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.