>VITAE:
Matt Leifer completed his Ph.D. at the University of Bristol in 2003 under
the supervision of Prof. Noah Linden (Title: Entangled Quantum Dynamics).
From 20042006 he was a postdoc at the Perimeter Institute for Theoretical
Physics and after a brief stint at the University of Cambridge he began
a second postdoc at the University of Waterloo in 2007. Research interests
include: Foundations of Quantum Theory, Quantum Bayesianism, Algorithms
for simulating manybody quantum systems and Entanglement theory. 


After briefly reviewing the convex sets framework, I will
show that an exponentially secure bit commitment protocol exists in any
theory within the framework that does not permit entangled states
[1]. Combined with our earlier results on broadcasting [2],
this provides a complete generalization of the theorem proved by Clifton,
Bub and Halvorson that was aimed at characterizing quantum theory in terms
of information theoretic constraints [3].
Their theorem was proved in the context of C*algebraic theories, but
unfortunately in the more general context of convex sets, the same axioms
do not imply anything particularly close to quantum theory. If time permits,
I will discuss a conjecture about the set of theories that do not permit
bit commitment.
[1] H. Barnum, O. Dahlsten, M. Leifer
and B. Toner, Nonclassicality without entanglement enables bit commitment
(2007), submitted to IEEE Information Theory Workshop 2008, arXiv version
to appear soon.
[2] H. Barnum, J. Barrett, M. Leifer and
A. Wilce, Generalized NoBroadcasting Theorem (2007), to appear in Phys.
Rev. Lett., arXiv:0707.0620
[3] R. Clifton, J. Bub and H. Halvorson,
Characterizing quantum theory in terms of informationtheoretic constraints,
Foundations of Physics 33, 15611591 (2003), arXiv:quantph/0211089v2
