Abstract: Analog processors for solving various computational problems are provided. Such analog processors comprise a plurality of quantum devices, arranged in a lattice, together with a plurality of coupling devices. The analog processors further comprise bias control systems each configured to apply a local effective bias on a corresponding quantum device. A set of coupling devices in the plurality of coupling devices is configured to couple nearest-neighbor quantum devices in the lattice. Another set of coupling devices is configured to couple next-nearest neighbor quantum devices. The analog processors further comprise a plurality of coupling control systems each configured to tune the coupling value of a corresponding coupling device in the plurality of coupling devices to a coupling. Such quantum processors further comprise a set of readout devices each configured to measure the information from a corresponding quantum device in the plurality of quantum devices.

Abstract: Analog processors for solving various computational problems are provided. Such analog processors comprise a plurality of quantum devices, arranged in a lattice, together with a plurality of coupling devices. The analog processors further comprise bias control systems each configured to apply a local effective bias on a corresponding quantum device. A set of coupling devices in the plurality of coupling devices is configured to couple nearest-neighbor quantum devices in the lattice. Another set of coupling devices is configured to couple next-nearest neighbor quantum devices. The analog processors further comprise a plurality of coupling control systems each configured to tune the coupling value of a corresponding coupling device in the plurality of coupling devices to a coupling. Such quantum processors further comprise a set of readout devices each configured to measure the information from a corresponding quantum device in the plurality of quantum devices.

Abstract: Analog processors for solving various computational problems are provided. Such analog processors comprise a plurality of quantum devices, arranged in a lattice, together with a plurality of coupling devices. The analog processors further comprise bias control systems each configured to apply a local effective bias on a corresponding quantum device. A set of coupling devices in the plurality of coupling devices is configured to couple nearest-neighbor quantum devices in the lattice. Another set of coupling devices is configured to couple next-nearest neighbor quantum devices. The analog processors further comprise a plurality of coupling control systems each configured to tune the coupling value of a corresponding coupling device in the plurality of coupling devices to a coupling. Such quantum processors further comprise a set of readout devices each configured to measure the information from a corresponding quantum device in the plurality of quantum devices.

Abstract: Analog processors for solving various computational problems are provided. Such analog processors comprise a plurality of quantum devices, arranged in a lattice, together with a plurality of coupling devices. The analog processors further comprise bias control systems each configured to apply a local effective bias on a corresponding quantum device. A set of coupling devices in the plurality of coupling devices is configured to couple nearest-neighbor quantum devices in the lattice. Another set of coupling devices is configured to couple next-nearest neighbor quantum devices. The analog processors further comprise a plurality of coupling control systems each configured to tune the coupling value of a corresponding coupling device in the plurality of coupling devices to a coupling. Such quantum processors further comprise a set of readout devices each configured to measure the information from a corresponding quantum device in the plurality of quantum devices.

Abstract: Analog processors for solving various computational problems are provided. Such analog processors comprise a plurality of quantum devices, arranged in a lattice, together with a plurality of coupling devices. The analog processors further comprise bias control systems each configured to apply a local effective bias on a corresponding quantum device. A set of coupling devices in the plurality of coupling devices is configured to couple nearest-neighbor quantum devices in the lattice. Another set of coupling devices is configured to couple next-nearest neighbor quantum devices. The analog processors further comprise a plurality of coupling control systems each configured to tune the coupling value of a corresponding coupling device in the plurality of coupling devices to a coupling. Such quantum processors further comprise a set of readout devices each configured to measure the information from a corresponding quantum device in the plurality of quantum devices.

Abstract: A method for computing using a quantum system comprising a plurality of superconducting qubits is provided. Quantum system can be in any one of at least two configurations including (i) an initialization Hamiltonian H0 and (ii) a problem Hamiltonian HP. The plurality of superconducting qubits are arranged with respect to one another, with a predetermined number of couplings between respective pairs of superconducting qubits in the plurality of qubits, such that the plurality of superconducting qubits, coupled by the predetermined number of couplings, collectively define a computational problem to be solved. In the method, quantum system is initialized to the initialization Hamiltonian HO. Quantum system is then adiabatically changed until it is described by the ground state of the problem Hamiltonian HP. The quantum state of quantum system is then readout thereby solving the computational problem to be solved.

