Quantum Noise in the Josephson Charge Qubit

Astafiev, Oleg V. and Pashkin, Yuri and Nakamura, Y. and Yamamoto, T. and Tsai, Jaw-Shen (2004) Quantum Noise in the Josephson Charge Qubit. Physical review letters, 93 (26). ISSN 0031-9007

Abstract

We study decoherence of the Josephson charge qubit by measuring energy relaxation and dephasing with help of the single-shot readout. We found that the dominant energy relaxation process is a spontaneous emission induced by quantum noise coupled to the charge degree of freedom. Spectral density of the noise at high frequencies is roughly proportional to the qubit excitation energy