Coherent control and charge echo in a GaAs charge qubit

Abstract

In fulfilling the non-adiabatic requirement of pulse sequences, it is challenging to perform multi-pulse quantum control of a charge qubit. By optimizing our charge qubit and pulse parameters, we experimentally demonstrate the coherent control and echo process of a GaAs charge qubit. We firstly employed a single non-adiabatic voltage pulse to perform the Larmor oscillation experiment and determine the optimal operation pulses. Then, we produced Ramsey fringes using two pulses and extracted the decoherence time from the Ramsey fringes. More importantly, we successfully applied a charge echo pulse sequence to increase the extracted inhomogeneous dephasing time to ∼1360 ps. Our results show that the low-frequency noise is the important dephasing limiter of the coherence time of the charge qubit in the GaAs system.