Optics
drorzel | April 2, 2012So, the infamous OPERA result for neutrino speeds seems to be conclusively disproven, traced to a problem with a timing signal. Matt Strassler has a very nice explanation of the test that shows that the whole thing can almost certainly be traced to a timing error that cropped up in 2008. This problem is generally described as resulting from a "loose fiber optic cable," and Matthew Francis's reaction is fairly typical
The main culprit was a fiber optic cable that was slightly out of alignment. This is not quite a "loose wire", as it sometimes has been described: it's far more subtle and harder…
drorzel | September 19, 2011I got a new comment on an old post asking an interesting question about thermodynamics:
I have a question that bears somewhat on this issue of keeping cars parked in the sun, cooler. You all know those accordion folded/aluminized shades you can put up inside the windshield and back window.
Seems to me putting them INSIDE is the wrong approach. They should be on the OUTside of the window acting as real shades and reflecting away the sun before it gets into the inside of the car.
This involves some of the same physics involved in the ever-popular issue of climate change, so it's worth talking…
drorzel | July 28, 2011A while back, I explained how polarized sunglasses work, the short version of which is that light reflected off the ground in front of you tends to be polarized, and by blocking that light, they reduce the effects of glare. This is why fishermen wear polarized sunglasses (they make it easier to see through the surface of water) and why they're good for driving (they cut down on glare off the road ahead). I almost exclusively buy polarized sunglasses, because I like this feature.
But let's say you have a pair of polarized sunglasses that broke, because they were cheap to begin with (such as…
drorzel | July 1, 2011Third of the five research categories within DAMOP that I talked about is Quantum Phenomena. This is a little bit of a catch-all, as there are a few different things going on in this area. They are all unified, though, by the fact that they end up making quantum mechanical effects manifest in some way, either as a means to an end, or just for the sake of showing that quantum mechanics is really weird.
What do I mean "making quantum mechanical effects manifest?" Basically, demonstrating one of the essential elements that I talked about last year: showing the wave nature of matter,…
drorzel | June 30, 2011The second in the DAMOP research categories I talked about is "Extreme Lasers," a name I was somewhat hesitant to use, as every time I see "Extreme [noun]," I get a flash of Stephen Colbert doing air guitar. It is, however, the appropriate term, because these laser systems push the limits of what's possible both in terms of the pulse duration (attosecond pulses are common, with 1as = 0.000000000000000001 s) and the pulse intensity (1014 W/cm2 is a typical order-of-magnitude, and some systems get much higher than that).
One of the main tricks for generating these ultra-short pulses is to do…
drorzel | June 29, 2011The first of the five categories of active research at DAMOP that I described in yesterday's post is "Ultracold Matter." The starting point for this category of research is laser cooling to get a gas of atoms down to microkelvin temperatures (that is, a few millionths of a degree above absolute zero. Evaporative cooling can then be used to bring the atoms down to nanokelvin temperatures, reaching the regime of "quantum degeneracy." This is, very roughly speaking, the point where the quantum wavelength of the atoms becomes comparable to the spacing between atoms in the gas, at which point the…
drorzel | June 28, 2011That's the title of my slightly insane talk at the DAMOP (Division of Atomic, Molecular, and Optical Physics of the American Physical Society) conference a couple of weeks ago, summarizing current topics of interest in Atomic, Molecular, and Optical Physics. I'll re-embed the slides at the end of this post, for anyone who missed my earlier discussion.
I put a ton of work into that talk, and had a huge amount of material that I didn't have time to include. I'd hate for that to go to waste, so I'm going to repurpose it for blog content over the next week or so. It'll probably be about a half-…
drorzel | June 16, 2011One of the odd things about going to conferences is the unpredictable difference between talks and papers. Sometimes, when you go to a talk, you just get an exact repetition of what's in the paper; other times, you get a new angle on it, or some different visual representations that make something that previously seemed dry and abstract really click. And, of course, sometimes you get new hot-off-the-apparatus results that haven't made it into print yet.
Maddeningly, there doesn't seem to be any way to know in advance which of these things you're going to get from the title and abstract. It…
drorzel | June 15, 2011Tuesday at DAMOP was dominated by my talk. Well, in my mind, at least. I suppose people who aren't me saw other interesting things.
OK, fine, I did go to some other sessions. I would link to the abstracts, but the APS web site is having Issues this morning.
In the Prize Session that always opens the meeting, Gerry Gabrielse from Harvard gave a really nice talk about his work on measuring the anomalous magnetic moment of the electron. This is the "g-factor" that I've cited before in calling quantum physics the most precisely tested theory in the history of science. Gabrielse is the guy behind…
drorzel | June 14, 2011That's the title of my talk this morning at DAMOP, where I attempt the slightly insane feat of summarizing a meeting with over 1000 presentations in a single 30-minute talk. This will necessarily involve talking a little bit like the person reading the legal notices at the end of a car commercial, and a few of the guide-to-the-meeting slides will have to flash by pretty quickly. Thus, for the benefit of those who have smartphones and care about my categorization of talks, I have put the slides on SlideShare in advance, and will embed them here:
What's So Interesting About AMO Phyiscs?…
drorzel | June 13, 2011You may or may not have noticed that I've been making a concerted effort to do more ResearchBlogging posts explaining notable recent results. I've been trying to get at least one per week posted, and coming fairly close to that. I've been pretty happy with the fake Q&A format that I've settled into, and while they're time-consuming to write, they're also kind of fun.
