Quantum Optics
drorzel | November 17, 2009Sunday night, the Patriots lost a heartbreaker to the Colts 35-34. The talk of the sports world yesterday was Bill Belichick's decision to go for it on fouth-and-two on his own 28 yard line when he was up by six with just over two minutes to play. They didn't get the first down, and turned the ball back over to the Colts, who went on to score a touchdown and win the game.
Yesterday's discussion was a low point even by the standards of sports talk radio, with one idiot after another holding forth about how stupid Belichick's decisions was, and how he "disrespected his defense," and various…
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 | October 14, 2009Both Physics Buzz and the X-Change Files are noting the Imagine Science Film Festival starting tomorrow in New York City. As the Buzz notes:
This is only the film festival's second year, but it's already attracted the attention of major sponsors. Last year the journal Nature co-sponsored the festival, and this year the American Association for the Advancement of Science, publisher of rival journal Science, has taken the helm. Maybe it's because of the festival's unique approach to the genre of science film.
Unlike what you can expect to see on PBS NOVA or the Discovery Channel, these films…
drorzel | October 13, 2009The abbreviation here has a double meaning-- both "Open Access" and "Operator Algebra." In my Quantum Optics class yesterday, I was talking about how to describe "coherent states" in the photon number state formalism. Coherent states are the best quantum description of a classical light field-- something like a laser, which behaves very much as if it were a smoothly oscillating electromagnetic field with a well-defined frequency and phase.
Mathematically, one of the important features of a coherent state is that it is unchanged by the photon annihilation operator (in formal terms, it's an "…
drorzel | October 7, 2009Prompted by working on lecture notes for Quantum Optics last night, a Dorky Poll about the mathematical formalism of photon number states
What's your favorite photon operator?(polls)
I know it's hard to pick, but choose only one.
drorzel | October 2, 2009Via His Holiness, there is an aggressively stupid paragraph in a New York Times movie review today:
Did you hear the one about the guy who lived in the land of Uz, who was perfect and upright and feared God? His name was Job. In the new movie version, "A Serious Man," some details have been changed. He's called Larry Gopnik and he lives in Minnesota, where he teaches physics at a university. When we first meet Larry, in the spring of 1967, his tenure case is pending, his son's bar mitzvah is approaching, and, as in the original, a lot of bad stuff is about to happen, for no apparent reason.…
drorzel | October 2, 2009I'm teaching my Quantum Optics class again this term, out of a completely different textbook than last time around-- I'm using Mark Fox's Quantum Optics from the Oxford Master Series in AMO Physics, which is more of a regular textbook. I've got six students-- four junior and senior physics majors, one senior chemistry major, and a retired scientist from GE who is interested in catching up on the latest new stuff.
Last time around, I posted my lecture notes as I went through the class, but I've forgotten to do that thus far this term, here in the Freezing Hell of Lab Grading. So here's a big…
drorzel | September 18, 2009I'm teaching Quantum Optics again this term, talking about the interaction between light and matter in circumstances where you need to account for the quantum nature of one or both of those. We're starting on the actual interactions today, albeit with a semi-classical approach (Einstein coefficients and the Fermi Golden Rule), but we've just finished a whirlwind review of quantum mechanics, including a rapid survey of the different effects that determine atomic energy levels, and some of the ways we have to move those around.
This suggests a really dorky idea for a poll, so:
What's your…
drorzel | September 15, 2009The ArXiV Blog and several other sources last week linked to a new paper titled Towards Quantum Superposition of Living Organisms:
The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. Up to now, the existence of such states has been tested with small objects, like atoms, ions, electrons and photons, and even with molecules. Recently, it has been even possible to create superpositions of collections of photons, atoms, or Cooper pairs. Current progress in optomechanical systems may soon…
drorzel | August 27, 2009I'm feeling slightly better, but still a little wobbly, so here's what may be the dorkiest Dorky Poll yet:
How do you like your quantum mechanics?(trends)
drorzel | August 13, 2009One of our poetry contest winners has been reading his proof copy of How to Teach Physics to Your Dog, and posted some comments. Actually, it was posted last week, but I was at Worldcon, and not dealing with much of anything else.
