Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres. Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities. Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA). PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.
We can prove that for certain problems, quantum computers do better than classical computers. I will introduce the query complexity framework, which lets us compare classical and quantum computers, and then describe a problem where quantum computers do better than classical. The problem I will discuss is evaluating boolean trees with a promise on the input.
By exploiting the properties of quantum mechanical systems, two parties can achieve cryptographically secure communication in a manner not possible in a purely classical world, through the process of quantum key distribution. In this talk, I will briefly introduce the field of cryptography and explain one of the most fundamental applications of quantum mechanics to cryptography.
Our understanding of the physical world at the most fundamental level is based on two theories: quantum theory and general relativity. They are impressively successful but only when each is considered on its own. In situations where both play a role, we are reduced to puzzles and absurdity. Hence the search for a quantum theory of gravity, the currently missing theory that will work sensibly in exactly these situations. To the great frustration of researchers in this field, candidate quantum theories of gravity tend to produce more puzzles instead of answers.
I present a proposal, originally motivated by a result in graph theory: the entropy function of a density matrix naturally associated to a simple undirected graph, is maximized, among all graphs with a fixed number of links and nodes, by regular graphs.I recover this result starting from the Hamiltonian operator of a non-relativistic quantum particle interacting with the loop-quantized gravitational field and setting elementary area and volume eigenvalues to a fixed value.
The vacuum polarization effects in superstrong Coulomb and laser fields are considered from the point of view of the generalized quantum dynamics formalism. The vacuum decay time in superstrong electromagnetic field is discussed.
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In this talk I will discuss an alternative to infation models, namely non singular bouncing models.Their advantage is to supress both the transplanckian problem and the big bang singularity. It also gives a scale invariant power spectrum in the case of amatter bounce.First we will study a toy model, the non singular matter bounce. Then we will try to see what is the effect when we add upradiation through a gauge fields. To do that we add up a coupling term between the scalar fields and the gauge fields to see if it destroys the bounce or not.
(n+1)-dimensional Lifshitz spacetime is deformed by logarithmic expansions in the way to admit a marginally relevant mode in which z is restricted by n=z+1. According to the holographic principle, the deformed spacetime is assumed to be dual for quantum critical theories, and then thermodynamics of generic black holes in the bulk describe the field theory with a dynamically generated momentum scale $Lambda$. This is a basically UV-expanded theory considered in higher dimensions of the Lifshitz holography from the previous works.
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