I’ve been looking at Chapters 6 and 11 of Prof. Happer’s Optically Pumped Atoms
Well, so it looks like I’ll be sticking with the devil I know: writing terms into my optical Bloch equations to model pressure broadening and excited state depolarization piece by piece … in physically (and least to me) intuitive terms.
Maybe one day I’ll understand Prof. Happer’s approach.
Griffiths says in the introduction to Elementary particle physics,
If you were dealing with two macroscopic objects, and you wanted to know how they interact, you would probably begin by holding them at various separation distances and measuring the force between them. That’s how Coulomb determined the law of electrical repulsion between two charged pith balls, and how Cavendish measured the gravitational attraction of two lead weights. But you can’t pick up a proton with tweezers or tie and electron onto the end of a piece of string; they’re just too small.
Well, I guess to be fair, we call it “optical tweezer” but it looks nothing like actual tweezers. But if you want superficial similarity tweezers, there’s always atomic force microscopy, which uses cantilevers that, fundamentally and materially, isn’t that different from tweezers or any other long, slender objects.
With the first programmable quantum computer realized the day may come when Shor’s algorithm can be implemented with some accuracy:
“A team at NIST (the National Institute of Standards and Technology) used berylium ions, lasers and electrodes to develop a quantum system that performed 160 randomly chosen routines. Other quantum systems to date have only been able to perform single, prescribed tasks. Other researchers say the system could be scaled up. ‘The researchers ran each program 900 times. On average, the quantum computer operated accurately 79 percent of the time, the team reported in their paper.’”
I might be alone in this, but I fear the day when quantum computers become practical—much more than the day when the Singularity emerges; I have at least a sense of anticipation for the latter and it will represent a progress, an evolution of sorts. In contrast, all the uses for a quantum computer I know are evil—just like the atomic bomb and the hydrogen bomb. There is never a peaceful reason to enrich uranium more than 10%, and there is never a moral reason for a quantum computer to work more than 1% (or some other low number) of the time.
Will some other breakthrough make encryption—specifically, cheap and affordable encryption; for the wealthy and powerful, there is always OTP—available to the masses again, once quantum computers inevitably make public key encryptions (SSL and PGP, for the two big ones in use widely today) unusable except as children’s playthings?
Now, Klaus Hornberger of Ludwig-Maximilians University in Munich and his postdoc Johannes Trost have resolved Hund’s venerable paradox.1 The two theoreticians analyzed the case of one of the smallest chiral molecules, dideuterium disulfide (D2S2; see figure 1), tumbling in and buffeted by a monatomic gas, helium. The calculation uncovered a surprisingly large phase dependence in the scattering amplitude that distinguishes the two isomers. Thanks to the phase dependence, the ambient gas atoms can pick out the molecule’s left-handed and right-handed isomers far more readily than the molecule’s other states. Even at low temperature and pressure, the effect of the He atoms colliding again and again with D2S2 is to knock the molecule into a chiral state and keep it there before it has a chance to tunnel out to its mirror image.
In one sense, Hornberger and Trost’s result is rather mundane: If you take proper, quantum account of how atoms collide with molecules, you derive the expected result, a mix of left-handed and right-handed isomers. But that mundanity is profound. The transition from a quantum superposition to a classical state arises not when some mysterious size threshold is breached but when the system’s interaction with its environment exceeds a calculable level of intensity. Decoherence theory, as that envirocentric view is known, is vindicated.
The decoherence theory of macroscopic and microscopic divide always appealed to me as an explanation of the quantum measurement problem (it boils down to saying that there is no fundamental problem), but … is this it?
Because of my damnable habit of falling asleep in lectures I couldn’t catch it all, but if I remember Prof. Commins’ description of the quantum measurement problem and its proposed solutions correctly, he had deep reservations about the decoherence theory (and he had a few examples to support his reservation which, again because of my habit of falling asleep in lectures, I didn’t catch).
Maybe I should drop by some time and ask him.
Or next generation of re-wording what others have been doing for almost a decade?
By using a laser beam to impose the quantum state of a molecular transistor, the research team demonstrated control of a second laser beam, which reflects the way in which a conventional transistor works.
“The next step is to ‘connect’ two or more [single-molecule optical transistors],” Pototschnig told us with regard to future areas the team will be focusing on. “In other words, we have to connect two molecules in a way that the quantum mechanical superposition state of each molecule is exchanged in a coherent manner. Only that way the strength of the quantum computing principles can be fully taken advantage of. We are in the middle of coming up with actual ways to implement the connection idea.”
I fail to see how this is different from normal and usual techniques (such as CPT and EIT, which involves two lasers (or more) acting coherently on three (or more) atomic levels) people have been using in AMO physics for a very long time. And I think at least for two decades or so (i.e. since the advent of laser cooling), people have been doing this stuff with single atoms (and maybe single molecules) in a cavity.
I mean, it’s one thing for some people to call these devices “optical switch”, in order to bring attention to the fact that, well, these effects can be used as optical switch (networks and communications people wouldn’t be as enthralled with words like “electromagnetically induced transparency” or “coherent population trapping”). But to claim that something that is little more than an optical switch is actually a “optical transistor”? That seems, well, irresponsible.
It’s a shame that this article didn’t actually link to the journal article supposedly published in Nature. Then I could see for myself whether this is yet another typical bad science journalism (for every good article I see in science and tech, I see at least 2 or 3 spectacularly bad ones), or if the author himself is, well, so isolated from the scientific community that he doesn’t know that he is simply reproducing what others have been doing for a long time—except, I guess, that he’s using a slightly more complicated molecule, maybe.
Edit: This article links to the journal in the references (found via Slashdot comments). You’ll need some kind of library subscription to see full article, but even the abstract shows that the authors of this article did consider other work in AMO physics using cooled/trapped atoms in cavities, and their work, presumably, represents a marginal advancement in these techniques. So, this is yet another case of bad, sensationalist journalism, where the so-called “journalist” tries to justify his salary by trying to paint a small-step improvement as some kind of other-worldly breakthrough (… that he happens to be covering).
Wee!
I have to admit … it’s not quite breathtaking as some of the more brilliant student research (such as the one involving entangled photons—it received some “Nobel prize of undergraduate research” award and was also featured in APS newsletter), but it’s my first publication.
Well, first publication in college. With me as an author, not a technical editor.
And it couldn’t have come at a better time, since I need to be finishing off my college applications. 