The comments are pretty positive, but he asks a couple of questions along the way, and I figured I should respond to those here. So, below the fold are Adrian's questions and my responses:
I don't get what's so weird about the Quantum Eraser, other than things that are already weird in simpler double-slit experiments in any case. Once you've accepted that a photon…
drorzel | August 3, 2009Last weekend, I was talking with Ethan Zuckerman at a party, and we talked a little bit about the TED conferences and similar things. A few days later, there was an editorial in Nature suggesting that scientists could learn a lot from TED:
[P]erhaps the most critical key to success is the style of the talks. And here, those scientists wishing to inspire public audiences could take a few tips from the speakers in Oxford who addressed themes as various as biomimicry (Janine Benyus), the neuroscience of other people's rational and moral judgements (Rebecca Saxe) and supermassive black holes (…
drorzel | July 29, 2009The Corporate Masters have launched a "featured blogger" program, asking individual ScienceBloggers to comment on news articles from the main site, and publishing the responses with the magazine piece. I just did one on new quantum experiments, which was posted today.
The news article is Supersizing Quantum Behavior by Veronique Greenwood. My piece is Reconciling an Ordinary World, which starts out:
One of the most vexing things about studying quantum mechanics is how maddeningly classical the world is. Quantum physics features all sorts of marvelous things--particles behaving like waves,…
drorzel | July 27, 2009Timothy Burke notes a controversy about an NEH program that some philosophers feel tramples their discipline. In talking about a hypothetical program that would do the same for his field of history, Burke suggests something that caught my eye:
f the NEH set up a course development grant called "Time and the Past" aimed at supporting interdisciplinary courses that examined change over time but framed the grant so that ordinary history courses didn't qualify, my first impulse would be to object. Why exclude the discipline that makes that question its central concern?
But hold on a moment. What…
drorzel | July 15, 2009Yesterday's Michelson Interferometer quiz was surprisingly popular-- as of 8:30 pm Tuesday (when I'm writing this), just under 1500 people have voted in the poll, three and a half times as many as in the next most popular poll I've done. Who says there's no audience for physics?
So, what's the right answer, you ask?
The correct answer finished a distant second (as of 8:30 it has 21% of the votes, to 52% for the leading wrong answer). The answer is that the light goes back where it came from. Bob Hawkins and MattXIV have the right explanation: on the return trip, half of each beam goes to the…
drorzel | July 14, 2009Inspired by one of yesterday's easy questions, a pop quiz for you. The figure below shows a Michelson Interferometer:
A laser falls on a beamsplitter, which allows half of the light to pass straight through, and reflects the other half downward. Each of those beams then hits a mirror that reflects it directly back where it come from. The beams are recombined at the beamsplitter, and then fall on the viewing screen at the top of the figure.
When we add together the light from the two paths, we find that if the lengths of the two arms (that is, the distance from beamsplitter to mirror) are…
drorzel | July 7, 2009It's been a while since we've had any good, solid physics content here, and I feel a little guilty about that. So here's some high-quality (I hope) physics blogging, dealing with two recent(ish) papers from Chris Monroe's group at the University of Maryland. The first is titled "Bell Inequality Violation with Two Remote Atomic Qubits" (and a free version can be found on the Arxiv); the second is "Quantum Teleportation Between Distant Matter Qubits" (and isn't available on the arxiv because it's in Science, but you can get it from their web site). Both of these deal with the physics of…
drorzel | June 5, 2009Physics World posted a somewhat puzzling story a few days back, headlined Ultra cold atoms help share quantum information:
Scientists in the US have demonstrated a novel "light-switch" in an optical fibre that could become a new tool in the communications industry. The device created by Michal Bajcsy at Harvard University and colleagues could be developed to share both classical and quantum information.
Quantum information systems could bring a revolution to global data-sharing, by encrypting, processing, and transmitting information using the properties of quantum mechanics. However, as…
drorzel | June 5, 2009Physics World reports on the awarding of a major French prize in science:
A physicist has been awarded France's top science prize for his work on atomic physics and quantum optics. Serge Haroche -- one of the founding fathers of cavity quantum electrodynamics (QED) -- was presented with this year's "gold medal" by the French national research council (CNRS) at a press conference in Paris yesterday. Haroche currently heads the electrodynamics and simple systems group at CNRS's Kastler Brossel Lab in Paris.
Previous physics recipients include the Nobel Prize winners Albert Fert and Claude Cohen…
drorzel | May 21, 2009Thursday at DAMOP was a little more broken up than usual for me at one of these meetings, because the nagging cold I have was bugging me more, and also because I needed to check my email a few times. There was still some neat stuff, though.
The early-morning session was the toughest call of the meeting: there was the undergraduate research session, a session on ultracold Rydberg atoms, and a session on complicated states in BEC, in widely spaced locations. I ended up skipping the undergraduate session in favor of hearing Chris Foot talk about a rotating optical lattice (which simulates some…