers of statistical mechanics. As both times I took StatMech (as an undergrad and in grad school), it was at 8:30 in the morning, I retain almost no memory of the subject, and will bow to greater experience in assessing Gibbs's importance.
I do, however, want to take issue with one thing in the post. When assessing the historical place of American physics, he writes:
Here’s my personal list for the title of greatest American…
drorzel | April 29, 2013Last year, Alan Alda posed a challenge to science communicators, to explain a flame in terms that an 11-year old could understand. this drew a lot of responses, and some very good winners. This year's contest, though still called the "Flame Challenge," asked for an answer to the question "What Is Time?"
This is a little closer to my corner of science, so I considered entering, but as previously noted, I'm crushingly busy at present. And either scripting/ shooting/ editing a video, or doing the necessary work to hack a written response down to the prescribed 300 characters was more time than I…
drorzel | March 26, 2013It's been a while since I've done a post over-analyzing some everyday situation, because I've been too busy to do any silly experiments. We're on break this week, though, so I took a little time Monday to bring excessive technology to bear on the critically important scientific question: how good is my insulated Starbucks cup?
To back up a little bit, because it's always important to provide background and motivation when writing a lab report, I spend a lot of time working at Starbucks these days, because when I try to get work done in my office, people keep showing up wanting me to do stuff…
drorzel | March 21, 2013Yesterday's big post on why I think people should embrace scientific thinking in a more conscious way than they do already (because my claim is that most people already use scientific thinking, they're just not aware that they're doing it) is clearly a kind of explanation of the reason behind my next book, but what about the previous two? How does teaching people about modern physics through imaginary conversations with my dog serve the general goal of getting people to think more scientifically?
The following is a bit of a retcon-- after all, the proximate cause of my writing those books was…
drorzel | January 18, 2013As research for the work-in-progress, I recently read Luis Alvarez's autobiography, Alvarez: Adventures of a Physicist, which contains a passage that I was reminded of last night while reading another book, that seems like an amusing follow-up to yesterday's rant about theory and experiment. This is from the end of the chapter where he joined Ernest Lawrence's Radiation Lab at Berkeley, and found he needed to get up to speed on a lot of physics he'd missed learning at the University of Chicago:
The other important component to my self-help program was a detailed study of three articles that…
drorzel | January 17, 2013There's been a bunch of talk recently about a poll on quantum interpretations that showed physicists badly divided between the various interpretations-- Copenhagen, Many-Worlds, etc.-- a result which isn't actually very surprising. Sean Carroll declares that the summary plot is "The Most Embarrassing Graph in Modern Physics, which I think is a bit of an overreaction, but not too much of one. I do strongly disagree with one thing he says in explaining this, though:
Not that we should be spending as much money trying to pinpoint a correct understanding of quantum mechanics as we do looking for…
drorzel | January 14, 2013Last week's post talked about the general idea of negative temperature, with reference to this much-talked-about Science paper (which also comes in a free arxiv version from which the figures used here are taken). I didn't go into the details of how they made a negative temperature gas, though, and as it's both very clever and hard to follow, I figure that deserves a post of its own.
Right, so last time you said that negative temperature just means you're more likely to find fast-moving atoms than slow ones, so all they need to do is whack these atoms in the right way? Right? No, it's more…