Fast, High-Fidelity, Quantum Non-demolition Readout of a Superconducting Qubit Using a Transverse Coupling

Author(s)

Raymond W. Simmonds, Jose A. Aumentado, Kurt Jacobs, Bryan Gard

Abstract

While relatively easy to engineer, transverse coupling between a qubit and a cavity mode satisfies the criteria for a quantum non-demolition (QND) measurement only if the coupling between the qubit and cavity is much less than their mutual detuning. This requirement in turn places a significant limit on the speed of the measurement. Here, we study the full transverse interaction between a qubit and a cavity mode, without the rotating-wave or dispersive approximations, in a circuit in which the interaction can be turned on and off. We show that by carefully choosing the interaction time and the detuning, and squeezing the cavity mode, it is possible to make very fast, high fidelity, highly QND measurements by exploiting a recurrence in the dynamics. We also show that the non-demolition property of the off-resonant approximation breaks down much faster than its dispersive property, implying that most dispersive measurements to-date have been implemented outside the QND regime.

Citation

Physical Review Letters

Pub Type

Journals

Keywords

dispersive measurement, superconducting qubits, quantum information

Citation

Simmonds, R. , Aumentado, J. , Jacobs, K. and Gard, B. (1970), Fast, High-Fidelity, Quantum Non-demolition Readout of a Superconducting Qubit Using a Transverse Coupling, Physical Review Letters (Accessed October 17, 2025)