Maximally entangled states, pair-superfluidity and MORE in a many-body interacting system
le jeudi 29 juin 2017 à 13h30

Séminaire LPMMC

Personne à contacter : Dominique Spehner ()

Lieu : Salle de lecture 2, maison des Magistères

Résumé : In this talk I will present interesting results about the study of quantum correlations
between two species of ultra-cold bosons living on a ring lattice. In the first part, I
going to show that the presence of synthetic magnetic fields can lead to the formation
of entangled states between pair of qudits (high dimensional qubits). Notably,
maximally entangled eigenstates are possible to find for well-defined values of the
Aharonov-Bohm phase of the synthetic magnetic field, which are zero-energy
eigenstates of both the kinetic and interacting parts of the Bose-Hubbard Hamiltonian
[1]. This latter property makes them exeptional and robust for applications. In the
second part, I will focus on the eigenstates of the lowest-energy band in the regime
of large interaction where a pair-superfluid phase naturally emerge for the ground
state. In this scenario, the analysis of the interference pattern in the momentum
distribution indicates a strong connection between entanglement and the pair-
superfluid phase. This is further highlighted by the fact that for maximally entangled
eigenstates any single order tunneling process is naturally suppressed [2]. Thus the
observation of features of a pair-superfluid behavior can be used as a signature of
the presence of entanglement. This might be an important tool for the
characterization of the entanglement in the ground state. Finally, I will discuss the
perspective of using this setting with two type of particles as a benchmark to
investigate the connection between phase coherence and entanglement in many-
body quantum systems.

References

[1]
S. A. Reyes, L. Morales-Molina, M. Orszag, and D. Spehner, EPL 108, 20010
(2014).

[2] L. Morales-Molina, S. A. Reyes and E. Arevalo, EPL 115, 36004 (2016).

The arrow of time for continuous quantum measurements
le vendredi 30 juin 2017 à 11h00

Séminaire théorie

Personne à contacter :

Lieu : Amphithéâtre, maison des Magistères

Résumé : The question of the time reversibility of quantum mechanics with
measurements is one that has been debated for some time. In this
talk, I will present new work exploring our ability to distinguish the
forward from the time-reverse measurement records of continuous
quantum measurements. The question involves both the conditions for
the time-reversibility of the quantum trajectory equations of motion,
as well as statistical distinguishability of the arrow of time. For a
continuous qubit measurement example, we demonstrate that
time-reversed evolution is physically possible, provided that the
measurement record is also negated. Despite this restoration of
dynamical reversibility, a statistical arrow of time emerges, and may
be quantified by the log-likelihood difference between forward and
backward propagation hypotheses. We then show that such reversibility
is a universal feature of non-projective measurements, with forward or
backward Janus measurement sequences that are time-reversed inverses
of each other.
J. Dressel, A. Chantasri, A. N. Jordan, A. N. Korotkov, arXiv:1610.03818