Transport, atom blockade and output coupling in a Tonks-Girardeau gas

Recent experiments have demonstrated how quantum-mechanical impurities can be created within strongly correlated quantum gases and used to probe the coherence properties of these systems [S. Palzer, C. Zipkes, C. Sias, and M. K\"ohl, Phys. Rev. Lett. 103, 150601 (2009).]. Here we present a phenomenological model to simulate such an output coupler for a Tonks-Girardeau gas that shows qualitative agreement with the experimental results for atom transport and output coupling. Our model allows us to explore nonequilibrium transport phenomena in ultracold quantum gases and leads us to predict a regime of atom blockade, where the impurity component becomes localized in the parent cloud despite the presence of gravity. We show that this provides a stable mixed-species quantum gas in the strongly correlated limit

An eccentrically perturbed Tonks-Girardeau gas

We investigate the static and dynamic properties of a Tonks-Girardeau gas in a harmonic trap with an eccentric $\delta$-perturbation of variable strength. For this we first find the analytic eigensolution of the single particle problem and use this solution to calculate the spatial density and energy profiles of the many particle gas as a function of the strength and position of the perturbation. We find that the crystal nature of the Tonks state is reflected in both the lowest occupation number and momentum distribution of the gas. As a novel application of our model, we study the time evolution of the the spatial density after a sudden removal of the perturbation. The dynamics exhibits collapses and revivals of the original density distribution which occur in units of the trap frequency. This is reminiscent of the Talbot effect from classical optics.Comment: Comments and suggestions are welcom

The pinning quantum phase transition in a Tonks Girardeau gas: diagnostics by ground state fidelity and the Loschmidt echo

We study the pinning quantum phase transition in a Tonks-Girardeau gas, both in equilibrium and out-of-equilibrium, using the ground state fidelity and the Loschmidt echo as diagnostic tools. The ground state fidelity (GSF) will have a dramatic decrease when the atomic density approaches the commensurate density of one particle per lattice well. This decrease is a signature of the pinning transition from the Tonks to the Mott insulating phase. We study the applicability of the fidelity for diagnosing the pinning transition in experimentally realistic scenarios. Our results are in excellent agreement with recent experimental work. In addition, we explore the out of equilibrium dynamics of the gas following a sudden quench with a lattice potential. We find all properties of the ground state fidelity are reflected in the Loschmidt echo dynamics i.e., in the non equilibrium dynamics of the Tonks-Girardeau gas initiated by a sudden quench of the lattice potential

Boson Pairs in a One-dimensional Split Trap

We describe the properties of a pair of ultracold bosonic atoms in a one-dimensional harmonic trapping potential with a tunable zero-ranged barrier at the trap centre. The full characterisation of the ground state is done by calculating the reduced single-particle density, the momentum distribution and the two-particle entanglement. We derive several analytical expressions in the limit of infinite repulsion (Tonks-Girardeau limit) and extend the treatment to finite interparticle interactions by numerical solution. As pair interactions in double wells form a fundamental building block for many-body systems in periodic potentials, our results have implications for a wide range of problems.Comment: 9 pages, 8 figure

How Much Surveillance is Too Much? Some Thoughts on Surveillance, Democracy, and the Political Value of Privacy

Over the past decade it has become increasingly common to speak of the emergence of a surveillance society. Surveillance is an almost inescapable part of 21st century life. There is a very real danger that individual privacy - as it is currently understood - may soon become a thing of the past. Some would argue privacy is already dead and we have no choice but to accept our newly transparent lives. For many, surveillance has become part of daily life during visit banks, stores, shopping malls, and many public streets and parks. Travel through airports subjects our bodies to physical scans and our passports to electronic scrutiny. Attendees of public gatherings and demonstrations are often overtly captured on police CCTV video cameras. Perhaps the most profound expansion of surveillance has been in the area of dataveillance. Both the state and the private sector routinely require individuals to hand over large amounts of personal information as a matter of law or in exchange for access to services. The private sector owns vast amounts of information about us and processes and shares that information to create consumer profiles capable of accurately predicting individual consumption preferences. The intrusion of surveillance and dataveillance into every aspect of our lives hampers the degree to which individuals are able to construct and control different context-specific social identities. Our ability to function in society rests partly on our ability to keep these social roles separate. surveillance posses a very real threat to teh possibility of living complex, multi-layered social lives. This chapter considers question of how surveillance might affect the proper functioning of the rule of law, and the related question of how much surveillance is too much in a democratic society. The author considers: (1) the role of privacy in the protection of political rights; and (2) how much surveillance is too much

Surveillance and the Political Value of Privacy

The steady expansion in the use of surveillance technologies by the state and private sector represents a substantial threat to the privacy of ordinary individuals. Yet despite the best efforts of civil libertarians, many members of the public still struggle to understand why privacy is valuable and deserves to be protected as a basic right. In part, this is a result of the inherent complexity of the idea of privacy, but it is also due a tendency on the part of privacy advocates to focus on the individual - as opposed to the social and political dimensions - of privacy. In order to ensure that there is a greater level of public engagement with matters of privacy and sufficient awareness of the dangers of intrusive surveillance, more must be done to ensure that the general public appreciates that privacy is not just essential for individual freedom, but also for the health of society as a whole

CCTV and Human Rights

This chapter provides a brief overview of the human rights implications of closed circuit television (CCTV) surveillance, and aims to help CCTV managers and operators develop public area surveillance policies and practices that are consistent with a commitment to the protection of individual rights and a respect for civil liberties