Institute of Quantum Physics

Does Zeno freeze the evolution? On quantum heating, cooling and freezing

Prof. Dr. Gershon Kurizki, Weizmann Institute of Science, Rehovot, Israel
Th, 18.6.2009, 13:30 Uhr
O26/4309

Enlightened atoms rebel against uniformity

Prof. Alexander Kaplan, Johns Hopkins University, Baltimore
Mo, 6.7.2009, 11:00 Uhr
O26/4309

Quantum process and state tomography: new efficient algorithms

Prof. Juan Pablo Paz, Universidad de Buenos Aires, Argentinien
Fr, 10.7.2009, 15:00 Uhr
N24/252

Linear amplification and quantum cloning for non-Gaussian continuous variables

Prof. Hyunchul Nha, Texas A & M University at Qatar
Mo, 13.7.2009, 14:00 Uhr
N24/226

We investigate the phase-insensitive linear amplification at quantum limit for single-mode and two-mode states and obtain the critical gains at which nonclassical properties disappear in the output. We show that there exist nonclassical effects persisting even at an extremely large gain including, remarkably, two-mode entanglement. We identify these effects in experimentally observable forms and also discuss the implications of our results in a quantum-cloning context.

Radiation of one quantum by many atoms

Prof. Roy Glauber, Harvard University
Tu, 14.7.2009, 11:00 Uhr
N24/227

The visualization of quantum field theory

Prof. Rainer Grobe, llinois State University
Th, 16.7.2009, 14.00 Uhr
H7

Open Quantum Systems: Cavity QED with Dissipation

Prof. Howard Carmichael, The University of Auckland
Mo, 20.7.2009, 11:00 Uhr
H6

The Jaynes-Cummings model with dissipation has for many years been a fundamental model of optical frequency cavity QED. Little attention has been payed, however, to the unique consequences of the added dissipation: the possible occurrence of dissipative quantum phase transitions when the system is driven far away from thermal equilibrium. Over nearly two decades, experiments in cavity QED have focused on physics seen at the weakest levels of excitation---such things as vacuum Rabi splitting, single-photon sources, and two-photon correlations. While the last of these begins to probe the unique nonlinearity of the Jaynes-Cummings spectrum, the features attracting experimental attention are realized with sources that emit far less than one photon per cavity lifetime. My talk will review this background, and then move on to the new physics that arises when highly excited states of the dissipative Jaynes-Cummings model are accessed. The second part of the talk takes its inspiration from recent advances in circuit QED, where states of a few intracavity quanta are observed. It concludes with recent theoretical results which demonstrate the existence of a dissipative quantum phase transition under conditions of very strong coupling and high excitation.

Exact Disentanglement Calculations

Prof. Dr. Bob O’Connell, Lousiana State University, Baton Rouge
We, 22.7.2009, 11:00 Uhr
N24/252

We consider a simple correlated two-body continuous variable system which enables us (a) in the absence of a heat bath, to judge results obtained from various entanglement measures [1], (b) to show that disentanglement can occur at non-zero temperatures in the absence of dissipation [2], (c) in the presence of an Ohmic heat bath, calculate exactly the dependence of sudden death of entanglement (SDI) on dissipation and temperature [2], and (d) for the case of a coupled free particle superposition state in an arbitrary heat bath, to present persuasive evidence that both decoherence and disentanglement decay exponentially, indicating that SDI is absent [2].
[1] G. W. Ford, Y. Gao and R. F. O'Connell, to be published.
[2] G. W. Ford and R. F. O'Connell, to be published.