Quantum Optics
drorzel | May 21, 2009Technically, the meeting started Tuesday, but all that happened was a welcome reception, which I missed due to travel. The real beginning of the meeting was Wednesday morning, with the traditional unscheduled half-hour welcome from local dignitaries. That was followed by the Prize Session, featuring the frighteningly smart Misha Lukin, who was awarded the I.I. Rabi Prize for being really freaking brilliant. The abstract he sent in was kind of vague, but he mostly talked about stuff related to the quantum computing in diamond stuff that I've blogged about before.
I'm fighting a bit of a cold,…
drorzel | May 20, 2009I made it to Charlottesville, and am all checked in to the Econo Lodge, which is a little more Econo than I was expecting. It's an old-school motel, with rooms that open right into the parking lot, the sort of place where the towels are tiny and scratchy, the pillows and mattresses are thin, and the tap water tastes like cigarette smoke. Still, it's not like I'm going to be doing much more than sleeping here.
I promised some entertainment in my absence, so this seems like a good time for a Dorky Poll. I'm going to be spending a lot of time over the next few days listening to talks about the…
drorzel | May 7, 2009I was surprised, a few days ago, to see a post from ZapperZ recommending a Wall Street Journal article on quantum entanglement. It was surprising not only because it's weird to see anything in the WSJ that doesn't have an immediate financial connection, but more than that, I was surprised because the article contains a lot of statements that are the sort of thing ZapperZ usually denounces as unforgivable ignorance by journalists who shouldn't be allowed to write about science.
Happily, by sitting on the article for a couple of days, Tom said most of what I would've said, and I was saved…
drorzel | May 5, 2009As I understand it, the Physics ArXiv Blog is not affiliated with the people who actually run the Arxiv (Paul Ginsparg et al.). Which is probably good, as I'm never entirely sure how seriously to take the papers they highlight.
Take yesterday's post, Diamond Challenges for Quantum-Computing Crown, which is about a paper that asks the question Could one make a diamond-based quantum computer?. It's an interesting idea, and something I wrote about last year, so it seems like a promising topic.
The preprint in question, though, is a little dodgy. It's indifferently proofread, with all sorts of…
drorzel | April 16, 2009Physics World has a nice news article about a new experimental development in quantum computing, based on a forthcoming paper from the Wineland group at NIST in Boulder. I'd write this up for ResearchBlogging, but it's still just on the arxiv, and I don't think they've started accepting arxiv papers yet.
The Physics World piece summarizes the key results nicely:
Now, Brad Blakestad and colleagues at the National Institute of Standards and Technology (NIST) in Boulder, Colorado have created a junction in an ion trap in which there is practically no heating. Constructed from laser-machined…
drorzel | March 16, 2009Scientific American has an article by David Albert and Rivka Galchen with the New Scientist-ish headline Was Einstein Wrong?: A Quantum Threat to Special Relativity and the sub-head "Entanglement, like many quantum effects, violates some of our deepest intuitions about the world. It may also undermine Einstein's special theory of relativity."
An alternate title for this post might be "Son Of Why I Won't Make It as a Philosopher," because I really don't know what to make of it. The authors make authoritative-sounding references to a bunch of papers I haven't read, but then they also drop in…
drorzel | March 11, 2009Most people's first exposure to the ideas of modern atomic physics comes through the Bohr model of hydrogen, which treats the atom as something like a little solar system, with the positively charged nucleus as the sun, and negatively charged electrons orbiting in well-defined circular orbits. It's a very compelling picture, and works well for hydrogen (provided you make a couple of really odd assumptions), but it's completely wrong on the details. Electrons do not move in well-defined orbits, but rather exists as fuzzy wavefunctions spread over the space near the nucleus.
It turns out,…
drorzel | March 5, 2009EurekAlert had a press release yesterday titled Quantum paradox directly observed -- a milestone in quantum mechanics, which sounds like it ought to be great. The actual release, though....
For one thing, the description of the actual experiment is so vague as to be completely useless. It's not easy to quote without copying the whole thing, but it's short, so go read it yourself. Do you have any idea what's going on?
Second, it doesn't provide a complete citation for the article-- it gives the title, authors, and journal, but not the relevant page and volume information, which you need in…
drorzel | February 25, 2009Over at Dot Physics, Rhett is taking another whack at photons. If you recall, the last time he did this wasn't too successful, and this round fares no better:
So back to the photon. In my original post I made the claim that the photoelectric effect is not a great experiment to show photons. Maybe that is not how it came off, but that is what I meant. The photoelectric effect can be explained quite well with the classical electromagnetic waves model and a quantum nature of matter. Of course there is a quantum nature to light as well.
I think the biggest problem with the photon is that the…
drorzel | January 22, 2009My graduate alma mater made some news this week, with a new quantum teleportation experiment in which they "teleport" the state of one ytterbium ion to another ytterbium ion about a meter away. That may not sound like much, but it's the first time anybody has done this with ions in two completely separate traps, in different vacuum systems. It's also written up in Physics World, though they spell Chris Monroe's name wrong throughout.
