Materials and methods are disclosed for fabricating superconducting integrated circuits for quantum computing at millikelvin temperatures, comprising both quantum circuits and classical control circuits, which may be located on the same integrated circuit or on different chips of a multi-chip module. The materials may include components that reduce defect densities and increase quantum coherence times. Multilayer fabrication techniques provide low-power and a path to large scale computing systems. An integrated circuit system for quantum computing is provided, comprising: a substrate; a kinetic inductance layer having a kinetic inductance of at least 5 pH/square; a plurality of stacked planarized superconducting layers and intervening insulating layers, formed into a plurality of Josephson junctions having a critical current of less than 100 μA/μm.sup.2; and a resistive layer that remains non-superconducting at a temperature below 1 K, configured to damp the plurality of Josephson junctions.

A charging and field supplement circuit for superconducting magnets based on a pulsed current includes a capacitor charging circuit, an energy-storage capacitor, a capacitor discharging circuit, a superconducting magnetic energy storage circuit, and a superconducting persistent-current switch. Two output ends of the capacitor charging circuit are respectively connected to two ends of the energy-storage capacitor. Two input ends of the capacitor discharging circuit are respectively connected to the two ends of the energy-storage capacitor. Two output ends of the capacitor discharging circuit are respectively connected to two input ends of the superconducting magnetic energy storage circuit. Two output ends of the superconducting magnetic energy storage circuit are respectively connected to two input ends of the superconducting persistent-current switch. Two output ends of the superconducting persistent-current switch are configured to charge and magnetize a target superconducting magnet.

A charging and field supplement circuit for superconducting magnets based on a pulsed current includes a capacitor charging circuit, an energy-storage capacitor, a capacitor discharging circuit, a superconducting magnetic energy storage circuit, and a superconducting persistent-current switch. Two output ends of the capacitor charging circuit are respectively connected to two ends of the energy-storage capacitor. Two input ends of the capacitor discharging circuit are respectively connected to the two ends of the energy-storage capacitor. Two output ends of the capacitor discharging circuit are respectively connected to two input ends of the superconducting magnetic energy storage circuit. Two output ends of the superconducting magnetic energy storage circuit are respectively connected to two input ends of the superconducting persistent-current switch. Two output ends of the superconducting persistent-current switch are configured to charge and magnetize a target superconducting magnet.

Superconducting nanowire single photon detectors have recently been developed for a wide range of applications, including imaging and communications. An improved detection system is disclosed, whereby the detectors are monolithically integrated on the same chip with Josephson junctions for control and data processing. This enables an enhanced data rate, thereby facilitating several new and improved applications. A preferred embodiment comprises integrated digital processing based on single-flux-quantum pulses. An integrated multilayer fabrication method for manufacturing these integrated detectors is also disclosed. Preferred examples of systems comprising such integrated nanowire photon detectors include a time-correlated single photon counter, a quantum random number generator, an integrated single-photon imaging array, a sensitive digital communication receiver, and quantum-key distribution for a quantum communication system.

Superconducting nanowire single photon detectors have recently been developed for a wide range of applications, including imaging and communications. An improved detection system is disclosed, whereby the detectors are monolithically integrated on the same chip with Josephson junctions for control and data processing. This enables an enhanced data rate, thereby facilitating several new and improved applications. A preferred embodiment comprises integrated digital processing based on single-flux-quantum pulses. An integrated multilayer fabrication method for manufacturing these integrated detectors is also disclosed. Preferred examples of systems comprising such integrated nanowire photon detectors include a time-correlated single photon counter, a quantum random number generator, an integrated single-photon imaging array, a sensitive digital communication receiver, and quantum-key distribution for a quantum communication system.

A programmable circuit includes a superconducting component arranged in a multi-dimensional array of alternating narrow and wide portions. The programmable circuit further includes a plurality of heat sources, each heat source configured to selectively provide heat to a respective narrow portion sufficient to transition the respective narrow portion from a superconducting state to a non-superconducting state. The programmable circuit further includes a plurality of electrical terminals, each electrical terminal coupled to a respective wide portion of the multi-dimensional array.

A programmable circuit includes a superconducting component arranged in a multi-dimensional array of alternating narrow and wide portions. The programmable circuit further includes a plurality of heat sources, each heat source configured to selectively provide heat to a respective narrow portion sufficient to transition the respective narrow portion from a superconducting state to a non-superconducting state. The programmable circuit further includes a plurality of electrical terminals, each electrical terminal coupled to a respective wide portion of the multi-dimensional array.

A device includes a first semiconductor layer; a portion of a second semiconductor layer disposed on the first semiconductor layer; and a third semiconductor layer including a first region disposed on the portion of the second semiconductor layer and a second region disposed on the first semiconductor layer. A thickness of the first region is less than a predefined thickness. The device also includes an etch stop layer disposed on the third semiconductor layer; a plurality of distinct portions of a fourth semiconductor layer disposed on the etch stop layer and exposing one or more distinct portions of the etch stop layer over the portion of the second semiconductor layer; and a plurality of distinct portions of a superconducting layer disposed on the plurality of distinct portions of the fourth semiconductor layer and the exposed one or more distinct portions of the etch stop layer.

A memory cell having a Josephson junction and a magnetic junction situated in a close proximity to the Josephson junction. The two junctions may be vertically integrated. The magnetic junction has at least two magnetic layers with different coercive forces and a non-magnetic layer therebetween, to form a spin valve or pseudo-spin valve. A magnetization direction of a magnetic layer with lower coercive force can be rotated with respect to the larger coercive force magnetic layer(s). Magnetic fields produced by appropriately configured control lines carrying electric current, or spin-polarized current through the magnetic junction, can result in rotation. The magnetic junction influences the Josephson critical current of the Josephson junction, leading to distinct values of critical current which can serve as digital logic states. The so obtained memory cell can be integrated into the large arrays containing a plurality of the cells, to enable the selective READ and WRITE operations.

A memory cell having a Josephson junction and a magnetic junction situated in a close proximity to the Josephson junction. The two junctions may be vertically integrated. The magnetic junction has at least two magnetic layers with different coercive forces and a non-magnetic layer therebetween, to form a spin valve or pseudo-spin valve. A magnetization direction of a magnetic layer with lower coercive force can be rotated with respect to the larger coercive force magnetic layer(s). Magnetic fields produced by appropriately configured control lines carrying electric current, or spin-polarized current through the magnetic junction, can result in rotation. The magnetic junction influences the Josephson critical current of the Josephson junction, leading to distinct values of critical current which can serve as digital logic states. The so obtained memory cell can be integrated into the large arrays containing a plurality of the cells, to enable the selective READ and WRITE operations.