## Tuesday, October 04, 2005 ... /////

### Half of Nobel "stays" at Harvard

The 2005 physics Nobel prize has been divided between three people. One of them who wins half a prize - Roy Glauber - is our colleague at Harvard. Congratulations! He already has a lot of experience with the Nobel prizes (sorry but it's just difficult for me to get the voice out of my nose!); see the first photograph here. (Also, he grew up in the same apartment building as the Kadanoffs and a block away from Sheldon Glashow.)

The press conference started at 11:00 am here in the physics library at Harvard; the reception began at 4:00 pm in the same library. John Huth and others said some entertaining and nice stories about Roy, who spoke himself, much like dean Kirby and Larry Summers. After some wise Jewish proverbs and other nice words, Larry also admitted that while he was the secretary of treasury under Clinton, he made the Nobel prize taxable! :-) Of course that he would have avoided the mistake if he knew about the award today. This was the tenth physics Nobel prize for Harvard - and the winners number #11-#15 were probably in the room already. :-)

Roy Glauber was born in 1925, more or less much like quantum mechanics, and you can guess that it is no coincidence. Although his name does not occur too often in textbooks, his contributions are very important. Especially the contributions to detailed balance (his special stochastic matrices that satisfy it) and quantum optical coherence for which he was awarded. See some of his other articles at Google.

The fact that absolutely no one has figured out that the winners could be candidates - not even The Reference Frame - does not mean that they don't deserve it!

What do I mean? Consider the Hilbert space for the harmonic oscillator. You often write down the state |0> (thanks to Quantoken for telling me that every child remembers that the vertical line is written as "ampersand hashmark seven c semicolon"), but you may also want to consider the "coherent" states |z> that are the eigenstates of the annihilation operator "a":

• a|z> = z|z>
In the phase space, this coherent state |z> looks just like the ground state, but it is shifted by some amount both in the position and the momentum directions. Glauber studied these states in various contexts that are described by the harmonic oscillator - which includes the electromagnetic field itself as well as other fields. He understood that this very right combination of states with different numbers of particles - one that can also be written as "exp(z a+)|0>" - has the effect of shifting the classical value.

All of us use these fundamental insights in quantum mechanics, including string theory. In string theory, the coherent states are used, among many other things, to explain that all vacua in the same moduli space may be obtained from each other and lead to an equivalent theory. There is only one string theory although it has many states in its Hilbert space.

Glauber also figured out some essential features of the squeezed states and other states. This text is not supposed to cover everything he did.

The other half

The other half of the Nobel prize is divided to John Hall from Boulder, Colorado, and Theodor Hänsch from Munich, Germany for their work on laser-based precision spectroscopy, including the optical frequency comb technique which was - unlike the coherent states - discovered very recently. It involves femtosecond lasers. It may be the first time I hear the names of the two Gentlemen, and it may be better to leave qualified comments to some atomic/molecular/optical physics bloggers (thanks to Dave - I really did not mean condensed matter physics) if one exists.

The "comb" of course means that an equally spaced set of frequencies can be localized using the laser; this technology allows one to improve the measurements of length by three orders of magnitude, among other things.

You can see that the fraction of the Nobel prizes going to the U.S. still safely exceeds the proportion of the carbon dioxide created in the same country. Also, in this particular competition, it is not Princeton that competes with Harvard: it's Stanford. Harvard will actually have to receive a few more physics Nobel prizes to catch up with Stanford.

#### snail feedback (5) :

You need to be more consistent with the name: Glauber (not Grauber).

Dear Wolfgang,

should not you have simply said that there was one typo in the article? Is it appropriate to talk about "consistency"?

Unlike you, I view the names Grauber and Glauber as almost identical. Glauben probably means to think, does not it? Grauben is to steal, or something else? ;-)

Best
Lubosch

Lubos:
Why do you need to spend one hour to figure out how to write the vertical slasp |? It's an ASCII character of value 0x7c, so you can simply use &#x7c.

Quantoken