Quantum state steering using weak measurements
ABSTRACT :
The state of a quantum system may be steered towards a predesignated target state, employing a sequence of weak blind measurements (where the detector’s readouts are traced out). In this seminar, I will present the steering of a single-qubit and two-qubit system using the interplay of a system Hamiltonian and weak measurements and sh ow that any pure or mixed state can be targeted. I will show that the optimization of such a steering protocol is underlain by the presence of Liouvillian exceptional points. More specifically, for high-purity target states, optimal steering implies purely relaxational dynamics marked by a second-order exceptional point, whereas for low-purity target states, it implies an oscillatory approach to the target state. The dynamical phase transition between these two regimes is characterized by a third-order exceptional point. In the two-qubit state steering protocol, I will discuss that through a continuous variation of the protocol parameters, one can guide a classical target state to a discorded one, and further on, toward an entangled target state.