A reversible memory element is provided. The reversible memory element comprises a reversible memory cell comprising a Josephson junction and a passive inductor. A ballistic interconnect is connected to the reversible memory cell by a bidirectional input/output port. A polarized input fluxon propagating along the ballistic interconnect exchanges polarity with a stationary stored fluxon in the reversible memory cell in response to the input fluxon reflecting off the reversible memory cell.

An apparatus includes a substrate, a classical computing processor formed on the substrate, a quantum computing processor formed on the substrate, and one or more coupling components between the classical computing processor and the quantum computing processor, the one or more coupling components being formed on the substrate and being configured to allow data exchange between the classical computing processor and the quantum computing processor.

A multi-mode resonator is provided. The multi-mode resonator includes a housing and a cavity disposed in the housing, wherein the cavity includes a main cavity and a plurality of first subcavities disposed on a first lateral side of the main cavity.

Quantum information processing apparatus and methods are described. The apparatus comprises a device for defining a qubit and a reflectometry circuit for reading out a state of the qubit. The device comprises a semiconductor nanowire extending along a first direction having first and second obtuse or acute edges running along the first direction, gate dielectric overlying the first and second edges of the nanowire and a split gate running across a section of the nanowire in a second, transverse direction, the split gate comprising first and second gates overlying the first and second edges respectively. The reflectometry circuit comprises a resonator coupled to the first or second gate.

In an integrated-circuit component having a signal transmitter receives a transmitter power supply that cycles periodically between power-off and power-on voltage levels to define a sequence of enable intervals during which the signal transmitter is to output voltage levels corresponding to respective transmit data bits onto an external signaling link. The signal transmitter generates, at the start of each output-enable interval, an initial nonzero voltage having a first polarity across conductors of the external signaling link, and then conditionally transitions the initial nonzero voltage to a second nonzero voltage according to whether the transmit data bit corresponding to the output-enable interval has a predetermined one of two binary states, the second nonzero voltage having a polarity opposite the first polarity.

Various techniques and apparatus permit fabrication of superconductive circuits. A niobium/aluminum oxide/niobium trilayer may be formed and individual Josephson Junctions (JJs) formed. A protective cap may protect a JJ during fabrication. A hybrid dielectric may be formed. A superconductive integrated circuit may be formed using a subtractive patterning and/or additive patterning. A superconducting metal layer may be deposited by electroplating and/or polished by chemical-mechanical planarization. The thickness of an inner layer dielectric may be controlled by a deposition process. A substrate may include a base of silicon and top layer including aluminum oxide. Depositing of superconducting metal layer may be stopped or paused to allow cooling before completion. Multiple layers may be aligned by patterning an alignment marker in a superconducting metal layer.

Method and circuit for reading a value {circumflex over (σ)}.sub.z stored in a quantum information unit (qubit) memory having a qubit frequency ω.sub.a, with a resonator defined by a resonator damping rate κ, a resonator frequency ω.sub.r, a resonator electromagnetic field characterized by â.sup.† and â, a longitudinal coupling strength g.sub.z, an output â.sub.out and a longitudinal coupling g.sub.z{circumflex over (σ)}.sub.z(â.sup.†+â). At a quantum non-demolition (QND) longitudinal modulator, periodically modulating the longitudinal coupling strength g.sub.z with a signal of amplitude {tilde over (g)}.sub.z at least three (3) times greater than the resonator damping rate κ and of frequency ω.sub.m with ω.sub.m+κ resonant with ω.sub.r, wherein the longitudinal coupling strength g.sub.z varies over time (t) in accordance with g.sub.z(t)=g.sub.z+{tilde over (g)}.sub.z cos(ω.sub.mt) with g.sub.z representing an average value of g.sub.z and at a QND homodyne detector, measuring the value {circumflex over (σ)}.sub.z of the qubit memory from a phase reading of the output {circumflex over (σ)}.sub.out.

Systems and devices for providing differential input/output communication with a superconducting device are described. Each differential I/O communication is electrically filtered using a respective tubular filter structure incorporating superconducting lumped element devices and high frequency dissipation by metal powder epoxy. A plurality of such tubular filter structures is arranged in a cryogenic, multi-tiered assembly further including structural/thermalization supports and a device sample holder assembly for securing a device sample, for example a superconducting quantum processor. The interface between the cryogenic tubular filter assembly and room temperature electronics is achieved using hermetically sealed vacuum feed-through structures designed to receive flexible printed circuit board cable.

Magneto-optical modulator-based systems and devices for transferring quantum information are described. Such systems can be used for many applications, including as part of quantum computers. An example system includes a quantum information system configured to provide a signal corresponding to at least one qubit. The system further includes a magneto-optical driver configured to receive the signal corresponding to the at least one qubit and process the signal to generate a current based on the signal corresponding to the at least one qubit. The system further includes a magneto-optical modulator configured to receive the current from the magneto-optical driver and provide a modulated light output by modulating a received light input based on the current.

An oscillator in which crosstalk can be reduced is provided. An oscillator includes a ground plane made of a superconductor, a conductive member spaced apart from and surrounded by the ground plane, a SQUID of which one end is connected to the conductive member and the other end is connected to the ground plane, a first connection circuit made of a superconductor, connecting parts of the ground plane located on both sides of a vicinity of a connection part between the conductive member and the SQUID to each other, and a superconducting loop circuit surrounding the SQUID and using the ground plane and the first connection circuit.