An apparatus is disclosed herein. The apparatus comprises a non-linear photonic element for outputting a signal and idler photon pair. The apparatus further comprises a module configured to, based on receiving one or more control signals, controllably store photons and controllably output stored photons. The apparatus further comprises a detector arrangement comprising one or more detectors for detecting light. The module is further configured to receive at least one of the signal and idler photons of the pair. The module is further configured to at least partially store one of the signal or idler photons of the pair. The module is further configured to output the said at least partially stored signal or idler photon along an optical path towards the at least one detectors. The apparatus is configured to direct the other of the signal or idler photon towards the detector arrangement.

A system for generating clock signals for a photonic quantum computing system includes a pump photon source configured to generate a plurality of pump photon pulses at a first repetition rate, a waveguide optically coupled to the pump photon source, and a photon-pair source optically coupled to the first waveguide. The system also includes a photodetector optically coupled to the photon-pair source and configured to generate a plurality of electrical pulses in response to detection of at least a portion of the plurality of pump photon pulses at the first repetition rate and a clock generator coupled to the photodetector and configured to convert the plurality of electrical pulses into a plurality of clock signals at the first repetition rate.

An optical ring resonator that includes a closed loop core, a cladding layer, and one or more bus waveguides. The closed loop core is disposed in the cladding layer and is As.sub.2Se.sub.3 glass. The one or more bus waveguides are disposed in the cladding layer and are optically coupled to the closed loop core. The closed loop core has a zero-dispersion wavelength within a telecommunication wavelength band. The closed loop core has a plurality of resonant modes, including a zero-dispersion resonant mode corresponding with the zero-dispersion wavelength and a plurality of paired resonant modes. Further, the closed loop core has a phase matching bandwidth extending greater than ±40 nm from the zero-dispersion wavelength.

Aspects of the present disclosure are directed to photon-pair sources based on an external-cavity laser comprising a gain element and a planar-lightwave circuit that includes a surface-waveguide-based mirror and a ring resonator that enables four-wave mixing, where the surface-waveguide mirror and the ring resonator reside within the gain cavity of the laser itself. As a result, photon-pair sources in accordance with the present disclosure can have: (1) a larger free-spectral range for the entire laser cavity to enable generation of a single wavelength to realize single-mode operation without additional stabilization; and (2) low laser noise, thereby enabling detection and use of the generated photon pairs.

A photon source includes a bus waveguide, a photon source pump laser coupled to the bus waveguide and a plurality of optical resonators coupled to the bus waveguide. Each optical resonator of the plurality of optical resonators has a respective resonance line width and a respective resonance frequency, wherein a bandwidth of the resonant center frequencies of the plurality of optical resonators is greater than a bandwidth of the photon source pump laser. The bus waveguide produces photons in response to receiving laser pulses from the pump laser.

A quasi-deterministic single-photon source and method of generating single photons on demand are disclosed. The single-photon source includes photon pair generation for generating a heralding and heralded photon in a frequency-correlated photon pair, a single-photon spectrometer adapted to detect the heralding photon and to generate an output signal that is indicative of the frequency of the detected heralding photon, a pulse shaper arrangement for reshaping a broadband pulse, and an optical frequency conversion means for converting, upon irradiation with a reshaped pulse, a heralded photon into a single output photon with deterministic source frequency. The pulse shaper arrangement is configured to select, based on the spectrometer output signal, only frequency components of the broadband pulse that substantially coincide with the heralding photon frequency or with a constant detuning thereof.

A photon source includes a bus waveguide, a photon source pump laser coupled to the bus waveguide and a plurality of optical resonators coupled to the bus waveguide. Each optical resonator of the plurality of optical resonators has a respective resonance line width and a respective resonance frequency, wherein a bandwidth of the resonant center frequencies of the plurality of optical resonators is greater than a bandwidth of the photon source pump laser. The bus waveguide produces photons in response to receiving laser pulses from the pump laser.

Bright entangled photon sources including an alignment-free, fiber-based, mechanically-rugged and generic interferometric module are disclosed. The inherent phase-stability of a Sagnac interferometer is deployed. High down-conversion efficiency of periodically poled nonlinear-waveguides is combined with the optical gain of semiconductor optical amplifiers and immunity of fiber optics. A single compact interferometric engine combines these attributes, allowing highly stable, integrable and bright polarization entangled-photon sources operating at room temperature. Using a minimum number of in-line optical parts, the compact module is based on a novel method that enhances the long-term stability and efficiency without compromising the entanglement quality. Besides energy entanglement, polarization entanglement is presented and set through the operational conditions. An optional periodically poled nonlinear waveguide can be hosted to achieve the desired spectral bandwidth and photons generation rate. The result is a zero-maintenance, lightweight, low-power consumption engine of compact and fully-integrable bright polarization-entangled photon sources.

An optical ring resonator that includes a closed loop core, a cladding layer, and one or more bus waveguides. The closed loop core is disposed in the cladding layer and is As.sub.2Se.sub.3 glass. The one or more bus waveguides are disposed in the cladding layer and are optically coupled to the closed loop core. The closed loop core has a zero-dispersion wavelength within a telecommunication wavelength band. The closed loop core has a plurality of resonant modes, including a zero-dispersion resonant mode corresponding with the zero-dispersion wavelength and a plurality of paired resonant modes. Further, the closed loop core has a phase matching bandwidth extending greater than ±40 nm from the zero-dispersion wavelength.

A photon source includes a bus waveguide, a photon source pump laser coupled to the bus waveguide and a plurality of optical resonators coupled to the bus waveguide. Each optical resonator of the plurality of optical resonators has a respective resonance line width and a respective resonance frequency, wherein a bandwidth of the resonant center frequencies of the plurality of optical resonators is greater than a bandwidth of the photon source pump laser. The bus waveguide produces photons in response to receiving laser pulses from the pump laser.