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.
Arguably, the most important issue in physics today is trying to unify the twin pillars of modern physics, quantum theory and general relativity, into a single theory known as quantum gravity. This introductory presentation will discuss various aspects of quantum gravity.
I will review the published quasar absorption line constraints on variations in the fine-structure constant, alpha, focusing on the apparent disagreement between those derived from Keck/HIRES and VLT/UVES spectra which have provided evidence for and against alpha variation, respectively. I demonstrate simple yet fundamental flaws in the UVES constraints which preclude reliable comparison with those from HIRES. I will outline our program to obtain a definitive UVES measurement.
We discuss two methods to encode one qubit into six physical qubits. Each of our two examples corrects an arbitrary single-qubit error. Our first example is a degenerate six-qubit quantum error-correcting code. We explicitly provide the stabilizer generators, encoding circuits, codewords, logical Pauli operators, and logical CNOT operator for this code. We also show how to convert this code into a non-trivial subsystem code that saturates the subsystem Singleton bound.
We investigate the strengths and weaknesses of the Spekkens toy model for quantum states. We axiomatize the Spekkens toy model into a set of five axioms, regarding valid states, transformations, measurements and composition of systems. We present two relaxations of the Spekkens toy model, giving rise to two variant toy theories. By relaxing the axiom regarding valid transformations a group of toy operations is obtained that is equivalent to the projective extended Clifford Group for one and two qubits.
The world as experienced by single atoms is radically different from the everyday world we, as gigantic humans, are used to: the laws of quantum mechanics replace the laws of classical physics. Because the quantum realm is alien from our daily experience, many common quantum effects are surprising and unintuitive. To understand the quantum world, it may be better to just start from scratch, as a child might, and develop intuition about the behavior of quantum objects by simply looking at a series of quantum examples rather than trying to analogize with classical physics.