Regular Article

Quantum-enhanced interferometry with cavity QED-generated non-classical light

¹ Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
² Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21, 6020 Innsbruck, Austria

^a e-mail: jan.chwedenczuk@fuw.edu.pl

Received: 4 April 2017
Received in final form: 25 July 2017
Published online: 2 November 2017

Abstract

We propose an enhanced optical interferometer based on tailored non-classical light generated by nonlinear dynamics and projective measurements in a three-level atom cavity QED system. A coherent state in the cavity becomes dynamically entangled with two ground states of the atom and is transformed to a macroscopic superposition state via a projective measurement on the atom. We show that the resulting highly non-classical state can improve interferometric precision measurements well beyond the shot-noise limit once combined with a classical laser pulse at the input of a Mach–Zehnder interferometer. For a practical implementation, we identify an efficient phase shift estimation scheme based on the counting of photons at the interferometer output. Photon losses and photon-counting errors deteriorate the interferometer sensitivity, but we demonstrate that it still can be significantly better than the shot-noise limit under realistic conditions.