Quantum weak coin flipping with arbitrarily small bias

You are here either because you are reading arXiv:0711.4114 and are looking for updates, or because you have an uncontrollable urge to click on every link you see. In either case, welcome!

My goal is to use this space to keep you up to date on the latest coin-flippingly exciting news: has anyone carefully read this paper? Are there any errors, corrections or updates? Can Canadian coins be used in the protocol?

More seriously, if you find an error or have some constructive criticism, please let me know. Small changes may be posted below, major changes will likely lead to a new archive version.

Updates and News

Nov 27, 2007: Fly, paper, fly.

Nov 28, 2007: The first correction comes from Ben Toner who writes "By the way, I think there's a sign error on page 2308." All those of you who printed out Appendix R, please fix your copy.

Nov 29, 2007: The Quantum Pontiff has sanctified this paper! (or at a minimum has given it free publicity). Obviously, as pontiff Dave had prior knowledge of His intent to allow coin flipping, and I appreciate him not ruining the surprise for the rest of us.

Mar 5, 2008: Here is a potentially interesting conjecture/open-problem that I forgot to include in the paper: One can define matrix monotone functions of order n as those that preserve the ordering of n by n matrices. Similarly, one can define bi-operator monotone functions of order n. These may not form a cone, but one can still try to define a dual cone which should correspond to those quantum protocols that can be run with only an n dimensional Hilbert space for each of Alice and Bob. That is, these may help prove space bounds! I further conjecture that the protocols converging to P^* = k+1/2k+1 are exactly the optimal protocols that can be run with a k+2 dimensional Hilbert space on each side.

Mar 6, 2008: I have now given a couple of talks about this paper. My slides are available: PDF, LaTeX. A recording of the PI talk is also available via PIRSA.

Feb 28, 2014: Aharonov, et al. have a cleaner version of the result: arXiv:1402.7166.