Abstract: A system and method are disclosed for a superconducting traveling-wave parametric amplifier (TWPA) with improved control and performance. In a preferred embodiment, the amplifier comprises an integrated array of symmetric rf-SQUIDs in a transmission line structure. A device was fabricated using niobium superconducting integrated circuits, and confirmed predicted performance, with a maximum gain up to 17 dB and a bandwidth of 4 GHz. A similar device can be applied as a low-noise, low-dissipation microwave amplifier for output from a superconducting quantum computer, or as a preamplifier, switch, or frequency converter for a sensitive microwave receiver, or as an output amplifier for a frequency-multiplexed superconducting detector array.

Abstract: A system and method to convert a wideband optical signal to a multi-bit digital electrical signal using a superconducting integrated circuit. In a preferred embodiment, the optical signal modulates the phase (i.e., adjusts the timing) of a sequence of single-flux-quantum voltage pulses. The optoelectronic modulator may comprise an optically tunable Josephson junction, superconducting inductor, or bolometric detector, with switching speeds approaching 100 ps or less. The optical signal may comprise a plurality of optical signals such as a wavelength-division multiplexed signal. The optical-to-digital converter may be applied to high-speed digital communication switches, broadband digital input/output for superconducting or quantum computing, and control/readout of detector arrays.

Abstract: A superconducting memory cell includes a magnetic Josephson junction (MJJ) with a ferromagnetic material, having at least two switchable states of magnetization. The binary state of the MJJ manifests itself as a pulse appearing, or not appearing, on the output. A superconducting memory includes an array of memory cells. Each memory cell includes a comparator with at least one MJJ. Selected X and Y-directional write lines in their combination are capable of switching the magnetization of the MJJ. A superconducting device includes a first and a second junction in a stacked configuration. The first junction has an insulating layer barrier, and the second junction has an insulating layer sandwiched in-between two ferromagnetic layers as barrier. An electrical signal inputted across the first junction is amplified across the second junction.

Abstract: 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.

Abstract: 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.

Abstract: A system and method for high-speed, low-power cryogenic computing are presented, comprising ultrafast energy-efficient RSFQ superconducting computing circuits, and hybrid magnetic/superconducting memory arrays and interface circuits, operating together in the same cryogenic environment. An arithmetic logic unit and register file with an ultrafast asynchronous wave-pipelined datapath is also provided. The superconducting circuits may comprise inductive elements fabricated using both a high-inductance layer and a low-inductance layer. The memory cells may comprise superconducting tunnel junctions that incorporate magnetic layers. Alternatively, the memory cells may comprise superconducting spin transfer magnetic devices (such as orthogonal spin transfer and spin-Hall effect devices). Together, these technologies may enable the production of an advanced superconducting computer that operates at clock speeds up to 100 GHz.

Abstract: A method for bonding two superconducting integrated circuits (“chips”), such that the bonds electrically interconnect the chips. A plurality of indium-coated metallic posts may be deposited on each chip. The indium bumps are aligned and compressed with moderate pressure at a temperature at which the indium is deformable but not molten, forming fully superconducting connections between the two chips when the indium is cooled down to the superconducting state. An anti-diffusion layer may be applied below the indium bumps to block reaction with underlying layers. The method is scalable to a large number of small contacts on the wafer scale, and may be used to manufacture a multi-chip module comprising a plurality of chips on a common carrier. Superconducting classical and quantum computers and superconducting sensor arrays may be packaged.

Abstract: A cryogenic optoelectronic data link, comprising a sending module operating at a cryogenic temperature less than 100 K. An ultrasensitive electro-optic modulator, sensitive to input voltages of less than 10 mV, may include at least one optically active layer of graphene, which may be part of a microscale resonator, which in turn may be integrated with an optical waveguide or an optical fiber. The optoelectronic data link enables optical output of weak electrical signals from superconducting or other cryogenic electronic devices in either digital or analog form. The modulator may be integrated on the same chip as the cryogenic electrical devices. A plurality of cryogenic electrical devices may generate a plurality of electrical signals, each coupled to its own modulator. The plurality of modulators may be resonant at different frequencies, and coupled to a common optical output line to transmit a combined wavelength-division-multiplexed (WDM) optical signal.

Abstract: 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 ?A/?m2; and a resistive layer that remains non-superconducting at a temperature below 1 K, configured to damp the plurality of Josephson junctions.

Abstract: A system and method for high-speed, low-power cryogenic computing are presented, comprising ultrafast energy-efficient RSFQ superconducting computing circuits, and hybrid magnetic/superconducting memory arrays and interface circuits, operating together in the same cryogenic environment. An arithmetic logic unit and register file with an ultrafast asynchronous wave-pipelined datapath is also provided. The superconducting circuits may comprise inductive elements fabricated using both a high-inductance layer and a low-inductance layer. The memory cells may comprise superconducting tunnel junctions that incorporate magnetic layers. Alternatively, the memory cells may comprise superconducting spin transfer magnetic devices (such as orthogonal spin transfer and spin-Hall effect devices). Together, these technologies may enable the production of an advanced superconducting computer that operates at clock speeds up to 100 GHz.

Abstract: 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.

Abstract: A system and method to convert a wideband optical signal to a multi-bit digital electrical signal using a superconducting integrated circuit. In a preferred embodiment, the optical signal modulates the phase (i.e., adjusts the timing) of a sequence of single-flux-quantum voltage pulses. The optoelectronic modulator may comprise an optically tunable Josephson junction, superconducting inductor, or bolometric detector, with switching speeds approaching 100 ps or less. The optical signal may comprise a plurality of optical signals such as a wavelength-division multiplexed signal. The optical-to-digital converter may be applied to high-speed digital communication switches, broadband digital input/output for superconducting or quantum computing, and control/readout of detector arrays.

