Simulations and experimental observation of critical effects in the estimation precision of an environmental parameter using a quantum sensor under dynamical control

M. C. RODRIGUEZ; ANALIA ZWICK; GONZALO A. ALVAREZ

Congreso; XXI Giambiagi Winter School Quantum simulations and quantum metrology with cold trapped ions.; 2019

A quantum-probe is a useful diagnostic tool to obtain information about its environment. The quantum-sensor experiments decoherence, which depends on thespectral decomposition of the noise. Applying control sequences on a qubit-probe, filter functions are generated to selectively probe the spectral density thatcharacterizes the environment. For known shapes of the spectral density, we exploit the quantum sensor to estimate an environment parameter: the noisecorrelation time or spectral density width. Under dynamic control, the attained precision in the estimation of an environmental parameter exhibits a criticalbehavior as a function of a control parameter. We study this critical behavior using simulations and experiments. We observe the transition between twodynamical regimes distinguished by the critical behavior of the environmental information given by the estimated parameter. A sharp transition characterizes ashort and long environmental memory time compared with the probing-time. In addition we study different approaches to obtain this environmental parameter.