PIRSA:12110068

What's an unknown POVM, and what does a two qubit state look like?

APA

Pusey, M. (2012). What's an unknown POVM, and what does a two qubit state look like?. Perimeter Institute. https://pirsa.org/12110068

MLA

Pusey, Matthew. What's an unknown POVM, and what does a two qubit state look like?. Perimeter Institute, Nov. 06, 2012, https://pirsa.org/12110068

BibTex

          @misc{ pirsa_12110068,
            doi = {},
            url = {https://pirsa.org/12110068},
            author = {Pusey, Matthew},
            keywords = {},
            language = {en},
            title = {What{\textquoteright}s an unknown POVM, and what does a two qubit state look like?},
            publisher = {Perimeter Institute},
            year = {2012},
            month = {nov},
            note = {PIRSA:12110068 see, \url{https://pirsa.org}}
          }
          

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.