Abstract: A method for computing using a quantum system comprising a plurality of superconducting qubits is provided. Quantum system can be in any one of at least two configurations including (i) an initialization Hamiltonian H0 and (ii) a problem Hamiltonian HP. The plurality of superconducting qubits are arranged with respect to one another, with a predetermined number of couplings between respective pairs of superconducting qubits in the plurality of qubits, such that the plurality of superconducting qubits, coupled by the predetermined number of couplings, collectively define a computational problem to be solved. In the method, quantum system is initialized to the initialization Hamiltonian HO. Quantum system is then adiabatically changed until it is described by the ground state of the problem Hamiltonian HP. The quantum state of quantum system is then readout thereby solving the computational problem to be solved.

Abstract: The present invention involves a quantum computing apparatus that includes a substrate attached to which is a flux shield upon which is at least one element of circuitry. The flux shield has an aperture. Inside the aperture is a superconducting structure. The superconducting structure and the circuitry interact so that a change in a state of the superconducting structure can be detected by the circuitry. The present invention provides a method for initializing and measuring the state of a superconducting structure by adjusting and measuring the current in an element of circuitry coupled to the structure by a flux shield. The present invention provides a mechanism for coupling qubits. In embodiments of the present invention, qubits are selectively coupled by a coupling circuit that can be on a second substrate. The coupling of the qubit to the coupling circuit is enhanced by the presence of a flux shield.

Abstract: A structure comprising a tank circuit inductively coupled to a flux qubit or a phase qubit. In some embodiments, a low temperature preamplifier is in electrical communication with the tank circuit. The tank circuit comprises an effective capacitance and an effective inductance that are in parallel or in series. In some embodiments, the effective inductance comprises a multiple winding coil of wire. A method that includes the steps of (i) providing a tank circuit and a phase qubit that are inductively coupled, (ii) reading out a state of the phase qubit, (iii) applying a flux to the phase qubit that approaches a net zero flux, (iv) increasing a level of flux applied to the phase qubit, and (v) observing a response of the tank circuit in a readout device.

Abstract: A method for quantum computing with a quantum system comprising a first energy level, a second energy level, and a third energy level. The first energy level and said second energy level are capable of being degenerate with respect to each other. In the method a signal is applied to the quantum system. The signal has an alternating amplitude at an associated frequency such that (i) the frequency of the signal correlates with an energy level separation between the first energy level and the third energy level or (ii) the frequency of the signal correlates with an energy level separation between the second energy level and the third energy level. The signal induces an oscillation in the state of the quantum system between the first energy level and the second energy level.

Abstract: The present invention generally involves an extra-substrate control system comprising a first substrate, attached to which is at least one superconducting structure, and a second substrate, connected to which is at least one element of circuitry, wherein the superconducting structure and the circuitry interact, so that a change in a state of the superconducting structure can be detected by the circuitry. The present invention also provides a quantum computing apparatus comprising a first substrate, attached to which is one or more layers of material, at least one of which is a superconducting material, a second substrate, deposited on which is a flux shield and on the flux shield is at least one element of circuitry, wherein the superconducting material and the second substrate are separated by a mean distance that is small enough to permit coupling between the element of circuitry and the superconducting material.

Abstract: A method for quantum computing with a quantum system comprising a first energy level, a second energy level, and a third energy level. The first energy level and said second energy level are capable of being degenerate with respect to each other. In the method a signal is applied to the quantum system. The signal has an alternating amplitude at an associated frequency such that (i) the frequency of the signal correlates with an energy level separation between the first energy level and the third energy level or (ii) the frequency of the signal correlates with an energy level separation between the second energy level and the third energy level. The signal induces an oscillation in the state of the quantum system between the first energy level and the second energy level.

Abstract: The present invention generally involves an extra-substrate control system comprising a first substrate, attached to which is at least one superconducting structure, and a second substrate, connected to which is at least one element of circuitry, wherein the superconducting structure and the circuitry interact, so that a change in a state of the superconducting structure can be detected by the circuitry. The present invention also provides a quantum computing apparatus comprising a first substrate, attached to which is one or more layers of material, at least one of which is a superconducting material, a second substrate, deposited on which is a flux shield and on the flux shield is at least one element of circuitry, wherein the superconducting material and the second substrate are separated by a mean distance that is small enough to permit coupling between the element of circuitry and the superconducting material.

