Abstract: 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.

Abstract: A capacitively-driven tunable coupler includes a coupling capacitor connecting an open end of a quantum object (i.e., an end of the object that cannot have a DC path to a low-voltage rail, such as a ground node, without breaking the functionality of the object) to an RF SQUID having a Josephson element capable of providing variable inductance and therefore variable coupling to another quantum object.

Abstract: A capacitively-driven tunable coupler includes a coupling capacitor connecting an open end of a quantum object (i.e., an end of the object that cannot have a DC path to a low-voltage rail, such as a ground node, without breaking the functionality of the object) to an RF SQUID having a Josephson element capable of providing variable inductance and therefore variable coupling to another quantum object.

Abstract: A capacitively-driven tunable coupler includes a coupling capacitor connecting an open end of a quantum object (i.e., an end of the object that cannot have a DC path to a low-voltage rail, such as a ground node, without breaking the functionality of the object) to an RF SQUID having a Josephson element capable of providing variable inductance and therefore variable coupling to another quantum object.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Real-time reconfigurability of quantum object connectivity can be provided with one or more quantum routers that can each be configured as either or both of a single-pole double-throw switch and a cross-point switch. The quantum router includes variable-inductance coupling elements in RF-SQUIDs having inductors transformer-coupled to two control flux lines, one providing a static current and the other providing a dynamic current, the direction of which can be toggled to couple or uncouple quantum objects, such as qubits, based on the dynamic current direction to provide reconfigurable quantum routing.

Abstract: Real-time reconfigurability of quantum object connectivity can be provided with one or more quantum routers that can each be configured as either or both of a single-pole double-throw switch and a cross-point switch. The quantum router includes variable-inductance coupling elements in RF-SQUIDs having inductors transformer-coupled to two control flux lines, one providing a static current and the other providing a dynamic current, the direction of which can be toggled to couple or uncouple quantum objects, such as qubits, based on the dynamic current direction to provide reconfigurable quantum routing.

Abstract: A tunable bus-mediated coupling system is provided that includes a first input port coupled to a first end of a variable inductance coupling element through a first resonator and a second input port coupled to a second end of the variable inductance coupling element through a second resonator. The first input port is configured to be coupled to a first qubit, and the second output port is configured to be coupled to a second qubit. A controller is configured to control the inductance of the variable inductance coupling element between a low inductance state to provide strong coupling between the first qubit and the second qubit and a high inductance state to provide isolation between the first qubit and the second qubit.

Abstract: A capacitively-driven tunable coupler includes a coupling capacitor connecting an open end of a quantum object (i.e., an end of the object that cannot have a DC path to a low-voltage rail, such as a ground node, without breaking the functionality of the object) to an RF SQUID having a Josephson element capable of providing variable inductance and therefore variable coupling to another quantum object.

Abstract: 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.

Abstract: A push-pull tunable coupler includes a push transformer, a pull transformer and two compound Josephson junctions arranged in upper and lower branches. Absent biasing, the balanced push and pull of current between the branches causes current from a first object to circulate within a loop and not to be coupled to a second object. Biasing of at least one of the compound Josephson junctions unbalances the push and pull of current in the branches to couple the first and second objects. The coupler has reduced sensitivity to differential-mode noise around the off state, is completely insensitive to common-mode noise, and is capable of inverting the coupled signal with appropriate relative biasing of the compound Josephson junctions.

Abstract: A tunable bus-mediated coupling system is provided that includes a first input port coupled to a first end of a variable inductance coupling element through a first resonator and a second input port coupled to a second end of the variable inductance coupling element through a second resonator. The first input port is configured to be coupled to a first qubit, and the second output port is configured to be coupled to a second qubit. A controller is configured to control the inductance of the variable inductance coupling element between a low inductance state to provide strong coupling between the first qubit and the second qubit and a high inductance state to provide isolation between the first qubit and the second qubit.

Abstract: A tunable bus-mediated coupling system is provided that includes a first input port coupled to a first end of a variable inductance coupling element through a first resonator and a second input port coupled to a second end of the variable inductance coupling element through a second resonator. The first input port is configured to be coupled to a first qubit, and the second output port is configured to be coupled to a second qubit. A controller is configured to control the inductance of the variable inductance coupling element between a low inductance state to provide strong coupling between the first qubit and the second qubit and a high inductance state to provide isolation between the first qubit and the second qubit.

Abstract: A tunable bus-mediated coupling system is provided that includes a first input port coupled to a first end of a variable inductance coupling element through a first resonator and a second input port coupled to a second end of the variable inductance coupling element through a second resonator. The first input port is configured to be coupled to a first qubit, and the second output port is configured to be coupled to a second qubit. A controller is configured to control the inductance of the variable inductance coupling element between a low inductance state to provide strong coupling between the first qubit and the second qubit and a high inductance state to provide isolation between the first qubit and the second qubit.

Abstract: 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.

Abstract: 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.

Abstract: A method for producing planar extended electrodes with nanoscale spacings that exhibit very large SERS signals, with each nanoscale gap having one well-defined hot spot. The resulting highly sensitive substrate has extended metal electrodes separated by a nanoscale gap. The electrodes act as optical antennas to enhance dramatically the local electromagnetic field for purposes of spectroscopy or nonlinear optics. SERS response is consistent with a very small number of molecules in the hotspot, showing blinking and wandering of Raman lines. Sensitivity is sufficiently high that SERS from physisorbed atmospheric contaminants may be detected after minutes of exposure to ambient conditions.

Abstract: A method for producing planar extended electrodes with nanoscale spacings that exhibit very large SERS signals, with each nanoscale gap having one well-defined hot spot. The resulting highly sensitive substrate has extended metal electrodes separated by a nanoscale gap. The electrodes act as optical antennas to enhance dramatically the local electromagnetic field for purposes of spectroscopy or nonlinear optics. SERS response is consistent with a very small number of molecules in the hotspot, showing blinking and wandering of Raman lines. Sensitivity is sufficiently high that SERS from physisorbed atmospheric contaminants may be detected after minutes of exposure to ambient conditions.