We present a quantum mechanical description of parametric down-conversion and phase-matching of Bloch-waves in non-linear photonic crystals. We discuss the theory in one-dimensional Bragg structures giving a recipe for calculating the down-converted emission strength and direction. We exemplify the discussion by making explicit analytical predictions for the emission amplitude and direction from a one-dimensional structure that consists of alternating layers of Al0.4Ga0.6As and Air. We show that the emission is suitable for the extraction of polarization-entangled photons.
Using only linear optical elements, the creation of dual-rail photonic entangled states is inherently probabilistic. Known entanglement generation schemes have low success probabilities, requiring large-scale multiplexing to achieve near-deterministi
c operation of quantum information processing protocols. In this paper, we introduce multiple techniques and methods to generate photonic entangled states with high probability, which have the potential to reduce the footprint of Linear Optical Quantum Computing (LOQC) architectures drastically. Most notably, we are showing how to improve Bell state preparation from four single photons to up to p=2/3, boost Type-I fusion to 75% with a dual-rail Bell state ancilla and improve Type-II fusion beyond the limits of Bell state discrimination.
We report the generation of polarization-entangled photons by femtosecond-pulse-pumped spontaneous parametric down-conversion in a cascade of two type-I crystals. Highly entangled pulsed states were obtained by introducing a temporal delay between th
e two orthogonal polarization components of the pump field. They exhibited high-visibility quantum interference and a large concurrence value, without the need of post-selection using narrow-bandwidth-spectral filters. The results are well explained by the theory which incorporates the space-time dependence of interfering two-photon amplitudes if dispersion and birefringence in the crystals are appropriately taken into account. Such a pulsed entangled photon well localized in time domain is useful for various quantum communication experiments, such as quantum cryptography and quantum teleportation.
We present a scheme to generate entangled photons using the NV centers in diamond. We show how the long-lived nuclear spin in diamond can mediate entanglement between multiple photons thereby increasing the length of entangled photon string. With the
proposed scheme one could generate both n-photon GHZ and cluster states. We present an experimental scheme realizing the same and estimating the rate of entanglement generation both in the presence and absence of a cavity.
We demonstrate experimentally that spontaneous parametric down-conversion in an AlGaAs semiconductor Bragg reflection waveguide can make for paired photons highly entangled in the polarization degree of freedom at the telecommunication wavelength of
1550 nm. The pairs of photons show visibility higher than 90% in several polarization bases and violate a Clauser-Horne-Shimony-Holt Bell-like inequality by more than 3 standard deviations. This represents a significant step toward the realization of efficient and versatile self pumped sources of entangled photon pairs on-chip.
Quantum blockade and entanglement play important roles in quantum information and quantum communication as quantum blockade is an effective mechanism to generate single photons (phonons) and entanglement is a crucial resource for quantum information
processing. In this work, we propose a method to generate single entangled photon-phonon pairs in a hybrid optomechanical system. We show that photon blockade, phonon blockade, and photon-phonon correlation and entanglement can be observed via the atom-photon-phonon (tripartite) interaction, under the resonant atomic driving. The correlated and entangled single photons and single phonons, i.e., single entangled photon-phonon pairs, can be generated in both the weak and strong tripartite interaction regimes. Our results may have important applications in the development of highly complex quantum networks.
William T.M. Irvine
,Michiel J.A. de Dood
,Dirk Bouwmeester
.
(2005)
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"Bloch theory of entangled photon generation in non-linear photonic crystals"
.
William Irvine
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