The paper is coming out in Science, and I may try to write it up for a ResearchBlogging post over the weekend. I may also need to add it to the quantum…
drorzel | January 12, 2009 There's been a fair bit of press for the article Subtracting photons from arbitrary light fields: experimental test of coherent state invariance by single-photon annihilation, published last month in the New Journal of Physics, much of it in roughly the same form as the news story in Physics World (which is published by the same organization that runs the journal), which leads with:
A property of laser light first predicted in 1963 by the future Nobel laureate Roy Glauber has been verified by physicists in Italy.
These stories can be a little puzzling, though. After all, Glauber got his…
drorzel | January 8, 2009Over at the theoretical physics beach party, Moshe is talking about teaching quantum mechanics, specifically an elective course for upper-level undergraduates. He's looking for some suggestions of special topics:
The course it titled "Applications of quantum mechanics", and is covering the second half of the text by David Griffiths, whose textbooks I find to be uniformly excellent. A more accurate description of the material would be approximation methods for solving the Schrodinger equation. Not uncommonly in the physics curriculum, when the math becomes more demanding the physics tends to…
drorzel | December 19, 2008When I saw ZapperZ's post about this paper (arxiv version, expensive journal version) from the group of Serge Haroche in Paris, I thought it might be something I would need to incorporate into Chapter 5 of the book-in-progress. Happily, it's much too technical to require extensive re-writing. Having taken the time to read it, though, I might as well make a ResearchBlogging post of it... (My comments will be based on the arxiv version, because it's freely downloadable.)
So, "Freezing Coherent Field Growth in a Cavity by the Quantum Zeno Effect." That's quite a mouthful. What does it really…
drorzel | December 1, 2008I got email last week from the Institute of Physics pointing me to a pair of video interviews with Anton Zeilinger of the University of Vienna. Zeilinger has built an impressive career out of doing fundamental tests of quantum mechanics-- he's not only got the accent and the hair to be a brilliant physicist, he's got a long list of amazing experimental papers to back it up.
They've gone the Locus route, and not included any of the questions he was responding to, which is always a little weird. Zeilinger provides enough context that everything makes sense, though, and he says some really…
drorzel | November 13, 2008Over at Dot Physics, Rhett has just completed a two-part post (Part I, Part II) on quantum physics arguing against the use of photons in teaching quantum physics. Part I gives a very nice introduction to quantum physics, which is why I linked it, but Part II goes a little off the rails. There's not as much physics content, and it ends with a list of phenomena that are able to be described by semi-classical models of light, leading up to a question:
So, if there are no photons, why are they in all the textbooks? That is a great question. I am glad I asked it. I really don't have a great answer…
drorzel | October 29, 2008Last week, I wrote about ion traps as a possible quantum computing platform, which are probably the best established of the candidate technologies. This week, I'll talk about something more speculative, but closer to my own areas of research: neutral atoms in optical lattices.
This is a newer area, which pretty much starts with a proposal in 1999. There are a bunch of different variants of the idea, and what follows will be pretty general.
What's the system? Optical lattices use the interaction between atoms and a standing wave of light to produce a periodic array of wells in which individual…
drorzel | October 23, 2008Doug Natelson is thinking about fortuitous physics, inspired by some solid state examples:
Every now and then you stumble across a piece of physics, some detail about how the universe works, that is extremely lucky in some sense. For example, it's very convenient that Si is a great semiconductor, and at the same time SiO2 is an incredibly good insulator - in terms of the electric field that it can sustain before breakdown, SiO2 is about as good as it gets.
From my own field of physics, I would suggest the rubidium atom. Rubidium isn't a substance you run across every day, and that's a Good…
drorzel | October 22, 2008Some time back, I wrote about what you need to make a quantum computer. Given that it's election season, I thought I'd revisit the topic by looking in detail at the candidate technologies for quantum computing.
The first up is Ion Trap Quantum Computing, probably the most well-established of any of the candidates. The field really starts with Dave Wineland's group at NIST, though there is outstanding stuff being done by Chris Monroe at Maryland, and a host of others.
So, how do they stack up? Here are the facts about ion traps as a quantum computing system:
What's the system? Ion traps are,…
drorzel | October 16, 2008One of the annoying things about trying to explain quantum mechanics to a general audience is that the weirdness of the theory forces you to use incredibly convoluted examples. Pop-science books about quantum physics are full of schemes that the producers of the Saw movies would reject as implausibly complicated.
I wish I was posting to say that I had found a way around this, but I haven't. So here's another entry in the thriller-movie school of quantum analogies.
Imagine that you and a friend are out hiking, and find yourselves kidnapped by a sinister conspiracy of some sort. You're taken to…
drorzel | September 19, 2008The Pontiff beat me to it, but my Ph.D. alma mater has scored a $12.5 million grant from the NSF to fund the Joint Quantum Institute as a Physics Frontier Center for the development of quantum technology:
The Physics Frontier Center (PFC) award, effective September 1, will fund 17 graduate students, seven postdoctoral scientists and seven undergraduates as well as an extensive and highly cross-disciplinary research program under the general title Processing Quantum Coherence. Ultimately the work may lead to development of a computer that exploits the strange phenomena of quantum mechanics…