Abstract: A superconductor system is provided that includes a superconductor device comprising a plurality of superconductor layers and dielectric layers interleaved with the plurality of superconductor layers, wherein at least one superconductor layer is a ground plane. The superconductor device further includes superconductor circuitry that resides within one or more of the plurality of superconductor layers, and one or more active moats extending through the plurality of superconductor layers and the dielectric layers, wherein at least one flux vortex caused by cryogenic cooling can be removed from at least one of the plurality of superconductor layers into the one or more active moats by the activating and deactivating of the one or more active moats.

Abstract: Systems and methods are provided for resetting a qubit comprising a superconducting loop and a compound Josephson junction. A first bias flux is provided to the superconducting loop. A second bias flux is provided to the compound Josephson junction. Each of the first bias flux and the second bias flux are provided such that a given excited state of the qubit is near a top of a potential barrier associated with a potential of the qubit. A continuous microwave signal is generated having a frequency equal to a transition frequency between an other excited state of the qubit and the given excited state.

Abstract: 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.

Abstract: 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.

Abstract: One example includes a current device readout system. The system includes a tunable resonator having a resonant frequency that is associated with a current state of a current device. The tunable resonator can be configured to receive a tone signal having a predetermined frequency from a feedline to determine the current state of the current device. The system also includes an isolation device inductively interconnecting the tunable resonator and the current device. The isolation device can be tunable to isolate the current device in a first state and to facilitate the determination of the current state of the current device in a second state.

Abstract: 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.

Abstract: One example includes a current device readout system. The system includes a tunable resonator having a resonant frequency that is associated with a current state of a current device. The tunable resonator can be configured to receive a tone signal having a predetermined frequency from a feedline to determine the current state of the current device. The system also includes an isolation device inductively interconnecting the tunable resonator and the current device. The isolation device can be tunable to isolate the current device in a first state and to facilitate the determination of the current state of the current device in a second state.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Systems and methods are provided for readout of a qubit. A readout resonator is coupled to a transmission line and a compound Josephson junction coupler couples the qubit to the readout resonator. A coupling controller controls the coupling strength of the compound Josephson junction coupler such that a coupling between the qubit and the readout resonator is a first value when a state of the qubit is being read and a second value during operation of the qubit.

Abstract: One example includes a flux qubit readout circuit. The circuit includes a gradiometric SQUID that is configured to inductively couple with a gradiometric flux qubit to modify flux associated with the gradiometric superconducting quantum interference device (SQUID) based on a flux state of the flux qubit. The circuit also includes a current source configured to provide a readout current through the gradiometric SQUID during a state readout operation to determine the flux state of the gradiometric flux qubit at a readout node.

Abstract: Systems and methods are provided for readout of a qubit. A readout resonator is coupled to a transmission line and a compound Josephson junction coupler couples the qubit to the readout resonator. A coupling controller controls the coupling strength of the compound Josephson junction coupler such that a coupling between the qubit and the readout resonator is a first value when a state of the qubit is being read and a second value during operation of the qubit.

Abstract: One example includes a flux qubit readout circuit. The circuit includes a gradiometric SQUID that is configured to inductively couple with a gradiometric flux qubit to modify flux associated with the gradiometric superconducting quantum interference device (SQUID) based on a flux state of the flux qubit. The circuit also includes a current source configured to provide a readout current through the gradiometric SQUID during a state readout operation to determine the flux state of the gradiometric flux qubit at a readout node.

Abstract: 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.

Abstract: 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.

Abstract: 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.