Talks

The theory of strong interactions is an elegant quantum field theory known as Quantum Chromodynamics (QCD). QCD is deceptively simple to formulate, but notoriously difficult to solve. This simplicity belies the diverse set of physical phenomena that fall under its domain, from nuclear forces and bound hadrons, to high energy jets and gluon radiation. In this talk I show how systematic limits of QCD, known as effective field theories, provide a means of isolating the essential degrees of freedom for a particular problem while at the same time supplying a powerful tool for quantitative computations. The adventure will take us from the fine structure of hydrogen, to weak decays of B-mesons, to the behavior of energetic hadrons and jets in QCD.

In the future it may be possible to observe the CMB radiation at very low frequencies. I review the origin of the signal from 21cm absorption by dark-age gas and explain the huge potential for observational cosmology. I summarise recent work on theoretical expectations for the observable power spectrum, including discussion of Hubble-scale perturbations, the effects of perturbed recombination and non-linear evolution.

Sensitive information can be valuable to others - from your personal credit card numbers to state and military secrets. Throughout history, sophisticated codes have been developed in an attempt to keep important data from prying eyes. But now, new technologies are emerging based on the surprising laws of quantum physics that govern the atomic scale. These powerful techniques threaten to crack some secret codes in widespread use today and, at the same time, offer new quantum cryptographic protocols which could one day profoundly alter the way we safeguard critical information. Quantum cryptography, quantum physics, Daniel Gottesman, cryptography, one-time pad, RSA, encryption, public key, decryption, private key, quantum computer, qubit, shor\'s algorithm, quantum key distribution, QKD

Consider a discrete quantum system with a d-dimensional state space. For certain values of d, there is an elegant information-theoretic uncertainty principle expressing the limitation on one's ability to simultaneously predict the outcome of each of d+1 mutually unbiased--or mutually conjugate--orthogonal measurements. (The allowed values of d include all powers of primes, and at present it is not known whether any value of d is excluded.) In this talk I show how states that minimize uncertainty in this sense can be generated via a discrete phase space based on finite fields. I also discuss some numerically observed features of these minimum-uncertainty states as the dimension d gets very large.