Quantum behavior of the dc SQUID phase qubit

Abstract

We analyze the behavior of a dc Superconducting Quantum Interference Device (SQUID) phase qubit in which one junction acts as a phase qubit and the rest of the device provides isolation from dissipation and noise in the bias leads. Ignoring dissipation, we find the two-dimensional Hamiltonian of the system and use numerical methods and a cubic approximation to solve Schrodinger's equation for the eigenstates, energy levels, tunneling rates, and expectation value of the currents in the junctions. Using these results, we investigate how well this design provides isolation while preserving the characteristics of a phase qubit. In addition, we show that the expectation value of current flowing through the isolation junction depends on the state of the qubit and can be used for non-destructive read out of the qubit state.

38 pages, 7 figures

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• Self-excited current oscillations in a resonant tunneling diode described by a model based on the Caldeira-Leggett Hamiltonian
• Intermode Dephasing in a Superconducting Stripline Resonator - Supplementary Information
• A new approach to the quantization of the damped harmonic oscillator
• Efficient numerical simulation of complex Josephson quantum circuits
• Two-dimensional tunneling in a SQUID