Abstract: The present invention comprises a junction between an unconventional superconductor, an intermediate material, and a conventional superconducting material. In some embodiments, the unconventional superconductor has an orthorhombic crystal structure and the supercurrent in the resulting junction flows in the c-axis direction of the orthorhombic crystal. In other embodiments, the supercurrent flows parallel to a direction in the a-b plane. Interface junctions according to embodiments of the present invention may be used in superconducting low inductance qubits (SLIQs) and in permanent readout superconducting qubits (PRSQs), can form the basis of quantum registers, and can permit parity keys or other devices made from conventional superconducting material to be attached to qubits made from unconventional superconducting material or vice versa.

Abstract: A structure comprising a tank circuit inductively coupled to a flux qubit or a phase qubit. In some embodiments, a low temperature preamplifier is in electrical communication with the tank circuit. The tank circuit comprises an effective capacitance and an effective inductance that are in parallel or in series. In some embodiments, the effective inductance comprises a multiple winding coil of wire. A method that includes the steps of (i) providing a tank circuit and a phase qubit that are inductively coupled, (ii) reading out a state of the phase qubit, (iii) applying a flux to the phase qubit that approaches a net zero flux, (iv) increasing a level of flux applied to the phase qubit, and (v) observing a response of the tank circuit in a readout device.

Abstract: The present invention generally involves an extra-substrate control system comprising a first substrate, attached to which is at least one superconducting structure, and a second substrate, connected to which is at least one element of circuitry, wherein the superconducting structure and the circuitry interact, so that a change in a state of the superconducting structure can be detected by the circuitry. The present invention also provides a quantum computing apparatus comprising a first substrate, attached to which is one or more layers of material, at least one of which is a superconducting material, a second substrate, deposited on which is a flux shield and on the flux shield is at least one element of circuitry, wherein the superconducting material and the second substrate are separated by a mean distance that is small enough to permit coupling between the element of circuitry and the superconducting material.

Abstract: In accordance with embodiments of the present invention, a junction of an unconventional superconductor, an intermediate material, and a conventional superconducting material is presented. In some embodiments, the resulting junction is in the c-axis direction of the orthorhombic unconventional superconductor. Alternatively, the junction is in the a-b plane direction. Interface junctions according to embodiments of the present invention may be used in super low inductance qubits (SLIQs) and in permanent readout superconducting qubits (PRSQs), can form the basis of quantum registers, and can allow for parity keys or other devices made from conventional superconducting material to be attached to qubits made from unconventional superconducting material or vice versa. Coherent tunnel junctions according to embodiments of the present invention may be used to form parity keys or coherently couple two regions of a superconducting material.

Abstract: A method of forming a grain boundary Josephson junction includes forming a superconducting layer on a substrate, patterning the superconducting layer to form the grain boundary Josephson junction, and annealing the substrate and superconducting layer in oxygen in order to increase the critical current density of the junction. The method is applicable to various types of junctions, including DD, DND, and SND junctions formed on various types of substrates, including bi-crystal substrates and single crystal substrates. The annealing is reversible. Oxygen can be removed from the junction, thereby decreasing the critical current density of the junction. In some instances, after patterning, the superconducting layer has a dimension smaller than a length of a facet in the superconducting layer.

Abstract: The present invention comprises a junction between an unconventional superconductor, an intermediate material, and a conventional superconducting material. In some embodiments, the unconventional superconductor has an orthorhombic crystal structure and the supercurrent in the resulting junction flows in the c-axis direction of the orthorhombic crystal. In other embodiments, the supercurrent flows parallel to a direction in the a-b plane. Interface junctions according to embodiments of the present invention may be used in superconducting low inductance qubits (SLIQs) and in permanent readout superconducting qubits (PRSQs), can form the basis of quantum registers, and can permit parity keys or other devices made from conventional superconducting material to be attached to qubits made from unconventional superconducting material or vice versa.