Quantum Optics
drorzel | May 5, 2011NASA held a big press conference yesterday to announce that the Gravity Probe B experiment had confirmed a prediction of General Relativity that spacetime near Earth should be "twisted" by the Earth's rotation. A lot of the coverage has focused on the troubled history of the mission (as did the press conference, apparently), but scientifically it's very impressive.
The shift measured is very, very small-- 0.04 arcseconds over the course of a year, or 0.000011 degrees-- but agrees nicely with the predictions of relativity. I'm not sure whether to try to work this into the book-in-progress as I…
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 23, 2011I am less enthralled by the "molecular gastronomy" thing than someone with my geek credentials ought to be. As a result, I was a little disappointed when I clicked the link (from Jennifer Ouellette on Twitter) to this Wired story about a new tv show called Marcel's Quantum Kitchen. Because, you know, there are much more fun things that the combination of "Quantum" and "Kitchen" could evoke:
A kitchen whose dishes all come in discrete and indivisible portions. You can't eat half and take the other half home-- it's all or nothing...
You can either know what you're making, or how long it will…
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…
drorzel | February 16, 2011Sean Carroll and Brad DeLong have each recently asserted that relativity is easier to understand than quantum mechanics. Both quote Feynman saying that nobody understands quantum mechanics, but Sean gives more detail:
"Hardness" is not a property that inheres in a theory itself; it's a statement about the relationship between the theory and the human beings trying to understand it. Quantum mechanics and relativity both seem hard because they feature phenomena that are outside the everyday understanding we grow up with. But for relativity, it's really just a matter of re-arranging the concepts…
drorzel | January 18, 2011The latest snowstorm is wreaking some havoc on my plans for the day, which means I'm going to lift another question and answer from the Physics Stack Exchange, with some modification. This one is a question about thermal radiation:
What are the quantum mechanisms behind the emission and absorption of thermal radiation at and below room temperature? If the relevant quantum state transitions are molecular (stretching, flexing and spin changes) how come the thermal spectrum is continuous? What about substances (such as noble gases) which don't form molecules, how do they emit or absorb thermal…
drorzel | January 12, 2011Another response copied/adapted from the Physics Stack Exchange. The question was:
What are the main practical applications that a Bose-Einstein condensate can have?
Bose Einstein Condensation, for those who aren't familiar with it, is a phenomenon where a gas of particles with the right spin properties cooled to a very low temeprature will suddenly "condense" into a state where all of the atoms in the sample occupy the same quantum wavefunction. This is not the same as cooling everything to absolute zero, where you would also have everything in the lowest energy state-- at the temperatures…
drorzel | December 28, 2010It's the last week of the (calendar) year, which means it's a good time to recap the previous twelve months worth of scientific news. Typically, publications like Physics World will publish a list of top ten physics stories of 2010, but we're all Web 2.0 these days, so it seems more appropriate to put this to a poll:
What is the top physics story of 2010?survey software
I've used the Physics World list as a starting point, because you have to start somewhere. I added a few options to cover the possibility that they left something out, and, of course, you know where the comments are.
This…
drorzel | December 15, 2010I've mentioned before that I'm answering the occasional question over at the Physics Stack Exchange site, a crowd-sourced physics Q&A. When I'm particularly pleased with a question and answer, I'll be promoting them over here like, well, now. Yesterday, somebody posted this question:
Consider a single photon (λ=532 nm) traveling through a plate of perfect glass with a refractive index n=1.5. We know that it does not change its direction or other characteristics in any particular way and propagating 1 cm through such glass is equivalent to 1.5 cm of vacuum. Apparently, the photon…
drorzel | December 10, 2010I'm currently working on a book about relativity, but I still spend a fair amount of time thinking about quantum issues. A lot of this won't make it into the book, because I can't assume people will have read How to Teach Physics to Your Dog before reading whatever the relativity book's title ends up being, and because explaining the quantum background would take too much space. But then, that's what I have a blog for...
