Quantum electrodynamic fluctuations of the macroscopic Josephson phase
Abstract
We study the equilibrium dynamics of the relative phase in a superconducting Josephson link taking into account the quantum fluctuations of the electromagnetic vacuum. The photons act as a superohmic heat bath on the relative Cooper pair number and thus, indirectly, on the macroscopic phase difference φ. This leads to an enhancement of the mean square < φ^{2}> that adds to the spread due to the Coulomb interaction carried by the longitudinal electromagnetic field. We also include the interaction with the electronic degrees of freedom due to quasiparticle tunneling, which couple to the phase and only indirectly to the particle number. The simultaneous inclusion of both the radiation field fluctuations and quasiparticle tunneling leads to a novel type of particlebath Hamiltonian in which the quantum particle couples through its position and momentum to two independent bosonic heat baths. We study the interplay between the two mechanisms in the present context and find interference contributions to the quantum fluctuations of the phase. We explore the observability of the QED effects discussed here.
 Publication:

Annals of Physics
 Pub Date:
 March 2004
 DOI:
 10.1016/j.aop.2003.08.014
 arXiv:
 arXiv:condmat/0308567
 Bibcode:
 2004AnPhy.310..127K
 Keywords:

 42.50.Lc;
 74.40.+k;
 74.50.+r;
 Quantum fluctuations quantum noise and quantum jumps;
 Fluctuations;
 Tunneling phenomena;
 point contacts weak links Josephson effects;
 Condensed Matter  Superconductivity
 EPrint:
 19 pages