Abstract: A superconducting structure that can operate, for example, as a qubit or a superconducting switch is presented. The structure includes a loop formed from two parts. A first part includes two superconducting materials separated by a junction. The junction can, for example, be a 45° grain boundary junction. The second part can couple the two superconducting materials across the junction. The second part includes a superconducting material coupled to each of the two superconducting materials of the first part through c-axis junctions. Further embodiments of the invention can be as a coherent unconventional superconducting switch, or a variable phase shift unconventional superconductor junction device.

Abstract: A method for fabricating a closed-form Josephson junction includes etching the inner shape of the closed-form junction on the chip, depositing a negative photoresist material over the etched chip, and flood exposing the backside of the chip with ultraviolet radiation. The photoresist is developed and then baked onto the chip. The baked photoresist serves as a mask for subsequent etching of the exterior of the closed-form Josephson junction. A shaped Josephson junction is fabricated with junction widths between about 0.1 &mgr;m and about 1 &mgr;m and an inner diameter ranging between about 1 &mgr;m and about 1000 &mgr;m.

Abstract: An optical device having an optical microsphere. Resonant electromagnetic radiation is trapped in the microsphere and manipulated with externally applied electric and magnetic fields to control polarization components of the excited energy within the microsphere. The optical microsphere can be used as a signal inverter. In the single photon regime, the optical microsphere can be used as a mechanism for entangling qubit states coded by the polarization states of whispering gallery modes excited in the microsphere. Furthermore, the device can be used as a switch for the absorption or reflection of photons in response to control photons.

Abstract: Quantum computing systems and methods that use opposite magnetic moment states read the state of a qubit by applying current through the qubit and measuring a Hall effect voltage across the width of the current. For reading, the qubit is grounded to freeze the magnetic moment state, and the applied current is limited to pulses incapable of flipping the magnetic moment. Measurement of the Hall effect voltage can be achieved with an electrode system that is capacitively coupled to the qubit. An insulator or tunnel barrier isolates the electrode system from the qubit during quantum computing. The electrode system can include a pair of electrodes for each qubit. A readout control system uses a voltmeter or other measurement device that connects to the electrode system, a current source, and grounding circuits. For a multi-qubit system, selection logic can select which qubit or qubits are read.

Abstract: A method is described for forming a solid state qubit. The method includes forming a dot or an anti-dot. The dot or anti-dot can be formed on a substrate and is delimited by an interface that defines a closed area. The dot or anti-dot includes a superconductive material with Cooper pairs that are in a state of non-zero orbital angular momentum on at least one side of the interface. The method includes removing superconducting material on the inner side of the interface or removing the outer side of the interface by etching. The method can further include forming a dot or an anti-dot by damaging the superconducting material such that the superconductive material becomes non-superconductive in predefined areas. The damaging of superconducting material can be performed by irradiation with particles, such as alpha particles or neutrons. The superconductive material can also be formed by doping a non-superconductive material.

Abstract: A solid state dc-SQUID includes a superconducting loop containing a plurality of Josephson junctions, wherein an intrinsic phase shift is accumulated through the loop. In an embodiment of the invention, the current-phase response of the dc-SQUID sits in a linear regime where directional sensitivity to flux through the loop occurs. Changes in the flux passing through the superconducting loop stimulates current which can be quantified, thus providing a means of measuring the magnetic field. Given the linear and directional response regime of the embodied device, an inherent current to phase sensitivity is achieved that would otherwise be unobtainable in common dc-SQUID devices without extrinsic intervention.

Abstract: In accordance with the present invention, a superconducting phase shift device is presented. The phase shift device can introduce a phase shift between the phases of the order parameters of the device's two terminals. The two terminals can be coupled through an anisotropic superconductor with angled sides, or through two anisotropic superconductors with misaligned phases, or through a ferromagnet in the junction area. The phase shift device can be used in superconducting quantum computing circuitry. A method of fabricating the phase shift device with a technology different from fabrication technology of conventional superconducting materials is described. A method for fabricating a phase shifter chip including an array of phase shift devices is described.

Abstract: An optical transformer having an optical microsphere is disclosed. Resonant electromagnetic radiation can be trapped in the microsphere and can be manipulated with externally applied electric and magnetic fields to manipulate polarization components of the excited energy. In some embodiments, the resonant modes of the microsphere can be excited from optical fibers. Transitions between modes of the electromagnetic radiation trapped in the microsphere can be accomplished, providing mechanisms for manipulating excited energy in the microsphere. In the single photon regime, the disclosed optical transformer can be used as a quantum bit for application of quantum algorithms.

