4,821 research outputs found
Degree of Quantumness in Quantum Synchronization
We introduce the concept of degree of quantumness in quantum synchronization,
a measure of the quantum nature of synchronization in quantum systems.
Following techniques from quantum information, we propose the number of
non-commuting observables that synchronize as a measure of quantumness. This
figure of merit is compatible with already existing synchronization
measurements, and it captures different physical properties. We illustrate it
in a quantum system consisting of two weakly interacting cavity-qubit systems,
which are coupled via the exchange of bosonic excitations between the cavities.
Moreover, we study the synchronization of the expectation values of the Pauli
operators and we propose a feasible superconducting circuit setup. Finally, we
discuss the degree of quantumness in the synchronization between two quantum
van der Pol oscillators
Synchronization, quantum correlations and entanglement in oscillator networks
Synchronization is one of the paradigmatic phenomena in the study of complex
systems. It has been explored theoretically and experimentally mostly to
understand natural phenomena, but also in view of technological applications.
Although several mechanisms and conditions for synchronous behavior in
spatially extended systems and networks have been identified, the emergence of
this phenomenon has been largely unexplored in quantum systems until very
recently. Here we discuss synchronization in quantum networks of different
harmonic oscillators relaxing towards a stationary state, being essential the
form of dissipation. By local tuning of one of the oscillators, we establish
the conditions for synchronous dynamics, in the whole network or in a motif.
Beyond the classical regime we show that synchronization between (even
unlinked) nodes witnesses the presence of quantum correlations and
entanglement. Furthermore, synchronization and entanglement can be induced
between two different oscillators if properly linked to a random network.Comment: 10 pages, 5 figures, submitted to Scientific Report
Open system dynamics with non-Markovian quantum trajectories
A non-Markovian stochastic Schroedinger equation for a quantum system coupled
to an environment of harmonic oscillators is presented. Its solutions, when
averaged over the noise, reproduce the standard reduced density operator
without any approximation. We illustrate the power of this approach with
several examples, including exponentially decaying bath correlations and
extreme non-Markovian cases, where the `environment' consists of only a single
oscillator. The latter case shows the decay and revival of a `Schroedinger cat'
state. For strong coupling to a dissipative environment with memory, the
asymptotic state can be reached in a finite time. Our description of open
systems is compatible with different positions of the `Heisenberg cut' between
system and environment.Comment: 4 pages RevTeX, 3 figure
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