388 research outputs found
Heralded Preparation and Readout of Entangled Phonons in a Photonic Crystal Cavity
We propose a realistic protocol for the preparation and readout of mechanical
Bell states in an optomechanical system. The proposal relies on parameters
characterizing a photonic crystal cavity mode, coupled to two localized
flexural modes of the structure, but equally applies to other optomechanical
systems in the same parameter range. The nonclassical states are heralded via
optical postselection and revealed in specific interference patterns
characterizing the emission at the cavity frequency.Comment: 5 Pages, 3 Figures + Supplemental Material 3 Pages, 3 Figure
Input-output theory of the unconventional photon blockade
We study the unconventional photon blockade, recently proposed for a
coupled-cavity system, in presence of input and output quantum fields. Mixing
of the input or output channels still allows strong photon antibunching of the
output field, but for optimal values of the system parameters that differ
substantially from those that maximize antibunching of the intracavity field.
This result shows that the specific input-output geometry in a photonic system
determines the optimal design in view of single-photon device operation. We
provide a compact analytical formula that allows finding the optimal parameters
for each specific system geometry.Comment: 8 pages, 4 figure
Remote Macroscopic Entanglement on a Photonic Crystal Architecture
The outstanding progress in nanostructure fabrication and cooling
technologies allows what was unthinkable a few decades ago: bringing
single-mode mechanical vibrations to the quantum regime. The coupling between
photon and phonon excitations is a natural source of nonclassical states of
light and mechanical vibrations, and its study within the field of cavity
optomechanics is developing lightning-fast. Photonic crystal cavities are
highly integrable architectures that have demonstrated the strongest
optomechanical coupling to date, and should therefore play a central role for
such hybrid quantum state engineering. In this context, we propose a realistic
heralding protocol for the on-chip preparation of remotely entangled mechanical
states, relying on the state-of-the-art optomechanical parameters of a
silicon-based nanobeam structure. Pulsed sideband excitation of a Stokes
process, combined with single photon detection, allows writing a delocalised
mechanical Bell state in the system, signatures of which can then be read out
in the optical field. A measure of entanglement in this protocol is provided by
the visibility of a characteristic quantum interference pattern in the emitted
light.Comment: 8 pages, 5 Figure
Quantum Entanglement in Nanocavity Arrays
We show theoretically how quantum interference between linearly coupled modes
with weak local nonlinearity allows the generation of continuous variable
entanglement. By solving the quantum master equation for the density matrix, we
show how the entanglement survives realistic levels of pure dephasing. The
generation mechanism forms a new paradigm for entanglement generation in arrays
of coupled quantum modes.Comment: 5 pages, 3 figure
Single photons from coupled quantum modes
Single photon emitters often rely on a strong nonlinearity to make the
behaviour of a quantum mode susceptible to a change in the number of quanta
between one and two. In most systems the strength of nonlinearity is weak, such
that changes at the single quantum level have little effect. Here, we consider
coupled quantum modes and and that they can be strongly sensitive at the single
quantum level, even if nonlinear interactions are modest. As examples, we
consider solid-state implementations based on the tunneling of polaritons
between quantum boxes or their parametric modes in a microcavity. We find that
these systems can act as promising single photon emitters.Comment: 4 pages, 3 figure
Optimal antibunching in passive photonic devices based on coupled nonlinear resonators
We propose the use of weakly nonlinear passive materials for prospective
applications in integrated quantum photonics. It is shown that strong
enhancement of native optical nonlinearities by electromagnetic field
confinement in photonic crystal resonators can lead to single-photon generation
only exploiting the quantum interference of two coupled modes and the effect of
photon blockade under resonant coherent driving. For realistic system
parameters in state of the art microcavities, the efficiency of such
single-photon source is theoretically characterized by means of the
second-order correlation function at zero time delay as the main figure of
merit, where major sources of loss and decoherence are taken into account
within a standard master equation treatment. These results could stimulate the
realization of integrated quantum photonic devices based on non-resonant
material media, fully integrable with current semiconductor technology and
matching the relevant telecom band operational wavelengths, as an alternative
to single-photon nonlinear devices based on cavity-QED with artificial atoms or
single atomic-like emitters.Comment: to appear in New J. Physic
Optically erasing disorder in semiconductor microcavities with dynamic nuclear polarization
The mean squared value of the photonic disorder is found to be reduced by a
factor of 100 in a typical GaAs based microcavity, when exposed to a circularly
polarized continuous wave optical pump without any special spatial patterning.
Resonant excitation of the cavity mode excites a spatially non-uniform
distribution of spin-polarized electrons, which depends on the photonic
disorder profile. Electrons transfer spin to nuclei via the hyperfine contact
interaction, inducing a long-living Overhauser magnetic field able to modify
the potential of exciton-polaritons.Comment: 4 pages, 3 figure
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