Noisy coherent population trapping: applications to noise estimation and qubit state preparation

Arshag Danageozian, Ashe Miller, Pratik J Barge, Narayan Bhusal, Jonathan Dowling

Abstract:

Coherent population trapping is a well-known quantum phenomenon in a driven Λ system,
with many applications across quantum optics. However, when a stochastic bath is present in
addition to vacuum noise, the observed trapping is no longer perfect. Here we derive a
time-convolutionless master equation describing the equilibration of the Λ system in the
presence of additional temporally correlated classical noise, with an unknown decay
parameter. Our simulations show a one-to-one correspondence between the decay parameter
and the depth of the characteristic dip in the photoluminescence spectrum, thereby enabling
the unknown parameter to be estimated from the observed spectra. We apply our analysis to
the problem of qubit state initialization in a Λ system via dark states and show how the
stochastic bath affects the fidelity of such initialization as a function of the desired dark-state
amplitudes. We show that an optimum choice of Rabi frequencies is possible.