Northrop Grumman Systems Corporation

Joel D Strand

Anthony Joseph Przybysz

David George Ferguson

Zachary Keane

Ofer Naaman

Aurelius L Graninger

Micah John Atman Stoutimore

Zachary Kyle Keane

Aaron A Pesetski

Jeffrey David Hartman

Justin C Hackley

Robert L Miller

Ryan J Epstein

Andrew Hostetler Miklich

Gregory R Boyd

Kurt Pleim

Alexander Marakov

Mohamed Osama Abutaleb

David James Clarke

Cody James Ballard

Mohamed O Abutaleb

A superconducting AC switch system includes a switch network configuration comprising a Josephson junction (JJ) coupled to a transmission line having a transmission line impedance, and a magnetic field generator that is configured to switch from inducing a magnetic field in a plane of the JJ, and providing no magnetic field in the plane of the JJ. An AC input signal applied at an input of the switch network configuration is passed through to an output of the switch network configuration in a first magnetic state, and substantially reflected back to the input of the switch network configuration in a second magnetic state. The first magnetic state is one of inducing and not inducing a magnetic field in a plane of the JJ, and the second magnetic state is the other of inducing and not inducing a magnetic field in a plane of the JJ.

Superconducting AC switch system

Test structures and methods for superconducting bump bond electrical characterization are used to verify the superconductivity of bump bonds that electrically connect two superconducting integrated circuit chips fabricated using a flip-chip process, and can also ascertain the self-inductance of bump bond(s) between chips. The structures and methods leverage a behavioral property of superconducting DC SQUIDs to modulate a critical current upon injection of magnetic flux in the SQUID loop, which behavior is not present when the SQUID is not superconducting, by including bump bond(s) within the loop, which loop is split among chips. The sensitivity of the bump bond superconductivity verification is therefore effectively perfect, independent of any multi-milliohm noise floor that may exist in measurement equipment.

Superconducting bump bond electrical characterization

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.

Superconducting current control system

One example includes a flux switch system. The system includes an input stage configured to provide an interrogation pulse. The system also includes a plurality of flux loops configured to receive an input current. Each of the flux loops includes a Josephson junction configured to trigger to generate an output pulse in response to a first polarity of the input current and to not trigger to generate no output pulse in response to a second polarity of the input current opposite the first polarity. The system further includes an output stage configured to propagate the output pulse to an output of the flux switch system.

Flux switch system

Methods and apparatuses are provided for controlling the state of a qubit. A qubit apparatus includes a load, a qubit, and a compound Josephson junction coupler coupling the qubit to the load. A coupling controller controls the coupling strength of the compound Josephson junction coupler such that a coupling between the qubit and the load is a first value when a reset of the qubit is desired and a second value during operation of the qubit.

Controlling a state of a qubit assembly via tunable coupling

Systems and methods are provided for a ZZZ coupler. A first tunable coupler is coupled to the first qubit and tunable via a first control signal. A second tunable coupler is coupled to the first tunable coupler to direct a flux of the first qubit into a tuning loop of the second tunable coupler, such that when a first coupling strength associated with the first tunable coupler is non-zero, a second coupling strength, associated with the second tunable coupler, is a function of a second control signal applied to the second tunable coupler and a state of the first qubit. The second qubit and the third qubit are coupled to one another through the second tunable coupler, such that, when the second coupling strength is non-zero it is energetically favorable for the states of the first and second qubits to assume a specific relationship with respect to the Z-axis.

ZZZ coupler for superconducting qubits

A load-compensated tunable coupler leverages a cross-bar switch and simulated loads or ballasts to provide a tunable coupling between two quantum objects that can be selectively coupled or decoupled without changing their resonant frequencies.

Load-compensated tunable coupling

Systems and methods are provided for linking two components in a superconducting circuit. A plurality of circuit elements, each comprising one of an inductor, a capacitor, and a Josephson junction, are connected in series on a path connecting the two components. A plurality of tunable oscillators are connected from the path connecting the two components. Each tunable oscillator is responsive to a control signal to tune an associated resonance frequency of the tunable oscillator within a first frequency range, within which the two components are coupled, and within a second frequency range, within which the two components are isolated.

Robust tunable coupling between superconductive circuits

Systems and methods are provided for a tunable transmon qubit. The qubit includes a first Josephson junction on a first path between a transmission line and a circuit ground and second and third Josephson junctions arranged in parallel with one another on a second path between the transmission line and the circuit ground to form a direct current superconducting quantum interference device (DC SQUID). The DC SQUID is in parallel with the first Josephson junction. A capacitor is arranged in parallel with the first Josephson junction and the DC SQUID on a third path between the transmission line and the circuit ground as to form, in combination with the first path, an outer loop of the tunable transmon qubit. A bias circuit is configured to provide a constant bias flux to one of the DC SQUID and the outer loop of the tunable transmon qubit.

Tunable transmon circuit assembly

A superconducting system is provided that includes a coplanar superconducting circuit. The coplanar superconducting circuit includes a first ground plane region, a second ground plane region electrically isolated from the first ground plane region by portions of the coplanar superconducting circuit, and a tunable coupler having a first port and a second port. The tunable coupler comprises a variable inductance coupling element coupled between the first port and the second port, a first termination inductor having a first end coupled between a first end of the variable inductance element and a second end coupled to the first ground plane region, and a second termination inductor having a first end coupled between a second end of the variable inductance element and a second end coupled to the second ground plane region.

Superconducting tunable coupler

Quantum systems are provided, including a qubit and a transmission line resonator having an associated resonant wavelength. A coupling capacitor is configured to capacitively couple the qubit to the transmission line resonator. A transformer is configured to inductively couple the qubit to the transmission line resonator. A selected one of an associated capacitance of the coupling capacitor and an associated mutual inductance of the transformer is a function of a location of the qubit along the transmission line resonator.

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Ellicott City, MD, United States of America

Joel D Strand