Events

QUANTUM + Pop Culture

“Quantum physics” has taken its position with “rocket science” in pop culture as a shorthand for frighteningly complicated science. Quantum physics has also taken on a sort of magical connotation in fiction, with features like entanglement, superposition, and tunneling spurring imagination. But where does the science draw the line? How much is joyful speculation, and how much is disregard for reality? And if it’s always seen as either magical or scary, how does that affect the perception of quantum science?

Henry Yuen, University of Toronto

An outstanding open question in quantum information theory concerns the computational complexity of nonlocal games. in a nonlocal game, a classical verifier interacts with multiple players that cannot communicate, but are allowed to share entanglement. In a recent breakthrough result, Slofstra showed that the following problem is undecidable: given a nonlocal game, is there a quantum strategy for the players to win with probability 1?

Neutron whispering gallery

Dr Valery Nesvizhevsky, European Centre for Neutron Research, Institut Laue-Langevin

The "whispering gallery" effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for atoms and neutrons. For matter waves, it would include a new feature: a massive particle would be settled in quantum states, with parameters depending on its mass. In 2010, we observed the quantum whispering gallery effect for cold neutrons and since then continue increasing the precision in these experiments.

Methods for parallel quantum circuit synthesis, fault-tolerant quantum RAM, and quantum state tomography

PhD Candidate: Olivia Di Matteo
Supervisor: Michele Mosca

Thesis available from the Science graduate office, PHY 2013.

Oral defence in QNC B204.

Justin Thaler, Georgetown University

The quantum query complexity of a function f measures how many bits of the input a quantum computer must look at in order to compute f. 

PhD Seminar: Olivia Di Matteo

Quantum random-access memories (qRAM) are required by numerous quantum algorithms. In many cases, qRAM queries are the limiting factor in the implementation of these algorithms. In the limit of a large number of queries, there will be a massive resource overhead, as in this regime it is not possible to bypass the need for active error correction. In this talk, I will present our work towards quantifying this overhead. We will explore a variety of different qRAM circuits designed to query classical bits in superposition.

Stacey Jeffery, QuSoft, Research Centre for Quantum Software

A random walk on a graph, P, with marked vertex set M, finds a marked vertex using a O(HT(P,M)) steps of the walk, where HT(P,M) is the hitting time. Previous quantum algorithms could detect the presence of a marked vertex in O(sqrt{HT(P,M)}) steps, or find a marked vertex in O(sqrt{HT(P,M)}) steps if M contained at most one vertex, but the case of finding in the presence of multiple marked vertices was left as an open problem.

Arthur Mehta, IQC

Non-local games, also known as interactive proof systems, have long been an important area of study for mathematicians, physicists and computer scientists. Starting with the famous CHSH game in 1969, it has been known that non-local games are also an ideal area to explore the differences between quantum and classical behaviour. This has motivated the study of the area of non-local games for people working in quantum information.

Alvaro Alhambra, Perimeter Institute

Heat-Bath Algorithmic Cooling is a technique for producing pure quantum systems by utilizing a surrounding heat-bath. Here we connect the study of these cooling techniques to the resource theory of athermality, enabling us to derive provably optimal cooling protocols under a variety of experimental restrictions on the available control.

Rescheduled from Tuesday, February 12