Abstract: Various embodiments of the present invention are directed to compact systems for generating polarization-entangled photons. In one embodiment of the present invention, a polarization entangled-photon state source comprises a single transmission layer configured for transmitting electromagnetic radiation. The transmission layer includes a beamsplitter and a down-conversion device, both of which are configured to convert a pump beam into first and second signal beams and first and second idler beams. The transmission layer also includes a mode converter configured to invert electric and magnetic field components of both the first signal beam and the first idler beam, and a combiner configured to receive the first and second signal beams and the first and second idler beams and output the first and second signal beams and the first and second idler beams in an entangled polarization states.

Abstract: Various embodiments of the present invention are directed to compact systems for generating polarization-entangled photons. In one embodiment of the present invention, a polarization entangled-photon state source comprises a single transmission layer configured for transmitting electromagnetic radiation. The transmission layer includes a beamsplitter and a down-conversion device, both of which are configured to convert a pump beam into first and second signal beams and first and second idler beams. The transmission layer also includes a mode converter configured to invert electric and magnetic field components of both the first signal beam and the first idler beam, and a combiner configured to receive the first and second signal beams and the first and second idler beams and output the first and second signal beams and the first and second idler beams in an entangled polarization states.

Abstract: Various embodiments of the present invention are directed to color-center-based quantum computer architectures that are both scalable and defect tolerant and to methods for fabricating color-center-based quantum computer architectures. In one embodiment of the present invention, a node of a quantum computer architecture comprises a first photonic device configured to transmit electromagnetic waves, a color center embedded in diamond and coupled to the first photonic device, and a switch located between the first photonic device and a bus waveguide. The switch can be configured to selectively control transmission of electromagnetic waves between the bus waveguide and the color center.

Abstract: A source and/or method of generating quantum-correlated and/or entangled photon pairs using parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550 nm fiber-optic communication band and detected by a detection system including InGaAs/InP avalanche photodiodes operating in a gated Geiger mode. A generation rate>103 pairs/s is observed, a rate limited only by available detection electronics. The nonclassical nature of the photon correlations in the pairs is demonstrated. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks. The detection system also provides high rate of photon counting with negligible after pulsing and associated high quantum efficiency and also low dark count rate.