Abstract: A waveguide structure includes a substrate, a waveguide core coupled to the substrate and including a first material characterized by a first index of refraction, and an isotope-enhanced cladding layer at least partially surrounding the waveguide core and including a second material characterized by a second index of refraction less than the first index of refraction and an isotope-enhanced Pockels effect.

Abstract: In some embodiments a method comprises depositing a first silicon nitride layer on a top surface of a semiconductor wafer and forming one or more first gaps in the first silicon nitride layer. The one or more first gaps can relieve stress formed in the first silicon nitride layer. A first fill material is deposited on the first silicon nitride layer and the first silicon nitride layer is planarized. A second silicon nitride layer is deposited across the first silicon nitride layer and one or more second gaps are formed in the second silicon nitride layer. The one or more second gaps can relieve stress formed in the second silicon nitride layer. A second fill material is deposited across the second silicon nitride layer and the second silicon nitride layer is planarized.

Abstract: An electro-optic device includes a substrate and a waveguide on the substrate. The waveguide includes a layer stack including a plurality of electro-optic material layers interleaved with a plurality of interlayers, a waveguide core adjacent to the layer stack, a waveguide cladding layer, and a pair of electrodes in electrical contact with the plurality of electro-optic material layers. The plurality of interlayers maintains a first lattice structure at room temperature and a cryogenic temperature. The plurality of electro-optic material layers maintains a second lattice structure and crystallographic phase at the room temperature and the cryogenic temperature.

Abstract: A photon source module includes a plurality of photon sources, wherein each photon source is configured to non-deterministically generate one or more non-entangled or entangled photons in response to receiving a trigger signal. When two or more photon sources simultaneously generate photons in response to a trigger signal, one photon of a first photon pair is directed to a photon processing system and one photon of a second photon pair is directed to a photon analyzer. During repetitive operation, the photon analyzer analyzes photons from each of the plurality of photon sources to determine characteristics of each photon source and can use that information to direct the highest quality photons to the photon processing system.

Abstract: Circuits and methods that implement multiplexing for photons propagating in waveguides are disclosed, in which an input photon received on a selected one of a set of input waveguides can be selectably routed to one of a set of output waveguides. The output waveguide can be selected on a rotating or cyclic basis, in a fixed order, and the input waveguide can be selected based at least in part on which one(s) of a set of input waveguides is (are) currently propagating a photon.

Abstract: A Mach-Zehnder interferometer (MZI) filter comprising one or more passive compensation structures are described. The passive compensation structures yield MZI filters that are intrinsically tolerant to perturbations in waveguide dimensions and/or other ambient conditions. The use of n+1 waveguide widths can mitigate n different sources of perturbation to the filter. The use of at least three different waveguide widths for each Mach-Zehnder waveguide can alleviate sensitivity of filter performance to random width or temperature variations. A tolerance compensation portion is positioned between a first coupler section and a second coupler section, wherein the tolerance compensation portion includes a first compensation section having a second width, a second compensation section having a third width and a third compensation section having a fourth width, wherein the fourth width is greater than the third width and the third width is greater than the second width.

Abstract: 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.

Abstract: An optical switch structure includes a substrate, a first electrical contact, a first material having a first conductivity type electrically connected to the first electrical contact, a second material having a second conductivity type coupled to the first material, and a second electrical contact electrically connected to the second material. The optical switch structure also includes a waveguide structure disposed between the first electrical contact and the second electrical contact and comprising a waveguide core coupled to the substrate and including a first material characterized by a first index of refraction and a first electro-optic coefficient and a waveguide cladding at least partially surrounding the waveguide core and including a second material characterized by a second index of refraction and a second electro-optic.

Abstract: A device (e.g., a photonic multiplexer) is provided that includes a plurality of first switches. Each first switch in the plurality of first switches includes a plurality of first channels. Each first switch is configured to shift photons in the plurality of first channels by zero or more channels, based on first configuration information provided to the first switch. The device further includes a plurality of second switches. Each second switch includes a plurality of second channels. Each second channel is coupled with a respective first channel from a distinct first switch of the plurality of first switches. Each second switch is configured to shift photons in the plurality of second channels by zero or more channels, based on second configuration information provided to the second switch.

