Charge echo in a cooper-pair box.
A spin-echo-type technique is applied to an artificial two-level system that utilizes a charge degree of freedom in a small superconducting electrode. Gate-voltage pulses are used to produce the necessary pulse sequence in order to eliminate the inhomogeneity effect in the time-ensemble measurement and to obtain refocused echo signals. Comparison of the decay time of the observed echo signal with an estimated decoherence time suggests that low-frequency energy-level fluctuations due to the 1/f charge noise dominate the dephasing in the system.
Nakamura
Y
Y
NEC Fundamental Research Laboratories, Tsukuba, Ibaraki 305-8501, Japan.
Pashkin
Yu A
YA
Yamamoto
T
T
Tsai
J S
JS