Let me briefly describe the difference between
a quantum computer and a regular computer,
at some level.
In a regular computer, you've got ones and
zeros, which you store in binary form and
you manipulate them and they do calculations.
You can store them, for example, in a way
that at least I can argue simply.
Let's say you have an elementary particle
that's spinning.
If it's spinning, and we say it's spinning,
it's pointing up or down depending upon whether
it's spinning this way or this way, pointing
up or down.
And so, I could store the information by having
lots of particles and some of them spinning
up and some of them spinning down.
Right?
One's and zero's.
But in the quantum world, it turns out that
particles like electrons are actually spinning
in all directions at the same time, one of
the weird aspects of quantum mechanics.
We may measure, by doing a measurement of
an electron, find it's spinning this way.
But before we did the measurement, it was
spinning this way and this way and that way
and that way all at the same time.
Sounds crazy, but true.
Now that means, if the electron's spinning
in many different directions at the same time,
if we don't actually measure it, it can be
doing many computations at the same time.
And so a quantum computer is based on manipulating
the state of particles like electrons so that
during the calculation, many different calculations
are being performed at the same time, and
only making a measurement at the end of the
computation.
So we exploit that fact of quantum mechanics
that particles could do many things at the
same time to do many computations at same
time.
And that's what would make a quantum computer
so powerful.
One of the reasons it's so difficult to make
a quantum computer, and one of the reasons
I'm a little skeptical at the moment, is that
- the reason the quantum world seems so strange
to us is that we don't behave quantum mechanically.
I don't -- you know, you can - not me, but
you could run towards the wall behind us from
now 'til the end of the universe and bang
your head in to it and you'd just get a tremendous
headache.
But if you're an electron, there's a probability
if I throw it towards the wall that it will
disappear and appear on the other side due
to something called quantum tunneling, okay.
Those weird quantum behaviors are manifest
on small scales.
We don't obey them - have those behaviors
'cause we're large classical objects and the
laws of quantum mechanics tell us, in some
sense, that when you have many particles interacting
at some level those weird quantum mechanical
correlations that produce all the strange
phenomena wash away.
And so in order to have a quantum mechanical
state where you can distinctly utilize and
exploit those weird quantum properties, in
some sense you have to isolate that system
from all of its environment because, if it
interacts with the environment, the quantum
mechanical weirdness sort of washes away.
And that's the problem with a quantum computer.
You want to make this macroscopic object,
you want to keep it behaving quantum mechanically
which means isolating it very carefully from,
within itself, all the interactions and the
outside world.
And that's the hard part, Is isolating things
enough to maintain this what's called quantum
coherence.
And that's the challenge and it's a huge challenge.
But the potential is unbelievably great.
Once you can engineer materials on a scale
where quantum mechanical properties are important,
a whole new world of phenomenon open up to
you.
And you might be able to say - as we say,
if we created a quantum computer, and I'm
not - I must admit I'm skeptical that we'll
be able to do that in the near-term, but if
we could, we'd be able to do computations
in a finite time that would take longer than
the age of the universe right now.
We'd be able to do strange and wonderful things.
And of course, if you ask me what's the next
big breakthrough, I'll tell you what I always
tell people, which is if I knew, I'd be doing
it right now.
