Most of Caltech’s contingent during QIP’s banquet. Not pictured: sword dancers, jug balancers and Gorjan.

A couple of weeks ago, about half of IQI (now part of IQIM) flew from Pasadena to Beijing in order to attend QIP 2013, the 16th annual workshop on quantum information processing. I wish I could report that the quantum information community solved the world’s problems over the past year, or at least built a 2^10 qubit universal quantum computer, but unfortunately, we’re not quite there yet. As a substitute, I’ll mention a few of the talks that I particularly enjoyed and the really hard open problems that they left us with.

The emphases of the talks mainly bifurcated towards computer science versus physics. I was better prepared to understand the talks emphasizing the latter, so my comments will mainly describe those talks. Patrick Hayden’s talk: “summoning information in spacetime: or where and when can a qubit be?” was one of my favorites. To the extent that I understood things, the goal of this work is to better understand how quantum information can propagate forward in time. If a qubit were created at spacetime location S, and then if it were forced to remain localized, the no-cloning theorem would give strict bounds regarding how it could move forward in time. The qubit would follow a worldline and that would be the end of things. However, qubits don’t need to remain localized, as teleportation experiments have pretty clearly demonstrated, and it therefore seems like qubits can propagate into the future in more subtle ways–ways that at face value appear to violate the no-cloning theorem. Patrick and the undergraduate that he worked with on this project, Alex May, came up with a pictorial approach to better understand these subtleties. The really hard open problems that these ideas could potentially be applied to include: firewalls, position-dependent quantum cryptography and to paradoxes concerning the apparent no-cloning violations near black hole event horizons.
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