2 seminars announced by CMSP Section

[Cond.Matt. & Stat.Mech.Section]

JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR



Tuesday, 11 December   -   11:30 hrs.

 

Luigi Stasi Seminar Room -   ICTP Leonardo Building - 1st floor

 

Gian Carlo GHIRARDI   ( University of Trieste )



"Entanglement, nonlocality, signaling and cloning"



Abstract


Quantum entanglement between two far-away constituents of a composite system, when considered in conjunction with a measurement process on one of them, raises some serious problems due to the instantaneous reduction of the state of the other. In some sense one could state that an action performed in a given space time region can affect immediately a system which is space like separated from it.

It is not surprising that this peculiar aspect of quantum mechanics has given rise, from the seventies up to now,  to many proposals to achieve superluminal communication between distant observers. Almost all such proposals have been shown to be wrong  on the basis of general theorems by P. Eberhard and by our group.

However, in 1982, a quite tricky new proposal has been put forward by N. Herbert whose refusal required the derivation of a new theorem, which has played and plays an important role for quantum computation and quantum communication: the no-cloning theorem.

The seminar intends to briefly review the debate about this interesting issue which involves many subtle aspects of quantum mechanics and to make clear the events which led to the derivation of the no-cloning theorem.

Finally, attention will be paid to the general problem of the compatibility of the reduction process "at-a-distance" and relativistic requirements, specifically in the light of the recent proposals of relativistic generalizations of  "collapse theories".



==


SEMINAR on   Disorder and strong electron correlations

 

Thursday, 13 December-  11:30 a.m.

 

Luigi Stasi Seminar Room,  Leonardo Building - first floor

 

Jonathan M.J. KEELING    ( University of St. Andrews )



"Condensation vs lasing and superfluidity of  coupled light-matter systems"

 

Abstract

 

The great experimental progress in realising and studying polariton condensates has made it possible to now study experimentally a number of fundamental questions about the relation between lasing, condensation, coherence and superfluidity.  In my talk, I will discuss the consequences of finite particle lifetime on several of these questions.  I will discuss the relation between lasing as described by the Maxwell-Bloch equations and polariton condensation, and discuss the consequences of this for both polariton and photon condensation [1].  I will also address aspects of superfluidity [2], pattern formation [3] and coherence[3], and discuss how these are  affected by the finite lifetime of polaritons.


[1] J. Keeling, M. H. Szymanska, and P. B. Littlewood p. 293 of Optical generation and control of quantum coherence in semiconductor

       nanostructures (2010) Eds. G. Slavcheva and P. Roussignol

[2] J. Keeling, Phys. Rev. Lett. 107 080402 (2011)

[3] J. Keeling and N. G. Berloff Phys. Rev. Lett. 100 250401 (2008)

[4] G. Roumpos et al, Proc. Natl. Acad. Sci, 109 6467(2012)