19 research outputs found
Phase-space interference in extensive and non-extensive quantum heat engines
Quantum interference is at the heart of what sets the quantum and classical
worlds apart. We demonstrate that quantum interference effects involving a
many-body working medium is responsible for genuinely non-classical features in
the performance of a quantum heat engine. The features with which quantum
interference manifests itself in the work output of the engine depends strongly
on the extensive nature of the working medium. While identifying the class of
work substances that optimize the performance of the engine, our results shed
light on the optimal size of such media of quantum workers to maximize the work
output and efficiency of quantum energy machines
A quantum heat engine with coupled superconducting resonators
We propose a quantum heat engine composed of two superconducting transmission
line resonators interacting with each other via an optomechanical-like
coupling. One resonator is periodically excited by a thermal pump. The
incoherently driven resonator induces coherent oscillations in the other one
due to the coupling. A limit cycle, indicating finite power output, emerges in
the thermodynamical phase space. The system implements an all-electrical analog
of a photonic piston. Instead of mechanical motion, the power output is
obtained as a coherent electrical charging in our case. We explore the
differences between the quantum and classical descriptions of our system by
solving the quantum master equation and classical Langevin equations.
Specifically, we calculate the mean number of excitations, second-order
coherence, as well as the entropy, temperature, power and mean energy to reveal
the signatures of quantum behavior in the statistical and thermodynamic
properties of the system. We find evidence of a quantum enhancement in the
power output of the engine at low temperatures.Comment: 15 pages, 14 figures, new references adde
Spin squeezing, entanglement and coherence in two driven, dissipative, nonlinear cavities coupled with single and two-photon exchange
We investigate spin squeezing, quantum entanglement and second order
coherence in two coupled, driven, dissipative, nonlinear cavities. We compare
these quantum statistical properties for the cavities coupled with either
single or two-photon exchange. Solving the quantum optical master equation of
the system numerically in the steady state, we calculate the zero-time delay
second-order correlation function for the coherence, genuine two-mode
entanglement parameter, and an optimal spin squeezing inequality associated
with particle entanglement. We identify regimes of distinct quantum statistical
character depending on the relative strength of photon-exchange and
nonlinearity. Moreover, we examine the effects of weak and strong drives on
these quantum statistical regimes.Comment: Improved version; new figures and discussion