Over the years they worked on the the
thermodynamics of computing that is the
amount of energy required to compute
and then I got involved in quantum
information quantum computing
all what additional things can you do
with information
when you use information
carriers
that her small enough to obey quantum
laws
and this grew into a big field it
included
quantum cryptography and now a kind of
re casting of the whole theory of information
and computing
on quantum foundations I've really got
interested in it
from a college classmate of mine
Stephen Wiessner who made some of the
most fundamental discoveries in this
field back
in the round early nineteen seventies
he had a paper that didn't get published
for thirteen years
that had the well
the it had to inventions in it which
were
one of them was money that's
physically impossible to counterfeit
are and the other one was
a way of sending two messages so that
the processor reading one of them spoils
the other
talking to this about this Weisners
discovery which I was aware of
with Gilles Brassara is what got us
to figure out that you can use it for
quantum key distribution
I was in Puerto Rico and San Anton Puerto Rico
swimming in the ocean so there I was just
swimming and minding my own business
when a complete strangers swims up to me
and tells me that
he knows how to use quantum mechanics to
make bank notes
that would be impossible counterfeit
kind of surprising
I'm so I listen to him politely
and by the time we had swam back to shore
I had found a way to improve this idea
this stranger was Charles Bennett
and and I had been his first victim
but somehow was the first person to pay attention
on that day he told me about
ideas and his friend Steven Weisner
oh you probably said I
swam out to him in the water and I told
him about this
Weisners work yes
well that's pretty much what
happened
and you see at that point I was not a, I
was a physicist with not
much training in computer science so he
brought up
all these these ideas that are well
known in computer science
but we're in cryptography which was also
familiar with
that I had not been familiar with like
the kind of cut and choose idea where
in order to prove that I know something
I produced two things and
but you have to choose which one I'm
going to open up and if I'm
cheating then then if they open up the
wrong one I'll get caught out
so formal ways of doing that and they
fed into this into this stuff that we
did
afterwards and is in fact the first idea
was he said oh
the trouble with these quantum this
quarter money is that you have to in
order to read it you have to
to be the bank you have to know the
secret in it
wouldn't it be nice if you could read
it without knowing the secret and
he thought of a way of combining the
Wiessner quantum money
with a public key cryptography
would do that it was not there
completely random occurrence
we were both there for a symposium
and the annual foundations of computer
science
symposium known as FOX which took place in
'79 in Puerto Rico and he had seen the
program
and he knew it I was going to talk about
cryptography on the last day
he had spotted me from my name tag
at the opening reception but waited till
we were in the water not wearing my name tag
before addressing me
