Measuring the individual elements of the optical density matrix
Kenneth L. Pregnell, David Thomas Pegg · Griffith Research Online · 2003
Most methods for experimentally reconstructing the quantum state of light involve determining a quasiprobability distribution such as the Wigner function. In this paper we present a scheme for measuring individual density matrix elements in the photon number state representation. Remarkably, the scheme is simple, involving two beam splitters and a reference field in a coherent state.