EPJ Quantum Technol. (2015) 2: 7
https://doi.org/10.1140/epjqt/s40507-015-0020-6

Research

Qubit decoherence due to detector switching

¹ Instituut Lorentz, Leiden University, Leiden, The Netherlands
² IQC and Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
³ Theoretical Physics, Saarland University, Saarbrücken, Germany

^* e-mail: fwm@lusi.uni-sb.de

Received: 23 October 2014
Accepted: 22 January 2015
Published online: 7 March 2015

Abstract

We discuss the noise occurring during a classical dissipative switching process as it would be detected by a quantum bit used as a detector for noise. In particular we study the switching-induced decoherence during escape events. We present a simple method to obtain analytical results for the qubit dephasing and bit-flip, which goes beyond the simple Born-Markov notion of the qubit as a spectrometer for noise but still allows us to correlate its behavior with the noise source. These results also provide insight into the qubit measurement process involving a switching type of detector, showing under which conditions switching detectors can be operated fast and with low error. In particular, the state in the end recovers from temporary bit flip errors due to an intrinsic approximate time reversal symmetry, whereas the switching process mostly produces low frequency pure dephasing noise.