Quantum Institute: Visitor Schedule

The Quantum Lunch is regularly held on Thursdays in the Theoretical Division Conference Room, TA-3, Building 123, Room 121.
For more information, contact Diego Dalvit.
To add your name to the Quantum Lunch email list, contact Charlotte Lehman

Thursday, May 6, 2010
12:30 PM - 2:00 PM

Speaker: Graeme Smith (IBM)

Technical Host: Jon Yard

TOPIC: When Quantum Mechanics Meets Time Machines

Abstract
Physicists and science fiction writers have long been interested in time travel, wherein a person or object travels backward in time to interact with a younger version of itself. The many studies of such closed timelike curves have led to the general conclusion that, while conditions for their creation may not arise in typical astrophysical or cosmological settings, in principle there seems to be no barrier to their existence. That said, it is not entirely clear how to do quantum mechanics in the presence of closed timelike curves.

In this talk I’ll discuss some of the different proposals for quantum mechanics with closed timelike curves. I’ll illustrate what the world is like under some of these models, using simple quantum computations as illustrative examples of interaction and change. Because time-travel induces nonlinear evolution in most cases, there are a lot of subtleties that don’t come up in linear quantum mechanics. This leads to questions about what it means to “compute", “distinguish", and even “choose".