Experiment
drorzel | January 25, 2010There was a flurry of stories last week about an arxiv preprint on optical trapping of an ion. Somewhat surprisingly for an arxiv-only paper, it got a write-up in Physics World. While I generally like Physics World, I have to take issue with their description of why this is interesting:
In the past, the trapping of atomic particles has followed a basic rule: use radio-frequency (RF) electromagnetic fields for ions, and optical lasers for neutral particles, such as atoms. This is because RF fields can only exert electric forces on charges; try to use them on neutral particles and there's…
drorzel | January 25, 20102010 marks the 50th anniversary of the invention of the laser. To mark the occasion, the American Physical society has launched LaserFest, which will involve a large number of public events over the next year. The website includes a bunch of cool things explaining the physics of lasers, and a timeline of laser history with one glaring bug that you'll have to figure out for yourself. Over at Cocktail Party Physics, Jennifer Ouellette has an excellent historical survey of her own, saving me a lot of typing.
(Fun fact: Gordon Gould, who eventually won a lengthy patent fight, was a Union alumnus…
drorzel | January 19, 2010Consider the air around you, which is hopefully at something like "room temperature"-- 290-300 K (60-80 F). That temeprature is a measure of the kinetic energy of the moving atoms and molecules making up the gas. At room temperature, the atoms and molecules in the air around you are moving at something close to the speed of sound-- around 300 m/s (give or take a bit, depending on the mass).
If you're a physicist or chemist looking to study the property of these atoms and molecules, that speed is kind of a nuisance. For one thing, the atoms and molecules tend not to stick around long enough to…
drorzel | January 19, 2010Consider the air around you, which is hopefully at something like "room temperature"-- 290-300 K (60-80 F). That temeprature is a measure of the kinetic energy of the moving atoms and molecules making up the gas. At room temperature, the atoms and molecules in the air around you are moving at something close to the speed of sound-- around 300 m/s (give or take a bit, depending on the mass).
If you're a physicist or chemist looking to study the property of these atoms and molecules, that speed is kind of a nuisance. For one thing, the atoms and molecules tend not to stick around long enough to…
drorzel | January 18, 2010Before leaving Austin on Friday, I had lunch with a former student who is currently a graduate student at the University of Texas, working in an experimental AMO physics lab. I got the tour before lunch-- I'm a sucker for lab tours-- and things were pretty quiet, as they had recently suffered a catastrophic failure of a part of their apparatus.
Of course, there are catastrophic failures, and then there are catastrophic failures. Some dramatic equipment failures, like the incredible exploding MOSFET's when I was a post-doc, are just God's way of telling you to go home and get a good night's…
drorzel | January 11, 2010I was looking at some polling about science over the weekend, and discovered that they helpfully provide an online quiz consisting of the factual questions asked of the general public as part of the survey. Amusingly, one of them is actually more difficult to answer correctly if you know a lot about the field than if you only know a little. I'll reproduce it here first, if you would like to take a crack at it, and then I'll explain why it's tricky below the fold.
The global positioning system, or GPS, relies on which of these to work?(answers)
Choose only one answer-- this is being recorded…
drorzel | January 9, 2010One of the few sad things about the recent American domination of physics (says the American physicist) is that new physical phenomena are now mostly given boring, prosaic American English names. Don't get me wrong, I like being able to pronounce and interpret new phenomena, but when the pre-WWII era of European dominance faded away, we lost those awesome German names. Like, for example, zitterbewegung, a word that just demands an exclamation point: Zitterbewegung!
The phenomenon it describes, ironically, comes out of work by the great English physicist and odd duck Paul Dirac. Dirac's…
drorzel | January 7, 2010A number of people have commented on this LA Times op-ed by Steve Giddings about what physicists expect to come out of the Large Hadron Collider. It includes a nice list of possible particle physics discoveries plus a few things that will annoy Peter Woit, and also includes the obligatory note about spin-offs:
All this may seem like impractical and esoteric knowledge. But modern society would be unrecognizable without discoveries in fundamental physics. Radio and TV, X-rays, CT scans, MRIs, PCs, iPhones, the GPS system, the Web and beyond -- much that we take for granted would not exist…
drorzel | January 5, 2010"Slow light" is in the news again. The popular descriptions of the process usually leave a lot to be desired, so let's see if we can't do a slightly better job of explaining what's going on. The key idea is using one light beam to control the transmission of another.
Let's say you have a bunch of atoms in a gas and a laser. The laser happens to be at exactly the right frequency to be absorbed by the atoms, meaning that if you try to shine the laser through the gas, it'll be absorbed, and won't make it out the other side. This is traditionally represented by a diagram like to one to the right…
drorzel | January 4, 2010I spent most of Saturday in the lab, swapping out a turbopump that was starting to die. How could I tell? Well, for one thing, it made an awful noise, even more than usual for a noisy pump. But after it was stopped and unmounted from the chamber, there was a simple test: comparing the rotation to a second pump that I knew was in better shape:
The pump on the left (with the copper gasket stuck to it) is the old one; the pump on the right is the one that I replaced it with. As you can tell, even with a bearing starting to go, it's a pretty damn good rotor, but clearly worse than the…
drorzel | January 4, 2010Let's say you have some liquid that you want to contain without leaks, say, milk for a baby. What do you do?
