Process tomography of field damping and measurement of Fock state lifetimes by quantum non-demolition photon counting in a cavity
Abstract
The relaxation of a quantum field stored in a high-Q superconducting cavity is monitored by non-resonant Rydberg atoms. The field, subjected to repetitive quantum non-demolition (QND) photon counting, undergoes jumps between photon number states. We select ensembles of field realizations evolving from a given Fock state and reconstruct the subsequent evolution of their photon number distributions. We realize in this way a tomography of the photon number relaxation process yielding all the jump rates between Fock states. The damping rates of the n photon states (0≤ n ≤ 7) are found to increase linearly with n. The results are in excellent agreement with theory including a small thermal contribution.
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