ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT wigner.mta.hu>]

*Wigner FK Quantum Optics and Quantum Information Seminar*
Generalized Zeno dynamics, adiabatic theorems  and  ergodic means

*Norbert Barankai*
MTA-ELTE Theoretical Physics Research Group

Tuesday, 22 January 13:30, KFKI Campus, Bldg. 1, 1st floor, Conference Room

In recent years, there has been a growing interest in the application of
the Zeno effect to quantum state protection. The Zeno effect has a long
history and it is frequently associated with some kind of a strong
measurement operation performed on a quantum state which tries to localize
the system in a preferred subspace.

However, projective measurements  are not the only possible ways with which
control can be achieved. In this lecture, I will summarize some recent
results which generalize the Zeno effect to frequent disturbance of the
system by contractive quantum operations, for instance unitary kicks or
weak measurements. The calculations are not restricted to Hamiltonian
dynamics and does not assume the in-time translation invariance of the
generator of the time evolution operator. We show that, whenever an ergodic
mean of the generator exists, than the frequently disturbed time evolution
converges to a dynamics determined by that generator. The technical results
which provide estimates on the error terms of the limit procedure are also
capable to prove some kind of adiabatic theorems. Thus, a mathematical
framework to unify the three faces of the Zeno phenomenon (frequent
measurements, frequent unitary kicks, adiabatic limits) having been
recognized some fifteen years ago by Paolo Facchi, emerges.

Joint work with Zoltán Zimborás.  arXiv:1811.02509

Everyone is welcome to attend.

János Asbóth