State measurements of flux-based superconducting quantum bits (qubits) require the sensitive discrimination of small differences of magnetic flux, with measurement times short compared to the timescales of coherent quantum mechanical behaviour. The single-fluxquantum (SFQ) superconducting comparator may be the best device for this purpose. An SFQ comparator design using a quasi-one-junction SQU...

A controllable p-SQUID is a DC SQUID ~direct-current superconducting quantum interference device! with two controllable p junctions as weak links. A controllable p junction consists of a superconducting–normal metal–superconducting Josephson junction with two additional contacts to the normal region of the junction. By applying a voltage Vc over these contacts it is possible to control the stat...

Recent successes with superconducting Josephson junction qubits make them prime candidates for the implementation of quantum computing. This doctoral thesis details the study of a niobium Josephson junction circuit for quantum computing applications. The thesis covers two main areas: 1) the fabrication of sub-micron niobium Josephson junction devices using a Nb/Al/AlO./Nb trilayer process and 2...

The device operates at temperatures <300 mK and comprises a hafnium microbridge superconducting aluminum tunnel junction both integrated into common coplanar waveguide. matches with planar antenna as an optical blackbody frequencies 600-700 GHz. terminal is the output in 1-2 GHz frequency range. temperature can be set range of 0.4-9 K calibrated using shot noise junction. Temperature mod...

Solid-state qubits have the potential for the large-scale integration and for the flexibility of layout for quantum computing. However, their short decoherence time due to the coupling to the environment remains an important problem to be overcome. We propose a new superconducting qubit which incorporates a spin-electronic device: the qubit consists of a superconducting ring with a ferromagneti...

We present the first experimental results on a device with more than two superconducting qubits. The circuit consists of four three-junction flux qubits, with simultaneous ferro- and antiferromagnetic coupling implemented using shared Josephson junctions. Its response, which is dominated by the ground state, is characterized using low-frequency impedance measurement with a superconducting tank ...

We report the design and measurement of superconducting/normal/superconducting SNS proximity dc squids in the long-junction limit, i.e., superconducting loops interrupted by two normal metal wires, which are roughly a micrometer long. Thanks to the clean interface between the metals, a large supercurrent flows through the device at low temperature. The dc squidlike geometry leads to an almost c...

A theory describing the operation of a superconducting nanowire quantum interference device NQUID is presented. The device consists of a pair of thin-film superconducting leads connected by a pair of topologically parallel ultranarrow superconducting wires. It exhibits intrinsic electrical resistance, due to thermally activated dissipative fluctuations of the superconducting order parameter. At...

We show that the quantum properties of some Josephson SQUID devices are described by a boundary sine Gordon model. Our approach naturally describes multi-junction SQUID devices and, when applied to a single junction SQUID (the rf-SQUID), it reproduces the known results of Glazman and Hekking. We provide a detailed analysis of the regimes accessible to an rf-SQUID and to a two-Josephson junction...