Wednesday, March 28, 2007

Gabrielse talk

This'll be my last talk description for a while, I promise. Colloquium today was Gerry Gabrielse, talking about their group's latest measurements of the g factor of the electron (really [g/2-1]) and the accompanying inferred value for the fine structure constant. Gabrielse did open his talk with most of this clip, since it's about their work. On a random note, I TAed the first author on that first paper once when he was an undergrad.

Precision measurement physics is extremely impressive in its own way. They measure g to parts in 10^13, and \alpha to parts in 10^10 by doing incredibly precise spectroscopy on a single trapped electron in a magnetic field. To really do this right, they have to get rid of all the relevant black body photons in the microwave range, meaning that they have to cool their cavity down to 80 mK. They also need to account for cavity QED effects - again it's a restricted density of states argument. They get the lifetime for spontaneous emission of a microwave photon from the first excited state to the ground state of their trapped electron to be 260 times what it would be in free space. They achieve this lifetime enhancement by making sure to operate their cavity such that there just aren't any cavity modes available at the right energy for the would-be photon to occupy. A tour de force piece of work. I'm pretty sure that precision measurement like this would drive me bonkers.

9 comments:

Aaron said...

I can just hear your thoughts while trying such an experiment, Doug.

"Do I really need that 13 significant figure? Is anyone really going to miss it? How much more effort is one measely digit worth anyways?"

Doug Natelson said...

...and I can hear your thoughts, Aaron. "If one more person slams the lab door while I'm trying to take this 13th significant digit, I'm going to smack them." :-)

hermanweyl said...

Doug,
I read your silly comment in FSP's blog directed towards me. My country won a nobel prize just last year. FYI...
Let me know when you get one. Please do some research next time before you write stupid things, ok?

Doug Natelson said...

Hermanweyl - I didn't make any such comment. Now that I've gone and read that thread, I understand your comment here. Please think before you write stupid things, ok?

And give me a little damned respect. Last time I checked, I had a PhD and tenure.

Dan M said...

So, unless your name is really hermanweyl (which I doubt, since he's dead), why are you flaming at people who post anonymously? Are you a black pot or a black kettle?

rudolfpeierls said...

Doug,
I am sorry... The guy in FSP's blog seems to replicate what you wrote here before so I assumed it was you. You have an impersonator on the web. I also hate being called names like jackass.
dan m, I am not Herman Weyl obviously but I did not start a blog claiming I am Herman Weyl either. You are not dan m either presumably, are you?
Is it ok if I call myself rudolf peierls?

Dan M said...

In fact Dan M is my real name - I'm not ashamed of what I post, so what's the problem with signing my posts?

However, I fail to see the significance of the distinction you have mentioned between blogging anonymously and posting comments anonymously. In fact, I see nothing wrong with anonymity at all. I do see something wrong with criticizing people for being anonymous, while declining to admit your own name. That makes you a hypocrite, as far as I'm concerned.

Rudolf Peierls is also dead, by the way.

stevenweinberg said...

dan m, I am sorry for picking dead people. I did not know it was a problem for you. I am steven weinberg from now on. I hope it is good enough for you. You cannot argue I am not him at least, right?

Anonymous said...

dude my names Aaron Gabrielse too:)