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: 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 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: A photonic switch includes a first waveguide including a first region extending between a first coupler section and a second coupler section and a second region extending between the second coupler section and a third coupler section. The photonic switch also includes a second waveguide including a first portion extending between the first coupler section and the second coupler section, the first portion including at least two first compensation sections each having a different waveguide width, and a second portion extending between the second coupler section and the third coupler section, the second portion including at least two second compensation sections each having a different waveguide width. The photonic switch further includes at least one variable phase-shifter disposed in at least one of the first waveguide or the second waveguide.

Abstract: A method and a device for correcting quantum state information are disclosed. A decoder receives information identifying syndrome values for a plurality of entangled qubit states represented by a graph state with a respective edge of the graph state corresponding to a respective qubit state of the plurality of entangled qubit states. The decoder repeats identifying one or more clusters of qubit states and/or syndrome states in the graph state until all of the one or more identified clusters are determined to be valid while increasing a size of a respective cluster each time the identifying operation is performed. The decoder reconstructs one or more qubit states and/or syndrome states for respective clusters; and stores information identifying the one or more reconstructed qubit states and/or syndrome states.

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: An optical switch structure includes at least one optical input port and at least one optical output port. The optical switch structure also includes an optical waveguide structure including a waveguide core and a waveguide cladding The optical waveguide structure is optically coupled to the at least one optical input port and the at least one optical output port. The waveguide core includes a first material characterized by a first index of refraction and a first electro-optic coefficient and the waveguide cladding includes a second material characterized by a second index of refraction less than the first index of refraction and a second electro-optic coefficient greater than the first electro-optic coefficient.

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: A superconducting circuit includes a first component having a first connection point. The first connection point has a first width. The superconducting circuit includes a second component having a second connection point. The second connection point has a second width that is larger than the first width. The superconducting circuit includes a superconducting connector shaped to reduce current crowding. The superconducting connector electrically connects the first connection point and the second connection point. The superconducting connector includes a first taper positioned adjacent the first connection point and having a non-linear shape and a second taper positioned adjacent the second connection point.

Abstract: A device includes a superconductor layer and a piezoelectric layer positioned adjacent to the superconductor layer. The piezoelectric layer is configured to apply a first strain to the superconductor layer in response to receiving a first voltage that is below a predefined voltage threshold and to apply a second strain to the superconductor layer in response to receiving a second voltage that is above the predefined voltage threshold. While the device is maintained below a superconducting threshold temperature for the superconductor layer and is supplied with current below a superconducting threshold current for the superconductor layer, the superconductor layer is configured to 1) operate in a superconducting state when the piezoelectric layer applies the first strain to the superconductor layer and 2) operate in an insulating state when the piezoelectric layer applies the second strain to the superconductor layer.

Abstract: A method includes receiving a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another. The method further includes performing a plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data and determining, by a decoder, a plurality of syndrome graph values based on the joint measurement outcome data.

Abstract: In some embodiments method comprises depositing a ferroelectric layer on a top surface of a semiconductor wafer and forming one or more gaps in the ferroelectric layer. The one or more gaps can be formed on a repetitive spacing to relieve stresses between the ferroelectric layer and the semiconductor wafer. A first dielectric layer is deposited over the ferroelectric layer and the first dielectric layer is planarized to fill in the gaps. A second dielectric layer is formed between the ferroelectric layer and the semiconductor wafer. The second dielectric layer can be formed by annealing the wafer in an oxidizing atmosphere such that an upper portion of the semiconductor substrate forms an oxide layer between the semiconductor substrate and the ferroelectric layer.

Abstract: A programmable circuit includes a superconducting component arranged in a multi-dimensional array of alternating narrow and wide portions. The programmable circuit further includes a plurality of heat sources, each heat source configured to selectively provide heat to a respective narrow portion sufficient to transition the respective narrow portion from a superconducting state to a non-superconducting state. The programmable circuit further includes a plurality of electrical terminals, each electrical terminal coupled to a respective wide portion of the multi-dimensional array.

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: The various embodiments described herein include methods, devices, and systems for fabricating and operating transistors. In one aspect, a transistor includes: (1) a semiconducting component configured to operate in an on state at temperatures above a semiconducting threshold temperature; and (2) a superconducting component configured to operate in a superconducting state while: (a) a temperature of the superconducting component is below a superconducting threshold temperature; and (b) a first current supplied to the superconducting component is below a current threshold; where: (i) the semiconducting component is located adjacent to the superconducting component; and (ii) in response to a first input voltage, the semiconducting component is configured to generate an electromagnetic field sufficient to lower the current threshold such that the first current exceeds the lowered current threshold, thereby transitioning the superconducting component to a non-superconducting state.

Abstract: The various embodiments described herein include methods, devices, and systems for fabricating and operating diodes. In one aspect, an electrical circuit includes: (1) a diode component having a particular energy band gap; (2) an electrical source electrically coupled to the diode component and configured to bias the diode component in a particular state; and (3) a heating component thermally coupled to a junction of the diode component and configured to selectively supply heat corresponding to the particular energy band gap.

Abstract: An optical device includes a first multi-mode waveguide, a first optical coupler coupled to the first multi-mode waveguide, the first coupler being tapered and curved, and a first single-mode waveguide having a first end coupled to the first optical coupler. The optical device maybe used in an optical delay device. A method of propagating light in a first multi-mode waveguide toward a first optical coupler, propagating the light in the first optical coupler toward a first single-mode waveguide, the first optical coupler being tapered and curved, and propagating the light along the first single-mode waveguide is also disclosed.

Abstract: An electronic component having an asymmetric impedance is provided. The component includes first, second and third branches that connect at a common node. The component includes a first portion of superconducting material disposed along the first branch and a second portion of superconducting material disposed along the second branch. The component includes a first device disposed along the first branch and configured to transition the second portion of the superconducting material to a non-superconducting state when a current between a first terminal of the first device and a second terminal of the first device exceeds a first threshold value and a second device disposed along the second branch and configured to transition the first portion of the superconducting material to a non-superconducting state when a current between a first terminal of the second device and a second terminal of the second device exceeds a second threshold value.

Abstract: The present disclosure provides a circuit that includes a first component and a plurality of superconducting wires thermally-coupled to the first component. The superconducting wires of the plurality of superconducting wires are arranged and configured such that a threshold superconducting current for each superconducting wire is dependent on an amount of heat received from the first component. The circuit further includes a dielectric material separating the plurality of superconducting wires from one another. A superconducting wire nearest the first component among the plurality of superconducting wires is more than a phonon mean free path of the dielectric material from the first component. The circuit further includes control circuitry electrically-coupled to the plurality of superconducting wires and configured to provide current to each of the plurality of superconducting wires.

Abstract: An optical device includes a first waveguide that includes a plurality of first portions coupled with regions doped with first dopants, and a plurality of second portions coupled with regions doped with second dopants, distinct from the first dopants, the plurality of first portions being interleaved with the plurality of second portions. And the optical device includes a second waveguide located adjacent to the first waveguide for coupling light from the first waveguide to the second waveguide. The second waveguide includes a third portion coupled with a third region doped with the first dopants and a fourth portion coupled with a fourth region doped with the second dopants, wherein the first portion is located adjacent to the third portion and the second portion is located adjacent to the fourth portion.