Optics
drorzel | August 8, 2013This topic is an addition to the original list in the introductory post for the series, because I had thought I could deal with it in one of the other entries. Really, though, it deserves its own installment because of its important role in the history of laser cooling. Laser cooling would not be as important as it is now were it not for the fact that cooling below the "Doppler limit" in optical molasses is not only possible, but easy to arrange. That's thanks to the "Sisyphus cooling" mechanism, the explanation of which was the main reason Claude Cohen-Tannoudji got his share of the 1997…
drorzel | August 6, 2013Last time in our trip through the cold-atom toolbox, we talked about light shifts, where the interaction with a laser changes the internal energy states of an atom in a way that can produce forces on those atoms. This allows the creation of "dipole traps" where cold atoms are held in the focus of a laser beam, but that's only the simplest thing you can use light shifts for. One of the essential tools of modern atomic physics is the "optical lattice," which uses patterns of light to make patterns of atoms.
OK, what do you mean "patterns of light"? Well, remember, light has both wave and…
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 12, 2013I spend a lot of time promoting Rhett Allain's Dot Physics blog, enough that some people probably wonder if I get a cut of his royalties (I don't). I'm going to take issue with his latest, though, because he's decided to revive his quixotic campaign against photons, or at least teaching about photons early in the physics curriculum. We went through this back in 2008 and 2009 (though Rhett's old posts are linkrotted away, so you only get my side of the story...). I'm no more convinced this time around, even though he drags in Willis Lamb and David Norwood for support.
There are basically two…
drorzel | July 8, 2013In the Physics Blogging Request Thread the other day, I got a comment so good I could've planted it myself, from Rachel who asks:
It’s a term I see used a lot but don’t really know what it means – what is a “squeezed state”? What does “squeezing” mean? (in a QM context of course…)
I love this, not only because it gives me an excuse to talk about cool physics, but because it will let me engage in blatant self-promotion-- I have a Science paper on squeezed states, which I've never actually written up for the blog. So this post will be a great way to set up a future post, ResearchBlogging that…
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 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 | 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…
drorzel | November 27, 2012In which I unpack a cryptic paper title and explain how quantum superposition lets you use light to keep things from interacting with light.
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I joined AAAS a couple of years ago to get a break on the registration fee for their meeting, and I've kept up the membership mostly because I like having individual access to Science articles, so I can read them in the coffee shops where I get actual work done. This also gives me access to articles in the "advance online publication" stage, which is hilarious because Union's institutional subscription doesn't include those articles-- if I'…
drorzel | November 14, 2012OK, it's a paper I mentioned here before, when it went up on the arxiv, but the "Comments on Atomic, Molecular, and Optical Physics" article I wrote this summer is up on the Physica Scripta web site now, and for the next not-quite-thirty days it's free to read and download:
Searching for new physics through atomic, molecular and optical precision measurements
We briefly review recent experiments in atomic, molecular and optical physics using precision measurements to search for physics beyond the Standard Model. We consider three main categories of experiments: searches for changes in…
drorzel | October 11, 2012It's a banner day for science explainer things I wrote, as a piece I wrote has just gone live at Tor.com:
Why Gandalf Is Wrong
Even as a kid, reading J. R. R. Tolkien’s The Lord of the Rings at the golden age of twelve or so, Gandalf’s response to Saruman never sat well with me. Splitting white light into its component colors is awesome, and taking things apart is the best way to learn how they work. Knowing how things work is the first step toward making them work better, a process that leads to the technologies that make modern life comfortable enough to, among other things, provide Oxford…
drorzel | October 11, 2012In which we do a little imaginary Q&A to explain the significance of Tuesday's Nobel Prize to Dave Wineland and Serge Haroche.
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I did a quick post Tuesday morning noting that the latest Nobel Prize in Physics was awarded to two big names from my corner of the field. This would've been a great time to drop a long explainer post about what they did and why it's cool, but alas, I have a day job, and the Nobel committee stubbornly refuses to tell me who they're giving the prizes to in advance. Oh, well.
Still, I'm just vain enough to think I can add something a little different…
drorzel | October 5, 2012In which we do a little ResearchBlogging to look at a new paper about weird quantum effects, entangling two photons that never both exist at the same time.
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I'm teaching full-time this term, but I've blocked out Thursdays as a day when I don't do class- or chair-related work. Usually, this means trying to write something on the work-in-progress, but I finished a short thing in the morning that needed to sit for a few hours before I looked at it again, which left a nice opportunity for some blogging. And, conveniently, somebody retweeted a New Scientist story about an arXiv…
drorzel | June 19, 2012In which we look at a slightly crazy-sounding proposal from my former boss, the experimental realization of which is getting close to completion.
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I spent more or less the entire first day of DAMOP a couple of weeks ago going to precision measurement talks. Most of these were relatively sedate (at least by the standards of a sub-field that routinely involves people proposing incredibly difficult experiments), but my boss when I was at Yale, Mark Kasevich, provided the bold proposals I usually expect, in this case suggesting an experiment using an atom interferometer to measure…
drorzel | June 4, 2012In which we do a little ResearchBlogging, taking a look at a slightly confusing paper putting a new twist on the double-slit experiment.
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I'm off to California this afternoon, spending the rest of the week at DAMOP in Pasadena (not presenting this year, just hanging out to see the coolest new stuff in Atomic, Molecular, and Optical Physics). I don't want to leave the blog with just a cute-kid video for the whole week, though, so here's some had-core physics: a new paper in the Proceedings of the National Academy of Sciences (freely available online), looking at a new sort of…
drorzel | May 4, 2012Enough slagging of beloved popularizers-- how about some hard-core physics. The second of three extremely cool papers published last week is this Nature Physics paper from the Zeilinger group in Vienna, producers of many awesome papers about quantum mechanics. Ordinarily, this would be a hard paper to write up, becase Nature Physics are utter bastards, but happily, it's freely available on the arxiv, and all comments and figures are based on that version.
You're just obsessed with Zeilinger, aren't you? All right, what have they done this time? The title is "Experimental delayed-choice…