Quantum behavior of a dc SQUID phase qubit

Kaushik Mitra; F. W. Strauch; C. J. Lobb; J. R. Anderson; F. C. Wellstood; Eite Tiesinga

doi:10.1103/PhysRevB.77.214512

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Quantum behavior of a dc SQUID phase qubit

Kaushik Mitra, F. W. Strauch, C. J. Lobb, J. R. Anderson, F. C. Wellstood, Eite Tiesinga

DOI 10.1103/PhysRevB.77.214512 · Physical Review B

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Abstract

We analyze the behavior of a dc superconducting quantum interference device 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 Schrödinger’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 nondestructive read out of the qubit state.