Abstract: Techniques disclosed herein relate to photon sources with high spectral purity and high brightness. In one embodiment, a photon-pair source includes a pump waveguide, a first resonator coupled to the pump waveguide to couple pump photons from the pump waveguide into the first resonator, a second resonator coupled to the first resonator, and an output waveguide coupled to the second resonator. The second resonator is configured to convert the pump photons into photon pairs. The second resonator and the first resonator are configured to cause a coupling-induced resonance splitting in the second resonator or the first resonator. The second resonator and the output waveguide are configured to couple the photon pairs from the second resonator into the output waveguide. In some embodiments, the photo-pair source includes one or more tuners for tuning at least one of the first resonator or the second resonator.

Abstract: A method includes receiving input light having an input wavelength in a first optical resonator for causing resonance of the input light in the first optical resonator. The first optical resonator includes a non-linear optical medium. The method also includes converting at least a portion of the input light to a combination of first output light having a first output wavelength that is different from the input wavelength and second output light having a second output wavelength that is different from the input wavelength and the first output wavelength by passing the input light through the non-linear optical medium. The method further includes causing resonance of the first output light and the second output light in a second optical resonator. A portion of the first optical resonator is coupled to a portion of the second optical resonator.

Abstract: 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.

Abstract: Optical circuits support reconfigurable spatial rearrangement (also referred to as “spatial multiplexing”) for a group of photons propagating in waveguides. According to some embodiments, a set of 2×2 muxes can be used to rearrange a pattern of photons on a first set of waveguides into a usable input pattern for a downstream optical circuit.

Abstract: An expanded Bell state generator can generate a Bell state on four output modes of a set of m output modes, where m is greater than four. Some expanded Bell state generators can receive inputs on any four of a set of 2m input modes. Subsets of the m output modes can be multiplexed to reduce the number of modes to four. According to some embodiments, a set of 2×2 muxes can be used to rearrange the output modes prior to reducing the number of modes.

Abstract: A method of forming a film comprises growing, using a deposition system, at least a portion of the film and analyzing, using a RHEED instrument, the at least a portion of the film. Using a computer, data is acquired from the RHEED instrument that is indicative of a stoichiometry of the at least a portion of the film. Using the computer, adjustments to one or more process parameters of the deposition system are calculated to control stoichiometry of the film during subsequent deposition. Using the computer, instructions are transmitted to the deposition system to execute the adjustments of the one or more process parameters. Using the deposition system, the one or more process parameters are adjusted.

Abstract: A device includes a plurality of superconducting components, each having a first terminal and a second terminal; a plurality of current sources, being electrically-connected to the first terminal of a corresponding superconducting component and configured to selectively provide a first current; and a bias current source electrically-connected to the respective first terminal of each of the plurality of superconducting components. The bias current source is configured to provide a second current adapted to bias the superconducting components such that (1) a combination of the second current and the first current from each current source causes the plurality of superconducting components to transition from the superconducting state to the non-superconducting state, and (2) a combination of the second current and the first current from each current source of only a subset of the plurality of current sources does not cause the plurality of superconducting components to transition to the non-superconducting state.

Abstract: A method of generating an m photon entangled state includes inputting a photon into each of a first plurality of modes including first and second pairs of modes. The first plurality of modes is coupled with a second plurality of modes. Zero or more photons are detected in the second plurality of modes. The method includes, when more than m photons remain in the first plurality of modes: detecting zero or more photons in a third plurality of modes coupled with the first plurality of modes; determining, based on a number of photons detected, whether the photons remaining in the first plurality of modes are in the entangled state. The method includes, when the photons remaining in the first plurality of modes after the second detection operation are in the entangled state, outputting the photons remaining in the first plurality of modes.

Abstract: 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.

Abstract: An assembly system for assembling an optical die to an optical substrate includes test equipment configured to test optical couplers formed between the optical die and the optical substrate. The assembly system is configured to adjust an alignment of the optical die relative to the optical substrate until the optical couplers meet a performance metric. After the performance metric is met the optical die is permanently attached to the optical substrate.

Abstract: Techniques disclosed herein relate generally to integrating photonic integrated circuits and electronic integrated circuits in a same package. A device includes a semiconductor substrate and a die stack on the semiconductor substrate. The die stack includes a photonic integrated circuit (PIC) die and an electronic integrated circuit (EIC) die. The PIC die includes a PIC substrate and a photonic integrated circuit formed on the PIC substrate. The EIC die includes an EIC substrate and an electronic integrated circuit formed on the EIC substrate. The EIC die and the PIC die are bonded such that the PIC substrate and the EIC substrate are disposed on opposing sides of the die stack. The PIC substrate is bonded to the semiconductor substrate. The device also includes a cooling plate bonded to the EIC substrate.