23 research outputs found
Dynamics, correlations and phases of the micromaser
The micromaser possesses a variety of dynamical phase transitions
parametrized by the flux of atoms and the time-of-flight of the atom within the
cavity. We discuss how these phases may be revealed to an observer outside the
cavity using the long-time correlation length in the atomic beam. Some of the
phase transitions are not reflected in the average excitation level of the
outgoing atom, which is the commonly used observable. The correlation length is
directly related to the leading eigenvalue of the time evolution operator,
which we study in order to elucidate the phase structure. We find that as a
function of the time-of-flight the transition from the thermal to the maser
phase is characterized by a sharp peak in the correlation length. For longer
times-of-flight there is a transition to a phase where the correlation length
grows exponentially with the flux. We present a detailed numerical and
analytical treatment of the different phases and discuss the physics behind
them.Comment: 60 pages, 18 figure files, Latex + \special{} for the figures, (some
redundant figures are eliminated and others are changed
Landau-Zener-StĂĽckelberg-Majorana lasing in circuit quantum electrodynamics
We demonstrate amplification (and attenuation) of a probe signal by a driven
two-level quantum system in the Landau-Zener-St\"{u}ckelberg-Majorana regime by
means of an experiment, in which a superconducting qubit was strongly coupled
to a microwave cavity, in a conventional arrangement of circuit quantum
electrodynamics. Two different types of flux qubit, specifically a conventional
Josephson junctions qubit and a phase-slip qubit, show similar results, namely,
lasing at the working points where amplification takes place. The experimental
data are explained by the interaction of the probe signal with Rabi-like
oscillations. The latter are created by constructive interference of
Landau-Zener-St\"{u}ckelberg-Majorana (LZSM) transitions during the driving
period of the qubit. A detailed description of the occurrence of these
oscillations and a comparison of obtained data with both analytic and numerical
calculations are given