86,941 research outputs found
Decoherence-free subspace and disentanglement dynamics for two qubits in a common non-Markovian squeezed reservoir
We study the non-Markovian entanglement dynamics of two qubits in a common
squeezed bath. We see remarkable difference between the non-Markovian
entanglement dynamics with its Markovian counterpart. We show that a
non-Markovian decoherence free state is also decoherence free in the Markovian
regime, but all the Markovian decoherence free states are not necessarily
decoherence free in the non-Markovian domain. We extend our calculation from
squeezed vacuum bath to squeezed thermal bath, where we see the effect of
finite bath temperatures on the entanglement dynamics.Comment: To appear in Phys. Rev. A (8 pages
Non-Markovian waiting time distribution
Simulation methods based on stochastic realizations of state vector
evolutions are commonly used tools to solve open quantum system dynamics, both
in the Markovian and non-Markovian regime. Here, we address the question of
waiting time distribution (WTD) of quantum jumps for non-Markovian systems. We
generalize Markovian quantum trajectory methods in the sense of deriving an
exact analytical WTD for non-Markovian quantum dynamics and show explicitly how
to construct this distribution for certain commonly used quantum optical
systems.Comment: journal versio
Exact closed master equation for Gaussian non-Markovian dynamics
Non-Markovian master equations describe general open quantum systems when no
approximation is made. We provide the exact closed master equation for the
class of Gaussian, completely positive, trace preserving, non-Markovian
dynamics. This very general result allows to investigate a vast variety of
physical systems. We show that the master equation for non-Markovian quantum
Brownian motion is a particular case of our general result. Furthermore, we
derive the master equation unraveled by a non-Markovian, dissipative stochastic
Schr\"odinger equation, paving the way for the analysis of dissipative
non-Markovian collapse models
Non-Markovian dynamics of a nanomechanical resonator measured by a quantum point contact
We study the dynamics of a nanomechanical resonator (NMR) subject to a
measurement by a low transparency quantum point contact (QPC) or tunnel
junction in the non-Markovian domain. We derive the non-Markovian
number-resolved (conditional) and unconditional master equations valid to
second order in the tunneling Hamiltonian without making the rotating-wave
approximation and the Markovian approximation, generally made for systems in
quantum optics. Our non-Markovian master equation reduces, in appropriate
limits, to various Markovian versions of master equations in the literature. We
find considerable difference in dynamics between the non-Markovian cases and
its Markovian counterparts. We also calculate the time-dependent transport
current through the QPC which contains information about the measured NMR
system. We find an extra transient current term proportional to the expectation
value of the symmetrized product of the position and momentum operators of the
NMR. This extra current term, with a coefficient coming from the combination of
the imaginary parts of the QPC reservoir correlation functions, has a
substantial contribution to the total transient current in the non-Markovian
case, but was generally ignored in the studies of the same problem in the
literature. Considering the contribution of this extra term, we show that a
significantly qualitative and quantitative difference in the total transient
current between the non-Markovian and the Markovian wide-band-limit cases can
be observed. Thus, it may serve as a witness or signature of the non-Markovian
features in the coupled NMR-QPC system.Comment: Accepted for publication in Physical Review B (20 pages, 13 figures
General Non-Markovian structure of Gaussian Master and Stochastic Schr\"odinger Equations
General open quantum systems display memory features, their master equations
are non-Markovian. We show that the subclass of Gaussian non-Markovian open
system dynamics is tractable in a depth similar to the Markovian class. The
structure of master equations exhibits a transparent generalization of the
Lindblad structure. We find and parametrize the class of stochastic
Schr\"odinger equations that unravel a given master equation, such class was
before known for Markovian systems only. We show that particular non-Markovian
unravellings known in the literature are special cases of our class
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