THE LOSS OF FIDELITY DUE TO QUANTUM LEAKAGE FOR JOSEPHSON CHARGE QUBITS.

In this paper we calculate the loss of fidelity due to quantum leakage for the Josephson charge qubit (JCQ). In this investigation the characteristic values and characteristic states of the Mathieu equation are used. It is shown that for present typical parameters of JCQ, EJ/Ech ~ 0.02, the loss of the fidelity per elementary operation is about 10-4 which satisfies DiVincenzo's low decoherence criterion. By appropriately improving the designs of the Josephson junction, namely, decreasing EJ/Ech to ~ 0.01, the loss of fidelity per elementary operation can decrease even smaller to 10-5. The first-order nonadiabatic correction is also obtained by using the approach. [ABSTRACT FROM AUTHOR]