Talks

Do ideas about information and reality inspire fruitful new approaches to the hardest problems of modern physics? What can we learn about the paradoxes of quantum mechanics, the beginning of the universe and our understanding of black holes by thinking about the very essence of information? The answers to these questions are surprising and enlightening, but also controversial. The topic of information within physics has involved some of the 20th century\'s greatest scientists in long-running intellectual battles that continue to the present day. In this special debate, hosted by the CBC\'s Bob McDonald of \'Quirks and Quarks\', you will enjoy a lively discussion between four prominent physicists who have thought long and hard about these questions. information, quantum mechanics, quantum cryptology, entropy, everything computes, properties equals information, uncertainty principle, quantum computer, hologram, black hole, event horizon, coherence, Schrodinger, interference and predictability, quantum state, teleportation, entanglement

Warped backgrounds in string theory are useful tools for building phenomenological models of early universe cosmology and particle physics. In particular, warped backgrounds play an important role in constructing viable models of brane inflation and can help explain the presence of hierarchies in particle physics. One interesting feature of warped models is that subtle differences in the warped geometry can lead to significant differences in observational signatures in the CMB and at the LHC that can be used to distingiush different models. In this talk, I will discuss recent work in distinguishing different warped geometries through CMB and LHC observations.

The spacetime or histories approach is a whole attitude to quantum mechanics in which histories are fundamental rather than states. In this talk we will review a suggested dynamics and a suggested interpretation in this framework, phrasing the dynamics of stochastic collapse models in the histories language then proceeding to explore a new realist interpretation suggested by Rafael Sorkin and examining its perspective on the Kochen-Specker result.

We describe the measurement statistics of the balanced homodyne detection scheme in terms of the moment operators of the associated positive operator measures. In particular, we give a mathematically rigorous proof for the fact that the high amplitude limit in the local oscillator leads to a measurement of a rotated quadrature operator of the signal _eld. Using these results, we also show that each covariant phase space observable can be measured with the eight-port homodyne detector.

With the discovery of many new satellite galaxies, in recent years our understanding of the Milky Way environment has undergone a dramatic transformation. I will discuss what these discoveries are telling us about galaxy formation and the nature of dark matter itself. Issues I will focus on include: identifying the least luminous dark matter halo in the Universe, distinguishing between warm and cold dark matter, and indirect dark matter detection.

In the first part of the talk we introduce a technique to compute large scale correlations in LQG and spinfoam models. Using this formalism we calculate some components of the graviton propagator and of the n-points function. In the second part we apply the ideas suggested by LQG to the black hole interior . The result of the quantum analysis is that the classical singularity disappears in loop quantum gravity. Solving the semiclassical Einstein equation of motion we obtain a metric regular and singularity free in contrast to the classical one. By using the new metric we calculate the Hawking temperature, entropy and we study the mass evaporation process.

One of the most significant questions in quantum information is about the origin of the computational power of the quantum computer; namely, from which feature of quantum mechanics and how does the quantum computer obtain its superior computational potential compared with the classical computer? In my talk, I address this open question more concisely through the study of measurement-based quantum computer, in which all the quantum resource is attributed to entanglement since computation is carried through its consumption by local measurements. I also show a simple model of the phase transition of quantum computer occurring at some threshold, below which the quantum computer comes to allow an efficient classical simulation in accordance with an exponential drop in the amount of entanglement.

Quantum fields in the Minkowski vacuum are entangled with respect to local field modes. This entanglement can be swapped to spatially separated quantum systems using standard local couplings. A single, inertial field detector in the exponentially expanding (de Sitter) vacuum responds as if it were bathed in thermal radiation in a Minkowski universe. Using two inertial detectors, interactions with the field in the thermal case will entangle certain detector pairs that would not become entangled in the corresponding de Sitter case.The two universes can thus be distinguished by their entangling power.