724 research outputs found
The quantum optical Josephson interferometer
The interplay between coherent tunnel coupling and on-site interactions in
dissipation-free bosonic systems has lead to many spectacular observations,
ranging from the demonstration of number-phase uncertainty relation to quantum
phase transitions. To explore the effect of dissipation and coherent drive on
tunnel coupled interacting bosonic systems, we propose a device that is the
quantum optical analog of a Josephson interferometer. It consists of two
coherently driven linear optical cavities connected via a central cavity with a
single-photon nonlinearity. The Josephson-like oscillations in the light
emitted from the central cavity as a function of the phase difference between
two pumping fields can be suppressed by increasing the strength of the
nonlinear coupling. Remarkably, we find that in the limit of ultra-strong
interactions in the center-cavity, the coupled system maps on to an effective
Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling
strength. In the limit of a single nonlinear cavity coupled to two linear
waveguides, the degree of photon antibunching from the nonlinear cavity
provides an excellent measure of the transition to the nonlinear regime where
Josephson oscillations are suppressed.Comment: 9 pages, 7 figure
Electromechanical Quantum Simulators
Digital quantum simulators are among the most appealing applications of a
quantum computer. Here we propose a universal, scalable, and integrated quantum
computing platform based on tunable nonlinear electromechanical
nano-oscillators. It is shown that very high operational fidelities for single
and two qubits gates can be achieved in a minimal architecture, where qubits
are encoded in the anharmonic vibrational modes of mechanical nanoresonators,
whose effective coupling is mediated by virtual fluctuations of an intermediate
superconducting artificial atom. An effective scheme to induce large
single-phonon nonlinearities in nano-electromechanical devices is explicitly
discussed, thus opening the route to experimental investigation in this
direction. Finally, we explicitly show the very high fidelities that can be
reached for the digital quantum simulation of model Hamiltonians, by using
realistic experimental parameters in state-of-the art devices, and considering
the transverse field Ising model as a paradigmatic example.Comment: 14 pages, 8 figure
Criminal rehabilitation : the impact of religious programming
Copyright, Christian Association for Psychological Studies, Inc.
Reprinted with permission.In spite of their prevalence in correctional institutions, religious programs have been the subject of limited
independent assessment. The purpose of the current study was to examine the outcomes of the Kairos
Short Course, a Christian religious course offered to prison inmates that aims to engage participants in
examination and meditation on their experiences, as well as the fostering of skills such as forgiveness and
empathic responsiveness. A sample of 38 inmates (20 assigned to attend the Kairos Short Course and 18
serving as a waiting-list comparison) at a medium security prison participated in the evaluation and were
assessed prior to and following completion of the Course on measures of criminal thinking, empathy, self
reflection, treatment readiness, and forgiveness of self and others. No clear evidence of change on any of
these measures was found. These results are of interest in the context of the growing need for service
providers to demonstrate that their programs are evidence-based and contribute to the community safety
goals of most correctional agencies. It is concluded that such results should temper some of the more
enthusiastic claims of some providers of religious programs to prisoners that such programs are successful
in rehabilitating large numbers of offenders
The quantum optical Josephson interferometer
The interplay between coherent tunnel coupling and on-site interactions in
dissipation-free bosonic systems has lead to many spectacular observations,
ranging from the demonstration of number-phase uncertainty relation to quantum
phase transitions. To explore the effect of dissipation and coherent drive on
tunnel coupled interacting bosonic systems, we propose a device that is the
quantum optical analog of a Josephson interferometer. It consists of two
coherently driven linear optical cavities connected via a central cavity with a
single-photon nonlinearity. The Josephson-like oscillations in the light
emitted from the central cavity as a function of the phase difference between
two pumping fields can be suppressed by increasing the strength of the
nonlinear coupling. Remarkably, we find that in the limit of ultra-strong
interactions in the center-cavity, the coupled system maps on to an effective
Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling
strength. In the limit of a single nonlinear cavity coupled to two linear
waveguides, the degree of photon antibunching from the nonlinear cavity
provides an excellent measure of the transition to the nonlinear regime where
Josephson oscillations are suppressed.Comment: 9 pages, 7 figure
Signatures of the super fluid-insulator phase transition in laser driven dissipative nonlinear cavity arrays
We analyze the non-equilibrium dynamics of a gas of interacting photons in an
array of coupled dissipative nonlinear cavities driven by a pulsed external
coherent field. Using a mean-field approach, we show that the system exhibits a
phase transition from a Mott-insulator-like to a superfluid regime. For a given
single-photon nonlinearity, the critical value of the photon tunneling rate at
which the phase transition occurs increases with the increasing photon loss
rate. We checked the robustness of the transition by showing its insensitivity
to the initial state prepared by the the pulsed excitation. We find that the
second-order coherence of cavity emission can be used to determine the phase
diagram of an optical many-body system without the need for thermalization.Comment: 4 pages, 4 figure
Non-equilibrium delocalization-localization transition of photons in circuit QED
We show that photons in two tunnel-coupled microwave resonators each
containing a single superconduct- ing qubit undergo a sharp non-equilibrium
delocalization-localization (self-trapping) transition due to strong
photon-qubit coupling. We find that dissipation favors the self-trapped regime
and leads to the possibility of observing the transition as a function of time
without tuning any parameter of the system. Furthermore, we find that
self-trapping of photons in one of the resonators (spatial localization) forces
the qubit in the opposite resonator to remain in its initial state (energetic
localization). This allows for an easy experimental observation of the
transition by local read-out of the qubit state.Comment: 4 pages, 5 figure
Digital quantum simulators in a scalable architecture of hybrid spin-photon qubits
Resolving quantum many-body problems represents one of the greatest
challenges in physics and physical chemistry, due to the prohibitively large
computational resources that would be required by using classical computers. A
solution has been foreseen by directly simulating the time evolution through
sequences of quantum gates applied to arrays of qubits, i.e. by implementing a
digital quantum simulator. Superconducting circuits and resonators are emerging
as an extremely-promising platform for quantum computation architectures, but a
digital quantum simulator proposal that is straightforwardly scalable,
universal, and realizable with state-of-the-art technology is presently
lacking. Here we propose a viable scheme to implement a universal quantum
simulator with hybrid spin-photon qubits in an array of superconducting
resonators, which is intrinsically scalable and allows for local control. As
representative examples we consider the transverse-field Ising model, a spin-1
Hamiltonian, and the two-dimensional Hubbard model; for these, we numerically
simulate the scheme by including the main sources of decoherence. In addition,
we show how to circumvent the potentially harmful effects of inhomogeneous
broadening of the spin systems
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