A semiconductor-superconductor hybrid device comprises a semiconductor component having first and second terminals, first and second gate electrodes for electrostatically gating the first and second terminals. A second gate electrode electrostatically gates the second terminal, and a superconductor component is configured for energy level hybridisation with the semiconductor component. A method of measuring a non-local conductance of the semiconductor component comprises applying a first gate voltage to the first gate electrode to gate the first terminal to an open regime, applying a second gate voltage to the second gate electrode to gate the second terminal to a tunnelling regime, applying a bias voltage to the first terminal, and while applying the first gate voltage, the second gate voltage, and the bias voltage, measuring a current through the second terminal; with the superconductor component grounded.

Methods, devices, and systems are described for performing quantum operations. An example device at least one magnetic field source configured to supply an inhomogeneous magnetic field, at least one semiconducting layer, and one or more conducting layers configured to: define at least two quantum states in the at least one semiconducting layer, and cause, based on an oscillating electrical signal supplied by the one or more conducting layers, an electron to move back and forth between the at least two quantum states in the presence of the inhomogeneous magnetic field. The movement of the electron between the at least two quantum states may generate an oscillating magnetic field to drive a quantum transition between a spin-up state and spin-down state of the electron thereby implementing a qubit gate on a spin state of the electron.

The method of performing braiding operations can include providing a first Josephson junction including first gates. The method can include providing a second Josephson junction including second gates. The method can include tuning the first gates to dispose a first pair of Majorana fermions a first region. The method can include tuning the second gates to dispose a second pair of Majorana fermions in a second region. The method can include tuning the first gates to dispose a first Majorana fermion in the first region and to dispose a second Majorana fermion in a third region. The method can include tuning the second gates to dispose a third Majorana fermion in a fourth region and to dispose a fourth Majorana fermion in the second region.

A digital circuit includes at least one quantum wire resonant tunneling transistor that includes an emitter terminal, a base terminal, a collector terminal, an emitter region in connection with the emitter terminal, a base region in connection with the base terminal, a collector region in connection with the collector terminal, an emitter barrier region between the emitter region and the base region, and a collector barrier region between the collector region and the base region. At least one of the emitter region, the base region, and the collector region includes a plurality of metal quantum wires.

A qubit coupling device includes: a dielectric substrate including a trench; a first superconductor layer on a surface of the dielectric substrate where an edge of the first superconductor layer extends along a first direction and at least a portion of the superconductor layer is in contact with the surface of the dielectric substrate, and where the superconductor layer is formed from a superconductor material exhibiting superconductor properties at or below a corresponding critical temperature; a length of the trench within the dielectric substrate is adjacent to and extends along an edge of the first superconductor layer in the first direction, and where the electric permittivity of the trench is less than the electric permittivity of the dielectric substrate.

A mixed semiconductor-superconductor platform is fabricated in phases. In a masking phase, a dielectric mask is formed on a substrate, such that the dielectric mask leaves one or more regions of the substrate exposed. In a selective area growth phase, a semiconductor material is selectively grown on the substrate in the one or more exposed regions. In a superconductor growth phase, a layer of superconducting material is formed, at least part of which is in direct contact with the selectively grown semiconductor material. The mixed semiconductor-superconductor platform comprises the selectively grown semiconductor material and the superconducting material in direct contact with the selectively grown semiconductor material.

A mixed semiconductor-superconductor platform is fabricated in phases. In a masking phase, a dielectric mask is formed on a substrate, such that the dielectric mask leaves one or more regions of the substrate exposed. In a selective area growth phase, a semiconductor material is selectively grown on the substrate in the one or more exposed regions. In a superconductor growth phase, a layer of superconducting material is formed, at least part of which is in direct contact with the selectively grown semiconductor material. The mixed semiconductor-superconductor platform comprises the selectively grown semiconductor material and the superconducting material in direct contact with the selectively grown semiconductor material.

A tunable dissipative circuit is presented for shifting a frequency of a radio frequency signal or microwave signal in a cryogenically cooled environment. One or more couplers make couplings between a propagation path and a tunable resonance element and a controllable dissipator element. A first control input to said tunable resonance element allows changing a resonance frequency of said tunable resonance element with a first control signal. A second control input to said controllable dissipator element allows changing a damping rate of said controllable dissipator element with a second control signal.

A tunable dissipative circuit is presented for shifting a frequency of a radio frequency signal or microwave signal in a cryogenically cooled environment. One or more couplers make couplings between a propagation path and a tunable resonance element and a controllable dissipator element. A first control input to said tunable resonance element allows changing a resonance frequency of said tunable resonance element with a first control signal. A second control input to said controllable dissipator element allows changing a damping rate of said controllable dissipator element with a second control signal.

A quantum bit array is disclosed. In an embodiment, the quantum bit array includes a control gate coupled to a qubit and at least one pass gate coupled between the qubit and an adjacent qubit to control operation of the qubit of the quantum bit array, a bit line, and a first transistor channel that connects the bit line to the control gate. The array further comprises at least one word line coupled to the first transistor channel. The at least one word line selectively controls charge flow through the first transistor channel. The array further comprises a capacitor coupled to selectively store charge in the first transistor channel.