Upcoming seminars

The usual model for collisional thermal baths consists of a system interacting with small units drawn from a reservoir. The interaction must be switched on and off and this operation can involve the exchange of energy between the system and the external agent that connects and disconnects the interaction, and this energy has been considered work.

We present an efficient algorithm that solves the quantum state tomography problem from an arbitrary number of projective measurements in any finite dimension d. The algorithm is flexible enough to allow us to impose any desired rank r to the state to be reconstructed, ranging from pure (r=1) to full rank (r=d) quantum states. The method exhibits successful and fast convergence under the presence of realistic errors in both state preparation and measurement stages, and also when considering overcomplete sets of observables.

Quantum coherence, or the property of systems which are in a superposition of states yielding interference patterns in suitable experiments, is the main hallmark of departure of quantum mechanics from classical physics. Besides its fascinating epistemological implications, quantum coherence also turns out to be a valuable resource for quantum information tasks, and has even been used in the description of fundamental biological processes.

The quantum Stein's Lemma gives the asymptotic error for simple i.i.d. hypothesis testing between two states, where the type-I  error is bounded away from 1, and the type-II error is exponentially small. The exponent is given by the quantum relative entropy between the states. The corresponding question for quantum channels (cptp maps) a priori has two answers, depending on whether we allow adaptive strategies to discriminate the channels or not. In a series of recent papers, Berta et al. (1808.01498), Wang/Wilde (1907.06306) and Fang et al.