This past week, alas, was kind of brutal, as I was doing a ton of reading in preparation for my DAMOP talk tomorrow, which, in retrospect, is kind of insane, and SteelyKid's day care being closed for two days didn't help (…
drorzel | June 9, 2011One of the many things I've been occupied with the last few weeks has been arranging a reception at next week's Division of Atomic, Molecular, and Optical Physics (DAMOP) meeting. I was late in asking about the possibilities for this, so it won't make it to the printed program, which means I need to advertise by word of mouth. So:
What: An informal reception for people attending the DAMOP meeting who are associated with undergraduate institutions (i.e., small colleges, or non-Ph.D. granting universities), or thinking about pursuing a position at an undergraduate institution.
Why: Over the…
drorzel | June 7, 2011I have to admit, I'm writing this one up partly because it lets me use the title reference. It's a cool little paper, though, demonstrating the lengths that physicists will go to in pursuit of precision measurements.
I'm just going to pretend I didn't see that dorky post title, and ask what this is about. Well, it's about the trapping and laser cooling of thorium ions. They managed to load thorium ions into an ion trap, and use lasers to lower their temperature into the millikelvin range. At such low temperatures, the ions in the trap "crystallize."
So, they've demonstrated that if you get…
drorzel | June 3, 2011It's been a long and brutally busy week here, so I really ought to just take a day off from blogging. But there's a new paper in Science on quantum physics that's just too good to pass up, so here's a ReasearchBlogging post to close out the week.
Aw, c'mon, dude, I'm tired. What's so cool about this paper that it can't wait until next week? Well, the title kind of says it all: they measured the average trajectories of single photons passing through a double-slit apparatus. By making lots of repeated weak measurements at different positions behind the slits, they could reconstruct the average…
drorzel | May 13, 2011Back when I was an undergrad, we did a lab in the junior-level quantum class that involved making a dye laser. We had a small pulsed nitrogen laser in the lab, and were given a glass cell of dye and some optics and asked to make it lase in the visible range of the spectrum.
My partner and I worked on this for almost the entire lab period, and got nothing more than the occasional faint flicker of a green beam. We got the TA to help us, and he couldn't do any better. The TA went to get the professor teaching the class, but he was helping other students with one of the other experiments (this…
drorzel | May 4, 2011It's been a hectic day here, so I haven't had time to do any substantive blogging. I did want to quickly note a couple of stories presenting marked improvements in experiments I've written up here in the past:
1) In the "self-evident title" category, there's Confinement of antihydrogen for 1000 seconds, which extends last year's antihydrogen trapping to times a factor of 6000 longer than the previous record. That's very good, and a good sign for plans to do precision spectroscopy and other such experiments. As always, Physics World offers a nice write-up.
2) As noted in the comments of Monday…
drorzel | May 2, 2011Last summer, there was a fair bit of hype about a paper from Mark Raizen's group at Texas which was mostly reported with an "Einstein proven wrong" slant, probably due to this press release. While it is technically true that they measured something Einstein said would be impossible to measure, that framing is a little unfair to Einstein. It does draw media attention, though...
The experiment in question involves Brownian motion, and since I had to read up on that anyway for something else, I thought I might as well look up this paper, and write it up for the blog.
OK, so what did they do that…
drorzel | April 26, 2011This paper made a big splash back in November, with lots of news stories talking about it; it even made the #6 spot on Physics World's list of breakthroughs of the year. I didn't write it up then because I was hellishly busy, and couldn't take time away from working on the book-in-progress to figure out exactly what they did and why it mattered. I've got a little space now between handing the manuscript in last week and starting to revise it (probably next week), so while it's a bit late, here's an attempt at an explanation of what all the excitement was about.
So, what's this about, anyway?…
drorzel | April 18, 2011 It's been a while since I wrote up a ResearchBlogging post, but since a recent paper forced me to update my "What Every Dog Should Know About Quantum Physics" slides with new pictures, I thought I should highlight the work on the blog as well. Not that you could've missed it, if you follow physics-y news-- it's been all over, getting almost as much press as rumors that some people whose funding will run out soon saw something intriguing in their data. So, in the usual Q&A format:
OK, what's this about? Well, the paper title, "Quantum interference of large organic molecules" pretty well…
drorzel | March 11, 2011I've got three months to decide. I'll be giving an invited talk at the Division of Atomic, Molecular, and Optical Physics (DAMOP) with this title, with a goal of introducing the field to students and physicists from other fields:
In recent years, DAMOP has expanded to the point where the meeting can be quite daunting for a first-time attendee. This talk will provide an introduction to some of the most exciting current areas of research in Atomic, Molecular, and Optical physics, intended to help undergraduates, beginning graduate students, or physicists from other fields attending their first…