Anyway, the section I was working on yesterday concerned causality and faster-than-light travel, specifically the fact that they don't play well together. Given Tuesday's…
drorzel | December 7, 2010Today is the official release date for the paperback edition of How to Teach Physics to Your Dog, so I wanted to write up something cool about quantum physics to mark the occasion. I looked around the house for inspiration, and most of what we have lying around the house is SteelyKid's toys. Thus, I will now explain the physics of quantum teleportation using SteelyKid's toys:
"Wait, wait, wait... You're not seriously planning to explain something quantum without me, are you?"
"I could hardly expect to get away with that, could I. No, I'm happy to have your contributions-- the book is about…
drorzel | December 1, 2010I hadn't heard anything about Dance of the Photons: From Einstein to Quantum Teleportation before it turned up in my mailbox, courtesy of some kind publicist at Farrar, Straus, and Giroux, otherwise I would've been eagerly anticipating it. Anton Zeilinger is a name to conjure with in quantum optics, having built an impressive career out of doing laboratory demonstrations of weird quantum phenomena. He shared the Wolf Prize earlier this year with John Clauser and Alain Aspect, and the three of them are in a small set of people who probably ought to get a Nobel at some point in the near future…
drorzel | November 19, 2010Earlier this week, I talked about the technical requirements for taking a picture of an interference pattern from two independent lasers, and mentioned in passing that a 1967 experiment by Pfleegor and Mandel had already shown the interference effect. Their experiment was clever enough to deserve the ResearchBlogging Q&A treatment, though, so here we go:
OK, so why is this really old experiment worth talking about? What did they do? They demonstrated interference between two completely independent lasers, showing that when they overlapped the beams, the overlap region contained a pattern…
drorzel | November 12, 2010As mentioned in yesterday's post on ion trapping, a month or so back Dave Wineland's group at NIST published a paper in Science on using ultra-precise atomic clocks to measure relativistic effects. If you don't have a subscription to Science, you can get the paper for free from the Time and Frequency Division database, because you can't copyright work done for the US government.
This paper generated quite a bit of interest when it came out, because it demonstrates the time-slowing effects of relativity without any need for exotic objects like black holes or particle accelerators-- they deal…
drorzel | November 6, 2010Having written in defense of analogies in physics yesterday, I should note that not all of the analogies that are brought out in an attempt to clarify physics concepts are good. For example, there's this incredibly strained opening to a Science News article on entanglement:
If the Manning brothers were quantum physicists as well as NFL quarterbacks, one of them could win his game's opening coin toss every time. The night before they played, the brothers would take two coins from a special quantum box to use the next day. If Peyton's game came first, after learning the outcome of his coin toss…
drorzel | November 5, 2010Regular commenter onymous left a comment to my review of Warped Passages that struck me as a little odd:
The extended analogy between the renormalization group and a bureaucracy convinced me that she was trying way too hard to make sophisticated concepts comprehensible. Also, I'm not really sure that analogies are the best way to explain concepts to people without using mathematics.
I'm not talking about the implication that making sophisticated concepts comprehensible is not worth doing, but rather the negativity toward analogies. It's odd because, if you think about it, a huge chunk of…
drorzel | October 15, 2010A big and important argument about religion and science has flared up again on Twittter. It occurs to me, though, that nobody has taken the obvious step of polling people about their actual beliefs, so let's see if we can't settle this question with (social) SCIENCE!:
I would prefer to be a member of:Market Research
What? It's not like this is any more pointless than the actual science-and-religion argument that's going on in blogdom.
drorzel | October 2, 2010A quick check-in from Tuscaloosa, where we're getting ready to head out for the football tailgating. While I've got a minute, though, here are the slides from my public lecture, via SlideShare:
What Every Dog Should Know About Quantum Physics
View more presentations from Chad Orzel.
These are probably less comprehensible that some of my other talks, as I deliberately avoided putting much text on the slides, which I think works better for this kind of presentation. The down side, of course, is that it's not as obvious what some of the slides mean, if you don't know the intended flow of the…
drorzel | September 13, 2010A fairly straightforward question: quantum physicists divide the world into two categories of things, fermions and bosons. What's your favorite object having integer spin?
What's your favorite boson?online survey
Superpositions of answers, while allowed in properly symmetrized wavefunctions, are not valid responses to this poll.