Maximized information on the environment by dynamically controlled qubit probes

ANALIA ZWICK

Seminario; Seminar in Harvard University invited by Dr. Micha Lukin; 2015

Harvard

Talk: Controlled quantum spins are sensitive probes of the environment and a powerful tool for characterizing highly complex quantum systems at a molecular or atomic scale. Novel quantum technologies requiring high sensitivity at the nanoscale are based on quantum spin probes serving as magnetometers, thermometers, sensors for imaging or monitoring biological process. We explore the ability of a qubit probe to characterize unknown parameters of its environment. By resorting to quantum estimation theory, we analytically find the ultimate bound on the precision of estimating key parameters of a broad class of ubiquitous environmental noises("baths") which the qubit may probe. These include the probe-environment coupling strength and the environmental correlation time of the non-Markovian generalized Ornstein-Uhlenbeck and Ohmic processes. We demonstrate that by optimizing the dynamical control on the probe under realistic constraints one may attain the maximal accuracy bound within the least number of measurements.Applications of this protocol that combines dynamical control and estimation theory tools to quantum sensing of physical, chemical and biological process are envisaged and illustrated for a nitrogen-vacancy (NV) center in diamond used as a probe.