Quantum Computation with Superconducting Circuits

Quantum computation, when fully realized, will offer tremendous benefits to all of science. To develop a quantum computer we must meet DiVincenzo’s criteria - we must have: An extensible array of qubits which can be distinguished from one another; a mechanism for initializing the qubits to a reference state; the ability to measure the state of any single qubit; a universal set of operations; and we must have a coherence time long enough to apply error correction techniques. The Josephson phase qubit, which uses the phase across a Josephson junction as its quantum variable, promises to meet these requirements. Because it is a macroscopic device it is easily distinguishable, and individual qubits can be measured independently. It is scalable via capacitive or inductive coupling, Josephson junctions can be used to provide negative inductance for controlled coupling. Initialization is provided by resistive damping of the oscillations, which resets the qubit to the |0> state. The qubits can achieve computational universality by the controlled-not gate, though we still have to increase their coherence time by roughly five orders of magnitude for error correction. This project entails the development of quantum simulations for characterization of these qubits and analysis of experiments.