Abstract: A solid-state quantum computing structure includes a dot of superconductive material, where the superconductor possesses a dominant order parameter with a non-zero angular momentum and a sub-dominant order parameter that can have any pairing symmetry. Alternately a solid-state quantum computing structure includes an anti-dot, which is a region in a superconductor where the order parameter is suppressed. In either embodiment of the invention, circulating persistent currents are generated via time-reversal symmetry breaking effects in the boundaries between superconducting and insulating materials. These effects cause the ground state for the supercurrent circulating near the qubit to be doubly degenerate, with two supercurrent ground states having distinct magnetic moments. These quantum states of the supercurrents store quantum information, which creates the basis of qubits for quantum computing.

Abstract: A control system for an array of qubits is disclosed. The control system according to the present invention provides currents and voltages to qubits in the array of qubits in order to perform functions on the qubit. The functions that the control system can perform include read out, initialization, and entanglement. The state of a qubit can be determined by grounding the qubit, applying a current across the qubit, measuring the resulting potential drop across the qubit, and interpreting the potential drop as a state of the qubit. A qubit can be initialized by grounding the qubit and applying a current across the qubit in a selected direction for a time sufficient that the quantum state of the qubit can relax into the selected state. In some embodiments, the qubit can be initialized by grounding the qubit and applying a current across the qubit in a selected direction and then ramping the current to zero in order that the state of the qubit relaxes into the selected state.

Abstract: Quantum computing systems and methods that use opposite magnetic moment states read the state of a qubit by applying current through the qubit and measuring a Hall effect voltage across the width of the current. For reading, the qubit is grounded to freeze the magnetic moment state, and the applied current is limited to pulses incapable of flipping the magnetic moment. Measurement of the Hall effect voltage can be achieved with an electrode system that is capacitively coupled to the qubit. An insulator or tunnel barrier isolates the electrode system from the qubit during quantum computing. The electrode system can include a pair of electrodes for each qubit. A readout control system uses a voltmeter or other measurement device that connects to the electrode system, a current source, and grounding circuits. For a multi-qubit system, selection logic can select which qubit or qubits are read.

Abstract: Quantum computing systems and methods that use opposite magnetic moment states read the state of a qubit by applying current through the qubit and measuring a Hall effect voltage across the width of the current. For reading, the qubit is grounded to freeze the magnetic moment state, and the applied current is limited to pulses incapable of flipping the magnetic moment. Measurement of the Hall effect voltage can be achieved with an electrode system that is capacitively coupled to the qubit. An insulator or tunnel barrier isolates the electrode system from the qubit during quantum computing. The electrode system can include a pair of electrodes for each qubit. A readout control system uses a voltmeter or other measurement device that connects to the electrode system, a current source, and grounding circuits. For a multi-qubit system, selection logic can select which qubit or qubits are read.

Abstract: A solid-state quantum computing structure includes a dot of superconductive material, where the superconductor possesses a dominant order parameter with a non-zero angular momentum and a sub-dominant order parameter that can have any pairing symmetry. Alternately a solid-state quantum computing structure includes an anti-dot, which is a region in a superconductor where the order parameter is suppressed. In either embodiment of the invention, circulating persistent currents are generated via time-reversal symmetry breaking effects in the boundaries between superconducting and insulating materials. These effects cause the ground state for the supercurrent circulating near the qubit to be doubly degenerate, with two supercurrent ground states having distinct magnetic moments. These quantum states of the supercurrents store quantum information, which creates the basis of qubits for quantum computing.

Abstract: A solid-state quantum computing structure includes a dot of superconductive material, where the superconductor possesses a dominant order parameter with a non-zero angular momentum and a sub-dominant order parameter that can have any pairing symmetry. Alternately a solid-state quantum computing structure includes an anti-dot, which is a region in a superconductor where the order parameter is suppressed. In either embodiment of the invention, circulating persistent currents are generated via time-reversal symmetry breaking effects in the boundaries between superconducting and insulating materials. These effects cause the ground state for the supercurrent circulating near the qubit to be doubly degenerate, with two supercurrent ground states having distinct magnetic moments. These quantum states of the supercurrents store quantum information, which creates the basis of qubits for quantum computing.