Abstract: A superconducting memory cell includes a magnetic Josephson junction (MJJ) with a ferromagnetic material, having at least two switchable states of magnetization. The binary state of the MJJ manifests itself as a pulse appearing, or not appearing, on the output. A superconducting memory includes an array of memory cells. Each memory cell includes a comparator with at least one MJJ. Selected X and Y-directional write lines in their combination are capable of switching the magnetization of the MJJ. A superconducting device includes a first and a second junction in a stacked configuration. The first junction has an insulating layer barrier, and the second junction has an insulating layer sandwiched in-between two ferromagnetic layers as barrier. An electrical signal inputted across the first junction is amplified across the second junction.

Abstract: A cryogenic optoelectronic data link, comprising a sending module operating at a cryogenic temperature less than 100 K. An ultrasensitive electro-optic modulator, sensitive to input voltages of less than 10 mV, may include at least one optically active layer of graphene, which may be part of a microscale resonator, which in turn may be integrated with an optical waveguide or an optical fiber. The optoelectronic data link enables optical output of weak electrical signals from superconducting or other cryogenic electronic devices in either digital or analog form. The modulator may be integrated on the same chip as the cryogenic electrical devices. A plurality of cryogenic electrical devices may generate a plurality of electrical signals, each coupled to its own modulator. The plurality of modulators may be resonant at different frequencies, and coupled to a common optical output line to transmit a combined wavelength-division-multiplexed (WDM) optical signal.

Abstract: A superconducting quantum interference devices (SQUID) comprises a superconducting inductive loop with at least two Josephson junction, whereby a magnetic flux coupled into the inductive loop produces a modulated response up through radio frequencies. Series and parallel arrays of SQUIDs can increase the dynamic range, output, and linearity, while maintaining bandwidth. Several approaches to achieving a linear triangle-wave transfer function are presented, including harmonic superposition of SQUID cells, differential serial arrays with magnetic frustration, and a novel bi-SQUID cell comprised of a nonlinear Josephson inductance shunting the linear coupling inductance. Total harmonic distortion of less than ?120 dB can be achieved in optimum cases.

Abstract: A system and method for high-speed, low-power cryogenic computing are presented, comprising ultrafast energy-efficient RSFQ superconducting computing circuits, and hybrid magnetic/superconducting memory arrays and interface circuits, operating together in the same cryogenic environment. An arithmetic logic unit and register file with an ultrafast asynchronous wave-pipelined datapath is also provided. The superconducting circuits may comprise inductive elements fabricated using both a high-inductance layer and a low-inductance layer. The memory cells may comprise superconducting tunnel junctions that incorporate magnetic layers. Alternatively, the memory cells may comprise superconducting spin transfer magnetic devices (such as orthogonal spin transfer and spin-Hall effect devices). Together, these technologies may enable the production of an advanced superconducting computer that operates at clock speeds up to 100 GHz.

Abstract: A superconducting integrated circuit, comprising a plurality of superconducting circuit elements, each having a variation in operating voltage over time; a common power line; and a plurality of bias circuits, each connected to the common power line, and to a respective superconducting circuit element, wherein each respective bias circuit is superconducting during at least one time portion of the operation of a respective superconducting circuit element, and is configured to supply the variation in operating voltage over time to the respective superconducting circuit element.

Abstract: Superconducting integrated circuits require several wiring layers to distribute bias and signals across the circuit, which must cross each other both with and without contacts. All wiring lines and contacts must be fully superconducting, and in the prior art each wiring layer comprises a single metallic thin film. An alternative wiring layer is disclosed that comprises sequential layers of two or more different metals. Such a multi-metallic wiring layer may offer improved resistance to impurity diffusion, better surface passivation, and/or reduction of stress, beyond that which is attainable with a single-metallic wiring layer. The resulting process leads to improved margin and yield in an integrated circuit comprising a plurality of Josephson junctions. Several preferred embodiments are disclosed, for both planarized and non-planarized processes.

Abstract: A superconducting memory cell includes a magnetic Josephson junction (MJJ) with a ferromagnetic material, having at least two switchable states of magnetization. The binary state of the MJJ manifests itself as a pulse appearing, or not appearing, on the output. A superconducting memory includes an array of memory cells. Each memory cell includes a comparator with at least one MJJ. Selected X and Y-directional write lines in their combination are capable of switching the magnetization of the MJJ. A superconducting device includes a first and a second junction in a stacked configuration. The first junction has an insulating layer barrier, and the second junction has an insulating layer sandwiched in-between two ferromagnetic layers as barrier. An electrical signal inputted across the first junction is amplified across the second junction.

Abstract: A system and method to convert a wideband optical signal to a multi-bit digital electrical signal using a superconducting integrated circuit. In a preferred embodiment, the optical signal modulates the phase (i.e., adjusts the timing) of a sequence of single-flux-quantum voltage pulses. The optoelectronic modulator may comprise an optically tunable Josephson junction, superconducting inductor, or bolometric detector, with switching speeds approaching 100 ps or less. The optical signal may comprise a plurality of optical signals such as a wavelength-division multiplexed signal. The optical-to-digital converter may be applied to high-speed digital communication switches, broadband digital input/output for superconducting or quantum computing, and control/readout of detector arrays.