Talks

Thermodynamics places surprisingly few fundamental constraints on information processing. In fact, most people would argue that it imposes only one, known as Landauer's Principle: a process erasing one bit of information must release an amount kT ln 2 of heat. It is this simple observation that finally led to the exorcism of Maxwell's Demon from statistical mechanics, more than a century after he first appeared. Ignoring the lesson implicit in this early advance, however, quantum information theorists have been surprisingly slow to embrace erasure as a fundamental primitive. Over the past couple of years, however, it has become clear that a detailed understanding of how difficult it is to erase correlations leads to a nearly complete synthesis and simplification of the known results of asymptotic quantum information theory. As it turns out, surprisingly many of the tasks of interest, from distilling high-quality entanglement to sending quantum data through a noisy medium to many receivers, can be understood as variants of erasure. I'll sketch the main ideas behind these discoveries and end with some speculations on what lessons the new picture might have for understanding information loss in real physical systems.

In an anisotropic limit of the weakly-coupled, 2+1-dimensional non-Abelian gauge theories are equivalent to a collection of integrable 1+1-dimensional quantum field theories. This fact makes it possible to understand confinement near this limit. Using exact form factors, it is possible to study the theory away from the extreme anisotropic limit. The string tension between fundamental color sources is found. Adjoint sources are not confined. Some ideas concerning the isotropic case and the generalization to 3+1 dimensions will be discussed.

We give a communication problem between two players, Alice and Bob, that can be solved by Alice sending a quantum message to Bob, for which any classical interactive protocol requires exponentially more communication.

Theories of physics beyond the Standard Model predict the existence of relativistic strings, either as composite objects, or as fundamental constituents of matter. If they were created in the Big Bang, they would very likely still be present in the universe today. This talk reviews the thirty year history of cosmic strings, and describes the latest work which finds intriguing hints in the Cosmic Microwave Background data that the universe is filled with string.