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.
Heavy-hole spin states have been proposed as a robust qubit candidate. Nevertheless, the coupling of the hole spins to nuclei in the surrounding medium likely limits hole-spin coherence and has, until very recently, been overlooked. We describe the spin decoherence of a heavy-hole in a semiconductor quantum dot, subject to spin echo pulses. We do so both analytically and numerically for an experimentally realistic number (10^4) of nuclear spins.
Quantum Key Distribution is a form of public-key cryptography where the security comes from the unique properties of quantum mechanical systems: entanglement and the no-cloning theorem, rather than computational complexity. With increased adoption of fibre optic networks, it may be possible to implement QKD in parallel with classical data traffic. Many research projects have demonstrated QKD over fibre optic networks at the same wavelengths as existing network traffic.
Development of quantum computing promises, among other things, improvement of scientific computation performance. Indeed, a computer exploiting the proprieties of quantum mechanics would allow for computation power exponentially greater than a classic computer.We develop double lateral quantum dots with micro-magnets to control spin orientation of electrostatically confined electrons. In this talk, an introduction to the mechanisms used in the spin control will be given. Then, methods used to characterize the micro-magnets will be described.
A quantum computer is a computer fabricated using quantum bits (qubits) that uses the quantum properties of matter (entanglement, superposition of states, etc.). Such a computer would allow certain calculations to be done exponentially more quickly than with a classical computer. An electron in a quantum box constitutes a perfect two-level system and can thus be used as a qubit. In my talk, I will give an introduction to lateral quantum dots, their fabrication process and how they can be used as qubits.
Quantum entanglement is a valuable resource in the field of quantum information science and allows one to accomplish many information processing tasks. In quantum transformations an entangled state A can be converted to another state B through local operations assisted by classical communication (LOCC). It has also been demonstrated that there exist entangled states A, B, C such that state A cannot be converted to a state B, but A otimes C can be converted to B otimes C by LOCC, where C is a suitably chosen entangled state acting as the catalyst.
Thermodynamics is, at heart, a probabilistic theory about the state of physical systems. Traditionally, however, our knowledge of systems is modelled implicitly: for instance, it is often assumed that we only have access to a few macroscopic parameters, like the temperature, energy, or volume of a gas, and that all states satisfying those parameters are equally likely.
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.