A superconductor bulk magnet magnetizing method providing a more homogenous trapped magnetic field includes: placing the bulk magnet inside a charger bore of an electrical charger magnet; placing a field correction unit inside a superconductor bore of the bulk magnet; applying an electrical current (I.sub.0) to the charger magnet, to generate an externally applied magnetic field, wherein a temperature T.sub.bulk of the bulk magnet exceeds a bulk magnet critical temperature T.sub.c; applying an auxiliary electrical current (I.sub.1, . . . ) to the field correction unit, thus generating an auxiliary magnetic field applied to the bulk magnet from within the superconductor bore, wherein T.sub.bulk>T.sub.c; lowering T.sub.bulk below T.sub.c; turning off the electrical current at the charger magnet, wherein T.sub.bulk<T.sub.c, and turning off the auxiliary electrical current at the field correction unit, wherein T.sub.bulk<T.sub.c; and removing the bulk magnet from the charger bore while T.sub.bulk<T.sub.c.

A superconducting magnetic levitation train includes a frame, an arm, a first support member, a Dewar, a permanent magnet track, an iron core, a coil, a DC power supply system, and a second support member. the arm is arranged on a bottom of the frame; the Dewar 4 with bulk superconductors or superconducting magnets inside is arranged on the bottom of the frame 1; a bottom of the first support member and the second support member is fixedly arranged on a ground; the permanent magnet track is arranged on the first support member; the iron core is arranged on the second support member; the coil is sleeved on the iron core; and levitation, guidance and propulsion integrated superconducting magnetic levitation train further comprises a direct current (DC) power supply system to supply power to the coil.

One example includes a superconducting current control system. The system includes an inductive coupler comprising a load inductor and a control inductor. The inductive coupler can be configured to inductively provide a control current from the control inductor to a superconducting circuit device based on a load current being provided through the load inductor. The system also includes a current control element comprising a superconducting quantum interference device (SQUID) array comprising a plurality of SQUIDs. The current control element can be coupled to the inductive coupler to control an amplitude of the load current through the load inductor, and thus to control an amplitude of the control current to the superconducting circuit device.

Quantum computing systems require methods to control energies of qubits and couplers for quantum operations. Flux biasing of qubits and quantum couplers is provided for a superconducting quantum computer using single-flux-quantum (SFQ) technology. This method is applicable to a wide range of superconducting qubit structures and couplers, including transmons, fluxoniums, flux qubits, phase qubits and other superconducting qubits. This method enables arbitrary-amplitude time-varying flux biasing of qubits and couplers, due to a sequence of high-speed SFQ pulses. Several preferred embodiments are disclosed which provide high-fidelity control of fast single-qubit and multi-qubit operations.

Charging method for a superconductor magnet system with reduced stray field, weight and space includes: arranging the system within a charger magnet bore; with T.sub.main>T.sub.main.sup.crit and T.sub.shield>T.sub.shield.sup.crit, applying a current I.sub.charger to the charger magnet and increasing I.sub.charger to a first current I.sub.1>0; lowering a main superconductor bulk magnet temperature T.sub.main to an operation temperature T.sub.main.sup.op, with T.sub.main.sup.op<T.sub.main.sup.crit, while keeping T.sub.shield>T.sub.shield.sup.crit; lowering I.sub.charger to a second current I.sub.2<0, thereby inducing a persistent current IP.sub.main in the main magnet; lowering a shield magnet temperature T.sub.shield to an operation temperature T.sub.shield.sup.op, with T.sub.shield.sup.op<T.sub.shield.sup.crit; increasing I.sub.charger to zero, thereby inducing a persistent current IP.sub.shield in the shield magnet; removing the magnet system from the charger bore, and keeping T.sub.main≤T.sub.main.sup.op with T.sub.main.sup.op<T.sub.main.sup.crit and T.sub.shield≤T.sub.shield.sup.op with T.sub.shield.sup.op<T.sub.shield.sup.crit; where: T.sub.main.sup.crit: main magnet critical temperature and T.sub.shield.sup.crit: shield magnet critical temperature.

Charging method for a superconductor magnet system with reduced stray field, weight and space includes: arranging the system within a charger magnet bore; with T.sub.main>T.sub.main.sup.crit and T.sub.shield>T.sub.shield.sup.crit, applying a current I.sub.charger to the charger magnet and increasing I.sub.charger to a first current I.sub.1>0; lowering a main superconductor bulk magnet temperature T.sub.main to an operation temperature T.sub.main.sup.op, with T.sub.main.sup.op<T.sub.main.sup.crit, while keeping T.sub.shield>T.sub.shield.sup.crit; lowering I.sub.charger to a second current I.sub.2<0, thereby inducing a persistent current IP.sub.main in the main magnet; lowering a shield magnet temperature T.sub.shield to an operation temperature T.sub.shield.sup.op, with T.sub.shield.sup.op<T.sub.shield.sup.crit; increasing I.sub.charger to zero, thereby inducing a persistent current IP.sub.shield in the shield magnet; removing the magnet system from the charger bore, and keeping T.sub.main≤T.sub.main.sup.op with T.sub.main.sup.op<T.sub.main.sup.crit and T.sub.shield≤T.sub.shield.sup.op with T.sub.shield.sup.op<T.sub.shield.sup.crit; where: T.sub.main.sup.crit: main magnet critical temperature and T.sub.shield.sup.crit: shield magnet critical temperature.

A superconductor magnetic field effect transistor. The superconductor magnetic field effect transistor may include a sheet of a superconducting material; and a solenoid. The sheet may be substantially flat, and the solenoid may include a plurality of turns, each of the turns being substantially parallel to the sheet. The superconducting material may be a type-II superconducting material.

A superconductor magnetic field effect transistor. The superconductor magnetic field effect transistor may include a sheet of a superconducting material; and a solenoid. The sheet may be substantially flat, and the solenoid may include a plurality of turns, each of the turns being substantially parallel to the sheet. The superconducting material may be a type-II superconducting material.

In examples, provided are leadless power couplers that include (1) a thermal insulating system having an outer wall and an inner wall, (2) a first electrically conductive winding located outside the thermal insulating system, where the first electrically conductive winding is configured to create a varying magnetic field, (3) a plurality of second electrically conductive windings located inside the thermal insulating system and configured to couple to the varying magnetic field, the plurality of second electrically conductive windings being superconductors, (4) a plurality of cryogenic rectifiers, each cryogenic rectifier being coupled to a respective second electrically conductive winding in the plurality of second electrically conductive windings, and (5) a plurality of cryogenic cables coupled between respective outputs of the plurality of cryogenic rectifiers and respective loads.

A radial-gap type superconducting synchronous machine 1 is prepared which includes a rotor 20 having, on its peripheral side, a convex magnetic pole 21 which includes, at its distal end part, bulk superconductors 30. When viewed in the direction of the rotational axis C1 of the rotor 20, the magnetic pole center side of the bulk superconductors 30 is disposed nearer to a stator 10 than the magnetic pole end side of the bulk superconductors 30. A ferromagnet 28 is disposed on the rotational axis C1 side of the bulk superconductors 30. A magnetizing apparatus 100 is disposed outside the bulk superconductors 30 in the radial direction of the rotor 20. Magnetization of the bulk superconductors 30 is performed by directing magnetic flux lines from the magnetizing apparatus 100 toward the bulk superconductors 30.