# Video Library

Since 2002 Perimeter Institute has been recording seminars, conference talks, public outreach events such as talks from top scientists 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 and 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.

Accessibly by anyone with internet, Perimeter aims to share the power and wonder of science with this free library.

## Purifying qubits in NMR quantum information processing

Saturday Jun 02, 2007
Speaker(s):

Any implementation of  a quantum computer will require the ability to reset qubits to a pure input state, both to start the computation and more importantly to implement fault-tolerant operations.  Even if we cannot reset to a perfectly pure state, heat-bath algorithmic cooling provides a method of purifying mixed states.  By combining the ability to pump entropy out of the system through a controllable interaction with a heat bath and coherent control of the qubits, we are able to cool a subset of the qubits far below the heat bath temperature.

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## Degradation of a quantum directional reference frame

Saturday Jun 02, 2007
Speaker(s):

In this study, we are interested in the practical question of how many times a quantum directional reference frame (i.e., a spin-J system) can be used to perform a certain task with a given probability of success, under the assumption that the quantum directional reference frame evolves under a map that is covariant under rotations in SU(2). Our main theorem restricts the form of the state of the quantum reference frame as a function of how many times the covariant map was applied to it. Our results are a generalization of the paper of Bartlett el al.

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## Quantum Key Distribution Networks

Saturday Jun 02, 2007
Speaker(s):

Current physical implementations of quantum key distribution (QKD) require communicating parties to be close together.  We will explore methods for allowing parties separated by long distances to communicate by combining many QKD links in a network and discuss the resulting security properties.

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## Towards the Production of Entangled Photon Pairs in Optical Fiber via Four-Wave Mixing

Saturday Jun 02, 2007
Speaker(s):

Previous experiments on the production of entangled photon pairs directly in optical fiber via four-wave mixing (FWM) have used a single pump laser and produced signal and idler photons with similar wavelengths. We will present the first results of our investigation into the production of widely separated entangled photon pairs via FWM in optical fiber using multiple pump lasers also at widely separated wavelengths. This source will have important applications in quantum cryptography and computation.

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## Distributed phase reference schemes for QKD: Explicit attacks and security considerations

Saturday Jun 02, 2007
Speaker(s):

"Distributed phase reference schemes are a new class of protocols for Quantum Key Distribution, in which the quantum signals have overall phase-relationships to each other. This is expected to protect against some loss-related attacks. However, proving the full security of these schemes is a new challenge for theorists, as one can no longer identify individual signals (such as qubits in BB84, for instance), and so the security proof techniques do not apply directly.

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## An Introduction to Decoherence-Free Subspaces

Saturday Jun 02, 2007
Speaker(s):
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## Information Flow in the Heisenberg Picture

Saturday Jun 02, 2007
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## Quantum Mechanics in Phase Space

Saturday Jun 02, 2007

Many authors have proposed what are known as "phase-space" or "classical" representations of quantum mechanics.  A unifying framework is given which illustrates the relationship among these various theories.  Examples relevant to quantum computing will be given.

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## An Introduction to One-Way Patterns

Friday Jun 01, 2007

The one-way measurement model is a model of quantum computation which is intriguing for its' potential as a means of implementing quantum computers, but also for theoretical purposes for the different way in which it allows quantum operations to be described. Instead of a sequence of unitary gates on an array of wires'', operations are described in terms of emph{patterns}, consisting of a graph of entanglement relations on a set of qubits, together with a collection of measurement angles for these qubits (except possibly for a subset which will support a final quantum state).

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## Cluster State Quatum Computing in Optical Fibres

Friday Jun 01, 2007
Speaker(s):

In this presentation I will briefly explain the cluster state model of quantum computing. Then will talk about a scheme that uses polarization and time-bin degrees of freedom of photons in optical fibres for the optical realization of this model. We are currently working on the implementation of this scheme in our lab.

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## Next Public Lecture

### CHAD HANNA: PENNSYLVANIA STATE UNIVERSITY

Wednesday Apr 03, 2019