Undoing measurement-induced dephasing in circuit QED

A. Frisk Kockum*, L. Tornberg, G. Johansson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We analyze the backaction of homodyne detection and photodetection on superconducting qubits in circuit quantum electrodynamics. Although both measurement schemes give rise to backaction in the form of stochastic phase rotations, which leads to dephasing, we show that this can be perfectly undone provided that the measurement signal is fully accounted for. This result improves on an earlier one, showing that the method suggested can be made to realize a perfect two-qubit parity measurement. We propose a benchmarking experiment on a single qubit to demonstrate the method using homodyne detection. By analyzing the limited measurement efficiency of the detector and bandwidth of the amplifier, we show that the parameter values necessary to see the effect are within the limits of existing technology.

Original languageEnglish
Article number052318
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number5
StatePublished - 24 May 2012
Externally publishedYes


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