68 research outputs found
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
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
Bright solitons in non-equilibrium coherent quantum matter
We theoretically demonstrate a mechanism for bright soliton generation in
spinor non-equilibrium Bose-Einstein condensates made of atoms or
quasiparticles such as polaritons in semiconductor microcavities. We give
analytical expressions for bright (half) solitons as minimizing functions of a
generalized non-conservative Lagrangian elucidating the unique features of
inter and intra-competition in non-equilibrium systems. The analytical results
are supported by a detailed numerical analysis that further shows the rich
soliton dynamics inferred by their instability and mutual cross-interactions.Comment: Published 13 January 2016 in Proc. Roy. Soc. A, DOI:
10.1098/rspa.2015.059
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
Separation and acceleration of analogues of magnetic monopoles in semiconductor microcavities
Half-integer topological defects in polariton condensates can be regarded as
magnetic charges, with respect to built-in effective magnetic fields present in
microcavities. We show how an integer topological defect can be separated into
a pair of half-integer ones, paving the way towards flows of magnetic charges:
spin currents or magnetricity. We discuss the corresponding experimental
implementation within microwires (with half-solitons) and planar microcavities
(with half-vortices).Comment: 18 Pages, 8 figures, submitted to New Journal of Physics (special
issue
An all-silicon single-photon source by unconventional photon blockade
The lack of suitable quantum emitters in silicon and silicon-based materials
has prevented the realization of room temperature, compact, stable, and
integrated sources of single photons in a scalable on-chip architecture, so
far. Current approaches rely on exploiting the enhanced optical nonlinearity of
silicon through light confinement or slow-light propagation, and are based on
parametric processes that typically require substantial input energy and
spatial footprint to reach a reasonable output yield. Here we propose an
alternative all-silicon device that employs a different paradigm, namely the
interplay between quantum interference and the third-order intrinsic
nonlinearity in a system of two coupled optical cavities. This unconventional
photon blockade allows to produce antibunched radiation at extremely low input
powers. We demonstrate a reliable protocol to operate this mechanism under
pulsed optical excitation, as required for device applications, thus
implementing a true single-photon source. We finally propose a state-of-art
implementation in a standard silicon-based photonic crystal integrated circuit
that outperforms existing parametric devices either in input power or footprint
area.Comment: 5 pages, 3 figures + Supplementary information (3 pages, 2 figures
Landau versus Spin Superfluidity in Spinor Bose-Einstein Condensates
We consider a spin-1/2 Bose-Einstein condensate prepared initially in a
single spin projection. The two channels of excitations existing in such a
system (namely density and spin waves) are discussed and we show how pure spin
waves can be excited in the presence of local magnetic defects. We analyze the
role played by spin excitations on the Landau superfluidity criterion and
demonstrate the absence of absolute superfluidity for the antiferromagnetic
condensate. In the ferromagnetic case, we identify two critical velocities for
the breakdown of superfluidity.Comment: 5 pages, 3 figure
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