One example includes a tunable current element. The element includes a first magnetic flux component that is configured to exhibit a bias flux in response to a first control current. The bias flux can decrease relative energy barriers between discrete energy states of the tunable current element. The element also includes a second magnetic flux component that is configured to exhibit a control flux in response to a second control current. The control flux can change a potential energy of the discrete energy states of the tunable current element to set an energy state of the tunable current element to one of the discrete energy states, such that the magnetic flux component is configured to generate a hysteretic current that provides a magnetic flux at an amplitude corresponding to the energy state of the tunable current element.

A communication system using vector and scalar potential is disclosed. The system uses field-free potentials signaling for many applications where the absence of shielding effects in sea water, plasma or other dense media due to the fact that the absence of (E,B) fields eliminates the possibility of induced charge and current response in the media being transited.

A magnetic field measuring apparatus includes a digital FLL circuit. The digital FLL circuit includes a first amplifier configured to amplify voltage output by a superconducting quantum interference device in accordance with strength of a magnetic field strength, an AD converter configured to, convert analog signals to first digital values, an integrator configured to integrate the first digital values output by the AD converter, a DA converter configured to receive an integral value output by the integrator as a second digital value, convert the second digital value to voltage, and output the converted voltage, a signal switcher configured to connect an output of the first amplifier or an output of the DA converter to an input of the AD converter, and a storage unit configured to store a correction value that corrects the integral value received by the DA converter.

One example includes a tunable current element. The element includes a first magnetic flux component that is configured to exhibit a bias flux in response to a first control current. The bias flux can decrease relative energy barriers between discrete energy states of the tunable current element. The element also includes a second magnetic flux component that is configured to exhibit a control flux in response to a second control current. The control flux can change a potential energy of the discrete energy states of the tunable current element to set an energy state of the tunable current element to one of the discrete energy states, such that the magnetic flux component is configured to generate a hysteretic current that provides a magnetic flux at an amplitude corresponding to the energy state of the tunable current element.

A magnetic shielding system that includes a shield that is non-uniform in the axial direction and a shield cap that is non-uniform in the radial direction. Each shield in the system may have a magnetic permeability, thickness, and/or radius that varies in the axial direction to create low-reluctance paths that redirect flux away from a sample towards the ends of the shield. Each shield cap in the system may have a magnetic permeability and/or thickness that varies in the radial direction to create low-reluctance paths that redirect flux away from the sample towards shield walls. An inner shielding layer formed from a material of low permeability and moderate-to-high coercivity may be implemented as the innermost layer of a magnetic shielding system.

One example includes a magnetic flux source system that includes a tunable current element. The tunable current element includes a SQUID inductively coupled to a first control line that conducts a first control current that induces a bias flux in the SQUID to decrease relative energy barriers between discrete energy states of the tunable current element. The system also includes an inductor in a series loop with the SQUID and inductively coupled to a second control line that conducts a second control current that induces a control flux in the series loop to change a potential energy of the discrete energy states of the tunable current element to set an energy state of the tunable current element to one of the discrete energy states to generate a current that provides a magnetic flux at an amplitude corresponding to the energy state of the at least one tunable current element.

A circuit includes a Superconducting Quantum Interference Array (SQIF), a bias circuit, and a coil. The SQIF generates an output voltage that is a transfer function of the magnetic flux perpendicularly passing through the SQIF. An external magnetic field and a bias magnetic field supply the magnetic flux. The bias circuit generates a bias current for biasing the SQIF at an operating point. The coil generates the bias magnetic field through the SQIF from the bias current of the bias circuit. The bias magnetic field provides nullifying feedback to the SQIF that counterbalances a low-frequency portion of the external magnetic field, such that the output voltage of the SQIF detects a high-frequency portion of the external magnetic field. The circuit can be a receiver with the output voltage of the SQIF detecting an electromagnetic signal while the receiver is moving with changing orientation relative to the Earth's magnetic field.

A circuit includes a Superconducting Quantum Interference Array (SQIF), a bias circuit, and a coil. The SQIF generates an output voltage that is a transfer function of the magnetic flux perpendicularly passing through the SQIF. An external magnetic field and a bias magnetic field supply the magnetic flux. The bias circuit generates a bias current for biasing the SQIF at an operating point. The coil generates the bias magnetic field through the SQIF from the bias current of the bias circuit. The bias magnetic field provides nullifying feedback to the SQIF that counterbalances a low-frequency portion of the external magnetic field, such that the output voltage of the SQIF detects a high-frequency portion of the external magnetic field. The circuit can be a receiver with the output voltage of the SQIF detecting an electromagnetic signal while the receiver is moving with changing orientation relative to the Earth's magnetic field.

One example includes a tunable current-mirror qubit. The qubit includes a plurality of flux tunable elements disposed in a circuit loop. A first portion of the flux tunable elements can be configured to receive a first input flux and a remaining portion of the flux tunable elements can be configured to receive a second input flux to control a mode of the tunable current-mirror qubit between a microwave excitation mode to facilitate excitation or quantum state manipulation of the tunable current-mirror qubit via a microwave input signal and a noise-protected mode to facilitate storage of the quantum state of the tunable current-mirror qubit. The qubit also includes at least one capacitor interconnecting nodes between respective pairs of the flux tunable elements to facilitate formation of Cooper-pair excitons in each of the microwave excitation mode and the noise-protected mode.

A quantum computing device includes multiple co-planar waveguide flux qubits, at least one coupler element arranged such that each co-planar waveguide flux qubit, of the multiple co-planar waveguide flux qubits, is operatively couplable to each other co-planar waveguide flux qubit, of the multiple co-planar waveguide flux qubits, of the quantum computing device, and a tuning quantum device, in which the tuning quantum device is in electrical contact with a first co-planar waveguide flux qubit of the plurality of co-planar waveguide flux qubits and with a second co-planar waveguide flux qubit of the plurality of co-planar waveguide flux qubits.