Well, you put it in something like a baby bottle, the components of which are shown here:
You have a hard plastic bottle, a soft silicone nipple, and a hard plastic ring that screws onto the bottle. When you put it together and screw the cap down tight, it compresses the silicone between the two plastic bits, squeezing it into the small gaps, and plugging any leaks. Done properly, this will ensure that milk doesn't leak out of the bottle except through the whole in the nipple.
Now,…
drorzel | December 18, 2009As a physicist with a blog, I am contractually obligated to do a post on the CDMS almost-a-result. This is that post.
The short version: they expected at most 0.8 events (that's total events, not events per day, or anything-- this is a whole community built on detecting nothing at all), and got 2, with maybe a third that was close to making the cut, but didn't. I think Joe Fitzsimons on Twitter summed it up best, writing:
Isn't that the least informative number of events possible?
It's more events than expected, but not enough to really be meaningful. The probability of this level of signal…
drorzel | December 11, 2009One of the things I forgot to mention in yesterday's post about why I like AMO physics is that AMO systems have proven to be outstanding tools for solving problems from other fields of physics. In particular, ultra-cold atoms have proven to be a fantastic venue for studying problems from condensed matter physics. There's a comprehensive review of the subject in this Reviews of Modern Physics paper, which is also freely available on the arxiv. I say "comprehensive review," but, of course, it's almost certainly already out of date, given how much work is going on in this area.
To understand why…
drorzel | December 10, 2009Months ago, during the DonorsChoose fundraiser, I offered to answer questions from people who donated to the Challenge. I then promptly forgot to respond to the questions sent in. Mea maxima culpa. Here's a way-too-late response to a good question from "tcmJOE":
I've spent the past few years trying to explore physics and figure out what I would be interested in doing--I've settled more towards energy research, somewhere between CM and MatSci, but I've tried at a variety of different things in the along the way. So my question for you is: How did you end up in AMO? Were there any other fields…
drorzel | December 2, 2009I've made a couple of oblique references to this over the past couple of months, but I have an article in the new issue of Physics World, on experiments using molecules to search for an electric dipole moment of the electron:
When most of us think about searching for physics beyond the Standard Model - the dominant paradigm of particle physics - the first thing that springs to mind is probably a gigantic particle accelerator like CERN's Large Hadron Collider (LHC). Within the collider's 27-km loop, protons slam together at 99.9999991% of the speed of light. Office-building-sized detectors…
drorzel | November 6, 2009Today's Quantum Optics lecture is about quantum computing experiments, and how different types of systems stack up. Quantum computing, as you probably know if you're reading this blog, is based on building a computer whose "bits" can not only take on "0" and "1" states, but arbitrary superpositions of "0" and "1". Such a computer would be able to out-perform any classical computer on certain types of problems, and would open the exciting possibility of a windows installation that is both working and hung up at the same time.
There are roughly as many types of proposed quantum computers as…
drorzel | November 2, 2009One of my pet peeves about physics as perceived by the public and presented in the media is the way that everyone assumes that all physicists are theoretical particle physicists. Matt Springer points out another example of this, in this New Scientist article about the opening panel at the Quantum to Cosmos Festival. The panel asks the question "What keeps you up at night?" and as Matt explains in detail most of the answers are pretty far removed from the concerns of the majority of physicists.
But it's a good question even for low-energy experimentalists like myself, as it highlights the…
drorzel | October 15, 2009I gave a guest lecture this morning in a colleague's sophomore seminar class about time. She's having them look at time from a variety of perspectives, and they just finished reading Longitude, so she asked me to talk about the physics of clocks and the measurement of time.
I've long considered using "A Brief History of Timekeeping" as the theme for a general education course-- there's a ton of interesting science in the notion of time and timekeeping. This was just a single class, though, so I didn't go into too much detail:
A Brief History of Timekeeping
View more presentations from Chad…
drorzel | October 6, 2009The sneaky folks at the Nobel Foundation have thrown a spanner in the works when it comes to the Physics prize. All the speculation has surrounded exotic quantum effects and theoretical esoterica, and they turn around and give it to something -gasp- practical...
The 2009 Nobel Prize in Physics is split three ways: half to Charles K. Kao "for groundbreaking achievements concerning the transmission of light in fibers for optical communication," and the other half to Willard S. Boyle and George E. Smith "for the invention of an imaging semiconductor circuit - the CCD sensor."
Now these aren't…
drorzel | September 22, 2009Buried in the weekend links dump at the arxiv blog was Scalable ion traps for quantum information processing:
We report on the design, fabrication, and preliminary testing of a 150 zone array built in a `surface-electrode' geometry microfabricated on a single substrate. We demonstrate transport of atomic ions between legs of a `Y'-type junction and measure the in-situ heating rates for the ions. The trap design demonstrates use of a basic component design library that can be quickly assembled to form structures optimized for a particular experiment.
At first glance, this isn't a sexy paper…