The various embodiments described herein include methods, devices, and circuits for reducing switch transition time of superconductor switches. In some embodiments, an electrical circuit includes: (i) an input component configured to generate heat in response to an electrical input; and (ii) a first superconducting component thermally-coupled to the input component. The electrical circuit is configured such that, in the absence of the electrical input, at least a portion of the first superconducting component is maintained in a non-superconducting state in the absence of the electrical input; and, in response to the electrical input, the first superconducting component transitions to a superconducting state.

Single-photon detector apparatus comprising a large core optical fiber with a core diameter larger than 8 .Math.m, a small core optical fiber with a core diameter smaller or equal to 5 .Math.m, a taper between the large core optical fiber and the small core optical fiber, a superconducting nanowire having a surface area configured to receive all photons emitted from the small core optical fiber and cost effective and high yield method for manufacturing such.

Single-photon detector apparatus comprising a large core optical fiber with a core diameter larger than 8 .Math.m, a small core optical fiber with a core diameter smaller or equal to 5 .Math.m, a taper between the large core optical fiber and the small core optical fiber, a superconducting nanowire having a surface area configured to receive all photons emitted from the small core optical fiber and cost effective and high yield method for manufacturing such.

A quantum device is fabricated by forming a network of nanowires oriented in a plane of a substrate to produce a Majorana-based topological qubit. The nanowires are formed from combinations of selective-area-grown semiconductor material along with regions of a superconducting material. The selective-area-grown semiconductor material is grown by etching trenches to define the nanowires and depositing the semiconductor material in the trenches. A side gate is formed in an etched trench and situated to control a topological segment of the qubit.

A quantum device is fabricated by forming a network of nanowires oriented in a plane of a substrate to produce a Majorana-based topological qubit. The nanowires are formed from combinations of selective-area-grown semiconductor material along with regions of a superconducting material. The selective-area-grown semiconductor material is grown by etching trenches to define the nanowires and depositing the semiconductor material in the trenches. A side gate is formed in an etched trench and situated to control a topological segment of the qubit.

The various embodiments described herein include methods, devices, and systems for fabricating and operating superconducting photon detectors. In one aspect, a photon detector includes: (1) a first waveguide configured to guide photons from a photon source; (2) a second waveguide that is distinct and separate from the first waveguide and optically-coupled to the first waveguide; and (3) a superconducting component positioned adjacent to the second waveguide and configured to detect photons within the second waveguide.

Conventional readout of a superconducting nanowire single-photon detector (SNSPD) sets an upper bound on the output voltage to be the product of the bias current and the load impedance, I.sub.B×Z.sub.load, where Z.sub.load is limited to 50Ω in standard RF electronics. This limit is broken/exceeded by interfacing the 50Ω load and the SNSPD using an integrated superconducting transmission line taper. The taper is a transformer that effectively loads the SNSPD with high impedance without latching. The taper increases the amplitude of the detector output while preserving the fast rising edge. Using a taper with a starting width of 500 nm, a 3.6× higher pulse amplitude, 3.7× faster slew rate, and 25.1 ps smaller timing jitter was observed. The taper also makes the detector's output voltage sensitive to the number of photon-induced hotspots and enables photon number resolution.

A quantum computing device is fabricated by forming, on a superconductor layer, a first resist pattern defining a device region and a sensing region within the device region. The superconductor layer within the sensing region is removed, exposing a region of an underlying semiconductor layer outside the device region. The exposed region of the semiconductor layer is implanted, forming an isolation region surrounding the device region. Using an etching process subsequent to the implanting, the sensing region and a portion of the device region of the superconductor layer adjacent to the isolation region are exposed. By depositing a first metal layer within the sensing region, a tunnel junction gate is formed. A reflectrometry wire comprising a second metal within the reflectrometry region is formed. A nanorod contact using the second metal within the portion of the device region outside the sensing region is formed.

An electronic device includes a substrate and a layer of superconducting material disposed over the substrate. The layer of superconducting material includes a first wire and a loop that is (1) distinct and separate from the first wire and (ii) capacitively coupled to the first wire while the loop and the first wire are in a superconducting state.

A particle detector according to one embodiment includes: superconductive lines, conductive lines, insulating films, a first detection circuit, and a second detection circuit. The superconductive lines extend in a first direction and are arranged in a second direction intersecting the first direction. The conductive lines extend in a third direction different from the first direction and are arranged in a fourth direction intersecting the third direction. The insulating films are each interposed at an intersection point between one of the superconductive lines and one of the conductive lines. The first detection circuit detects a voltage change occurring in the superconductive lines. The second detection circuit detects a current or a voltage generated in the conductive lines when the voltage change occurs.