Creating and sharing knowledge for telecommunications

Seminar - Universal single-frequency oscillation of the entanglement spectrum after a local quench

on 25-03-2015

... Abolfazl Bayat, University College London

25/03/2015, 10:00
Room P3.10, Mathematics Building, IST

Long-lived single-frequency oscillations in the local non-equilibrium dynamics of a quantum many-body system is an exceptional phenomenon. In fact, till now, it has never been observed, nor predicted, for the physically relevant case where a system is prepared to be quenched from one quantum phase to another. Here we show how the quench dynamics of the entanglement spectrum may reveal the emergence of such oscillations in a correlated quantum system with Kondo impurities. The oscillations we find are characterized by a single frequency which is proportional to the Kondo temperature of the system. The frequency is universal, being independent of the amount of energy released by the local quench, and scales as 1/N for N being the size of the system. Importantly, the universal frequency manifests itself also in local observables, such as the spin-spin correlation function of the impurities.

Quantum Computation and Information Seminar

Support: Phys-Info (IT), SQIG (IT), CFIF and CAMGSD, with support from FCT, FEDER and EU FP7, namely via the Doctoral Programme in the Physics and Mathematics of Information (DP-PMI), and projects PEst-OE/EEI/LA0008/2013, QuSim, CQVibes, Landauer (318287) and PAPETS (323901). More Information..

Seminar - Generalized Landauer Bound as Universal Thermodynamic Entropy in Continuous Phase Transitions

on 24-03-2015

... Cristina Diamantini (University of Perugia)
Date & time: 24/03/2015 at 10:00.
Location: Seminar Room (2.8.3), Physics Department, Instituto Superior Técnico, Lisbon.

The classic Landauer bound can be lowered when erasure errors are permitted. Here we point out that continuous phase transitions characterized by an order parameter can also be viewed as information erasure by resetting a certain number of bits to a standard value. The information-theoretic expression for the generalized Landauer bound in terms of error probability implies thus a universal form for the thermodynamic entropy in the partially ordered phase. We explicitly show that the thermodynamic entropy as a function of interaction parameters and temperature is identical to the information-theoretic expression in terms of error probability alone in the specific example of the Hopfield neural network model of associative memory, a distributed information-processing system of many interacting stochastic bits. In this framework the Landauer bound sets a lower limit for the work associated with "remembering" rather than "forgetting".

Physics of Information Seminar

Supported with funding from FCT, FEDER and EU FP7, namely via projects PEst-OE/EEI/LA0008/2013, UID/EEA/50008/2013, IT/QuSim, CQVibes, Landauer (318287) and PAPETS (323901). More Information..