Photon Emission Processes Near Superconducting Bodies
KTH/Nordita/SU seminar in Theoretical Physics [before December 2013]
Tuesday 18 December 2007
to 12:00 at
Bo-Sture Skagerstam (Trondheim)
As was already pointed out by E.M. Purcell in 1948, the rate of
spontaneous emission of atoms will be modified due to the presence of a
dielectric body. Spontaneous emission can be thought of as a physical
process, where the emission of a photon is stimulated by vacuum
fluctuations. The presence of a medium will change the properties of the
vacuum and, hence, also the rate for decay processes. This so called
Purcell effect has been one of several central topics in the field of
modern experimental cavity quantum electrodynamics.
In current investigations and engineering of nano-scale atom
microtraps, this issue is also of fundamental importance since such
spontaneous emission processes, due to hyperfine spin-flip transitions,
have a direct bearing on the stability of atom chips.
In the present talk, we give a brief introduction to some of these
issues in terms of photon emission due to a magnetic spin-flip
transition of a two-level atom in the vicinity of a dielectric body like
a normal conducting metal or a superconductor. In the analysis of this
physical system one has to address issues like the notion of a photon
propagating close to or in a dissipative medium. A simpler but analogues
problem is how to quantize a damped harmonic oscillator.
For temperatures below the critical temperature of a superconductor,
the corresponding spin-flip lifetime can be boosted by almost twenty
orders of magnitude as compared to the case of a normal conducting body!
This recent finding of ours has opened up the window for the design of
new superconductor based atom chips.