Goldstone and Higgs modes of photons inside a cavity
Abstract
Goldstone and Higgs modes have been detected in various condensed matter, cold atom and particle physics experiments. Here, we demonstrate that the two modes can also be observed in optical systems with only a few (artificial) atoms inside a cavity. We establish this connection by studying the $ U(1)/Z_2 $ Dicke model where $ N $ qubits (atoms) coupled to a single photon mode. We determine the Goldstone and Higgs modes inside the superradiant phase and their corresponding spectral weights by performing both $ 1/J=2/N $ expansion and exact diagonization (ED) study at a finite $ N $. We find nearly perfect agreements between the results achieved by the two approaches when $ N $ gets down even to $ N = 2 $. The quantum finite size effects at a few qubits make the two modes quite robust against an effectively small counterrotating wave term. We present a few schemes to reduce the critical coupling strength, so the two modes can be observed in several experimental systems of (artificial) atoms inside a cavity by just conventional optical measurements.
 Publication:

arXiv eprints
 Pub Date:
 December 2013
 arXiv:
 arXiv:1312.3404
 Bibcode:
 2013arXiv1312.3404Y
 Keywords:

 Quantum Physics;
 Condensed Matter  Strongly Correlated Electrons;
 Physics  Atomic Physics;
 Physics  Optics
 EPrint:
 8 pages, 5 figures