well I'm very interested in quantum,
computers what they can do,
how we'll build them, how we'll make them
work, but actually my background
is in theoretical particle physics it's a
subject I still love
but back in the nineteen nineties I got
very excited
when I first learned about
quantum computing and the idea that
we would be able to solve problems with
quantum computers that we really
couldn't ever hope to solve with ordinary
digital computers and
I eventually changed the direction my
research because I got so interested in
that subject
I think I got interested because we often
are a bit baffled and fascinated in
physics by
the difference between classical physics
and quantum physics
and I felt that looking at physics
from the point of view of how information
gets stored and processed
gave us new insights into the difference
between systems that are classical
and systems that are quantum and I think
those insights although part of the
reason they're interesting is because
they may lead the way
to new technologies they're also useful
because they give us new perspective on
problems that physicists are interested in
and for fundamental reasons really
important differences between
information that's carried by ordinary
systems like
in digital computers today and
information carried by
quantum systems and probably the most
important distinction between classical
and quantum has to do with
the nature the correlations among the
parts of a system when
quantum systems are correlated with one
another with we say they're entangled
and entanglement is different from the
correlations that we normally encounter
in our everyday lives imagine we have a
book it's a hundred pages long
and if it were an ordinary classical
book you could read one of the pages and
then you'd know one percent of
the content of the book and if you read
another page you know another one
percent of the content
but if it's a quantum book if it's encoded in
a state a quantum system a typical
highly entangled quantum book
would have the property that if you look
at the page is one at a time you learn
almost nothing about the content of the
book
on each page you would just see random
gibberishand that's because the information
that's carried in that
quantum system that quantum book it's
not
encoded in the individual pages it's
almost entirely carried
in the correlations among the pages
so if you wanted to read that book
you would have to make a collective
observation
on many pages at once that's
completely different from information in
the classical world
so even if we have all the information
that it's possible to have about the content
of the book
if we look at just part of it but we see
is just random junk
classical systems we have a complete
description of the whole system then we
also have a complete description of its
parts because if you tried to
characterize
or describe all those correlations among
the parts
of a quantum system using ordinary
classical data
you would need an enormous amount 
classical information to completely
describe all at the correlations
you would need
many more numbers than the number of
atoms in the visible universe
so you'll never be able to write down the
content of a relatively short quantum
book
in terms of ordinary classical
information
it's kind of an amazing thing so there's this
quantum world out there and it somehow
has these
extraordinary resources that it carries
which are much different from many
resources we encounter and
ordinary experience and would like to
learn how to harness that
and to use it to our advantage.
