PIRSA Logo


PERIMETER INSTITUTE RECORDED SEMINAR ARCHIVE

PIRSA:12110068  ( MP4 Medium Res , MP4 Low Res , MP3 , PDF ) Which Format?
What's an unknown POVM, and what does a two qubit state look like?
Speaker(s): Matthew Pusey
Abstract: If probabilities represent knowledge, what is an "unknown
probability"? De Finetti's theorem licenses the view that it is simply a
convenient metaphor for a certain class of knowledge about a series of
events. There are quantum versions for "unknown states" and "unknown
channels". I will explain how "unknown measurements" can be rehabilitated
too.

I will then move to a totally different topic. The Bloch sphere is handy
for representing qubit states, but the equivalent for two qubits is
15-dimensional! I will advocate instead drawing the set of states that Bob
can steer Alice to, the "steering ellipsoid". I will show how entanglement
and discord look from this perspective, and outline a geometric
classification of separable two qubit states.
Date: 06/11/2012 - 3:30 pm
Valid XHTML 1.0!