The Physics Department Seminar Series
presents…
Prof. William Wootters
Why does nature like
the square root of
negative one?
TUESDAY,
JANUARY 26TH
4:00 RECEPTION,
4:15 PRESENTATION
CLEVELAND L3
BIO: William K. Wootters is the Barclay
Jermain Professor of Natural Philosophy
at Williams College in Massachusetts.
He got his BS at Stanford and his PhD at
the University of Texas at Austin—both
degrees in physics—and has been at
Williams since 1982, with sabbatical
appointments at Santa Fe Institute, the
University of Montreal, IBM, Perimeter
Institute, and Kigali Institute of Science
and Technology. Prof. Wootters’ main
areas of research are quantum
information theory and quantum
foundations. He is one of the authors of
the 1993 paper showing the theoretical
possibility of quantum teleportation, and
he has done research on the quantitative
theory of entanglement and on phasespace representations of quantum states.
ABSTRACT: Quantum mechanics is a
probabilistic theory, but the way we
compute probabilities in quantum
mechanics is quite different from what
one would expect from, say, rolling dice
or tossing coins. To get a quantum
probability, we first compute a complexvalued probability amplitude and then
square its magnitude. I begin this talk by
looking for a deeper explanation of the
appearance of probability amplitudes, or
“square roots of probability,” in the
physical world. It turns out that one can
find a potential explanation—it is based
on a principle of optimal information
transfer—but the argument works only if
the square roots are real rather than
complex. I then discuss a few of the ideas
people have put forward to try to
understand why nature favors complex
amplitudes. At present no such idea has
gained wide acceptance, but the effort to
answer this question has produced
insights into the structure of quantum
theory.