Quantum state reconstruction in the presence of dissipation

Abstract

Abstrac t.We propose a realistic scheme to determine the quantum state of a single-mode cavity ® eld even after it has started to decay due to the coupling with an environment. Although dissipation destroys quantum coherences, we show that at zero temperature enough information about the initial state remains, in an observable quantity, to allow the reconstruction of its Wigner function.

Entropy Operator and Associated Wigner Function

“…The conection with quasiprobability distribution functions [10,11], in particular the association to the Wigner function for the entropy has been obtained.…”

NOON states in entangled cavities

“…extended the regime to microwave cavities. Measurement of cavity fields may be done via quantum state reconstruction even in the presence of dissipation [20].…”

Direct measurement of the Q-function in a lossy cavity

“…During the past years, several techniques have been developed, for instance the direct sampling of the density matrix of a signal mode in multiport optical homodyne tomography [3], tomographic reconstruction by unbalanced homodyning [4], reconstruction via photocounting [5], cascaded homodyning [6] to cite some. There have also been proposals to measure electromagnetic fields inside cavities [7,8] and vibrational states in ion traps [7,9]. In fact the full reconstruction of nonclassical states of the electromagnetic field [10] and of (motional) states of an ion [11] have been experimentally accomplished.…”

“…Schemes that treat a lossy cavity have been proposed [8] that involve a physical process that allows the storage of information about the quantum coherences of the initial state in the diagonal elements of the density matrix of a transformed state. Here, we would like to re-take the problem of reconstruction of the cavity field as studied in [7], but allowing the cavity to have losses (i.e.…”