67 research outputs found
Coupling quasi-phase matching: entanglement buildup in nonlinear waveguide arrays
Wavevector quasi-phase matching was devised in the 1960s as a way to boost
nonlinear interactions with efficient quantum noise squeezing as one
outstanding outcome. In the era of quantum technologies, we propose a new
coupling quasi-phase matching for efficient generation of multimode
downconverted quantum light in nonlinear waveguide arrays. We highlight this
technique achieving multimode quantum entanglement and Einstein-Podolsky-Rosen
steering buildup. We discuss the feasibility of this method with current
technology and demonstrate its competitiveness as a resource for continuous
variables quantum information.Comment: 9 pages, 5 figures, v2 closer to published versio
Zero supermode-based multipartite entanglement in nonlinear waveguides arrays
We show that arrays of nonlinear waveguides in the second
harmonic generation regime are a promising source of continuous-variable
entanglement. We indeed demonstrate analytically that optical arrays with odd
number of waveguides injected with the zero-eigenvalue fundamental supermode
entangle this fundamental supermode with a collective harmonic field. Moreover
the fundamental individual modes are multipartite entangled and their
entanglement grows with propagation length. The device is scalable, robust to
losses, does not rely on specific values of nonlinearity and coupling and is
easily realized with current technology. It thus stands as an unprecedented
candidate for generation of multipartite continuous-variable entanglement for
optical quantum information processing.Comment: Main text: 7 pages, 6 figures. Supplemental material: 5 pages, 2
figure. v2 closer to published versio
Exact results for nonequilibrium dynamics in Wigner phase space
We study time evolution of Wigner function of an initially interacting one-dimensional quantum gas following the switch-off of the interactions. For the scenario where at t=0the interactions are suddenly suppressed, we derive a relationship between the dynamical Wigner function and its initial value. A two-particle system initially interacting through two different interactions of Dirac delta type is examined. For a system of particles that is suddenly let to move ballistically (without interactions) in a harmonic trap in d dimensions, and using time evolution of one-body density matrix, we derive a relationship between the time dependent Wigner function and its initial value. Using the inverse Wigner transform we obtain, for an initially harmonically trapped noninteracting particles in ddimensions, the scaling law satisfied by the density matrix at time tafter a sudden change of the trapping frequency. Finally, the effects of interactions are analyzed in the dynamical Wigner function.Ministerio de EconomĂa, Industria y Competitividad (grant MTM2014-57129-C2-1-P)Junta de Castilla y LeĂłn (grants BU229P18, VA057U16, and VA137G18
Continuous-variable entanglement of two bright coherent states that never interacted
We study continuous-variable entanglement of bright quantum states in a pair
of evanescently coupled nonlinear waveguides operating in the
regime of degenerate down-conversion. We consider the case where only the
energy of the nonlinearly generated fields is exchanged between the waveguides
while the pump fields stay independently guided in each original waveguide. We
show that this device, when operated in the depletion regime, entangles the two
non-interacting bright pump modes due to a nonlinear cascade effect. It is also
shown that two-colour quadripartite entanglement can be produced when certain
system parameters are appropriately set. This device works in the
traveling-wave configuration, such that the generated quantum light shows a
broad spectrum. The proposed device can be easily realized with current
technology and therefore stands as a good candidate for a source of bipartite
or multipartite entangled states for the emerging field of optical
continuous-variable quantum information processing.Comment: 10 pages, 12 figure
Hierarchy of Genuine Tripartite Non-Gaussian Entanglement
Triple-photon states generated by three-mode spontaneous parametric
down-conversion are the paradigm of unconditional non-Gaussian states,
essential assets for quantum advantage. How to fully characterize their
non-Gaussian entanglement remains however elusive. We propose here a hierarchy
of sufficient and necessary conditions for separability of the broad family of
spontaneously-generated three-mode non-Gaussian states. We further derive
state-of-the-art conditions for genuine tripartite non-Gaussian entanglement,
the strongest class of entanglement. We apply our criteria to triple-photon
states revealing that they are fully inseparable and genuinely entangled in
moments of order 3n. Our results establish a systematic framework for
characterizing the entanglement of triple-photon states and thus fostering
their application in quantum information protocols
Symmetry-based analytical solutions to the \chi^{(2)} nonlinear directional coupler
In general the ubiquitous \chi^{(2)} nonlinear directional coupler, where
nonlinearity and evanescent coupling are intertwined, is nonintegrable. We
rigorously demonstrate that matching excitation to the even or odd fundamental
supermodes yields dynamical analytical solutions for any phase matching in a
symmetric coupler. We analyze second harmonic generation and optical parametric
amplification regimes and study the influence of fundamental fields parity and
power on the operation of the device. These fundamental solutions are useful to
develop applications in classical and quantum fields such as all-optical
modulation of light and quantum-states engineering.Comment: 7 pages, 6 figure
Minimum resources for versatile continuous variable entanglement in integrated nonlinear waveguides
In a recent paper [Phys. Rev. A {\bf 96}, 053822 (2017)], we proposed a
strategy to generate bipartite and quadripartite continuous-variable
entanglement of bright quantum states based on degenerate down-conversion in a
pair of evanescently coupled nonlinear waveguides. Here, we show
that the resources needed for obtaining these features can be optimized by
exploiting the regime of second harmonic generation: the combination of
depletion and coupling among pump beams indeed supplies all necessary
wavelengths and appropriate phase mismatch along propagation. Our device thus
entangles the two fundamental classical input fields without the participation
of any harmonic ancilla. Depending on the propagation distance, the generated
harmonics are entangled in bright or vacuum modes. We also evidence two-color
bipartite and quadripartite entanglement over the interacting modes. The
proposed device represents a boost in continuous-variable integrated quantum
optics since it enables a broad range of quantum effects in a very simple
scheme, which optimizes the resources and can be easily realized with current
technology.Comment: 8 pages, 8 figure
Microcavity-quality-factor enhancement using nonlinear effects close to the bistability threshold and coherent population oscillations
9 pagesInternational audienceWe analytically show that inserting a driven, two-level system inside a microcavity can improve its optical properties. In this approach, the strong dispersion induced by a pump via population oscillations increases the cavity lifetime experienced by a slightly detuned probe. We further predict that if the cavity is pumped through a resonant channel, optical absorptive or dispersive bistability can be combined with the population-oscillation-induced steep material dispersion to obtain a strong quality-factor enhancement. Moreover, differential amplification coming from the nonlinear feature of the pump transfer function can be used to drastically increase the probe transmission beyond intrinsic characteristics of the resonator. The Q-factor enhancement and the differential amplification can be advantageously combined with a frequency pulling effect to stabilize or readjust the microcavity resonance frequency
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