QND Measurements in a Resonant Cavity-QED System

Jian Cheng Yang, Paul G. Kwiat

We theoretically study photon-photon interactions mediated by a cavity-atom system in the strong-coupling regime of cavity quantum electrodynamics (QED), which may be harnessed for quantum non-demolition (QND) measurements.

Andreas J. Wallraff, David Schuster, Alexandre Blais +10 more

In this paper, the coherent interaction of individual microwave photons with superconducting qubits is presented both for quantum information processing and for novel quantum optics experiments in the circuit quantum electrodynamics (QED) architecture. In the resonant regime we observe the vacuum Rabi mode splitting. In the non-resonant regime we use the dispersive coupling between the qubit and the cavity field to perform high visibility quantum non-demolition (QND) measurements of the qubit state. In the strong dispersive limit we also perform measurements of the cavity state from which the photon number statistics of the field can be extracted. Generally, the circuit QED architecture is attractive for quantum information processing and as an interface in hybrid quantum systems.

Pascal Degiovanni, Valentin Bonzom, Hichem Bouzidi +4 more

M. J. Woolley, Andrew C. Doherty, Gerard J Milburn

We propose a scheme for the quantum nondemolition (QND) measurement of Fock states of a nanomechanical resonator via feedback control of a coupled circuit QED system. A Cooper pair box (CPB) is coupled to both the nanoresonator and microwave cavity. The CPB is readout via homodyne detection on the cavity and feedback control is used to effect a nondissipative measurement of the CPB. This realizes an indirect QND measurement of the nanoresonator via a second-order coupling of the CPB to the nanoresonator number operator. The phonon number of the Fock state may be determined by integrating the stochastic master equation derived, or by processing of the measurement signal.

S. Haroche, I. Dotsenko, S. Gleyzes +2 more