"Just over one hundred and fifty years ago, Maxwell first posed the thought experiment that became known as “Maxwell’s demon.” Designed to understand more deeply the nature of the newly formulated second law of thermodynamics, the demon was to play a long, controversial role in the development of statistical physics. Just two months later, Maxwell’s paper “On governors” gave the first analysis of a feedback system. These two foundational works reflect the fundamental and practical aspects of control. I will present an experiment that unites the two: using feedback to create “impossible” dynamics, we make a Maxwell demon that can reach the fundamental limits to control set by thermodynamics. We test—and then extend—Rolf Landauer’s 1961 prediction that information erasure requires at least as much work as can be extracted from a system by virtue of information. We use this identity to infer the form of the two-state nonequilibrium entropy function (Gibbs-Shannon entropy). These fundamental thermodynamic tests are benchmarks for evaluating the performance of practical information engines, such as those active within cells and other complex systems."

"This talk will deal with the problem of two qubit entanglement. As is well known, the Poincare-Bloch sphere gives an elegant visualisation of the pure states of a qubit and its interior describes the impure states. After an elementary introduction, this talk will give a characterisation of the impure states of the two qubit system. The approach is based on Lorentzian geometry and gives a new way to detect qubit entanglement. The treatment is based physically, on the causal structure of Minkowski spacetime, and mathematically, on a Lorentzian Singular Value Decomposition. A surprising feature is the natural emergence of ‘‘Energy conditions’’ used in Relativity. All states satisfy a ‘‘Dominant Energy Condition’’ (DEC) and separable states satisfy the Strong Energy Condition(SEC), while entangled states violate the SEC. We thus propose a test for two qubit entanglement which is an alternative to the positive partial transpose (PPT) test. This test is based on the partial Lorentz transformation (PLT) on individual qubits. Apart from testing for entanglement, our approach also enables us to construct a separable form for the density matrix in those cases where it exists. Our approach leads to a simple graphical three dimensional representation of the state space which shows the entangled states within the set of all states. This talk will deal with the problem of two qubit entanglement. As is well known, the Poincare-Bloch sphere gives an elegant visualisation of the pure states of a qubit and its interior describes the impure states. After an elementary introduction, this talk will give a characterisation of the impure states of the two qubit system. The approach is based on Lorentzian geometry and gives a new way to detect qubit entanglement. The treatment is based physically, on the causal structure of Minkowski spacetime, and mathematically, on a Lorentzian Singular Value Decomposition. A surprising feature is the natural emergence of ‘‘Energy conditions’’ used in Relativity. All states satisfy a ‘‘Dominant Energy Condition’’ (DEC) and separable states satisfy the Strong Energy Condition(SEC), while entangled states violate the SEC. We thus propose a test for two qubit entanglement which is an alternative to the positive partial transpose (PPT) test. This test is based on the partial Lorentz transformation (PLT) on individual qubits. Apart from testing for entanglement, our approach also enables us to construct a separable form for the density matrix in those cases where it exists. Our approach leads to a simple graphical three dimensional representation of the state space which shows the entangled states within the set of all states."

"We analyse diffusion at low temperature by bringing the fluctuation-dissipation theorem (FDT) to bear on a physically natural, viscous response-function R(t). The resulting diffusion-law exhibits several distinct regimes of time and temperature, each with its own characteristic rate of spreading. As with earlier analyses, we find logarithmic spreading in the quantum regime, indicating that this behaviour is robust. A consistent R(t) must satisfy the key physical requirements of Wightman positivity and passivity, and we prove that ours does so. We also prove in general that these two conditions are equivalent when the FDT holds. Given current technology, our diffusion law can be tested in a laboratory with ultra cold atoms."

"TEW"