[FABIO] In principle, we can imagine that we
could use quantum computers for
designing more effective drugs.
[LISA] Welcome to Nano Matters, the podcast that
explores specific examples of
nanotechnology. I'm Lisa Friedersdorf, Director of the National Nanotechnology
Coordination Office. Here with me today
is Fabio Pulizzi, editor of Nature
Nanotechnology. So Fabio, we're hearing
more and more about quantum information
and quantum computation. What is a
quantum computer and how is it different
from a regular computer that we're all
used to?
[FABIO] So in the classical computer you
have a number of single elements, of
fundamental elements, that we call bits
and each of them normally takes a value
only of 0 or 1. And each bit for example a
classical way which a bit is realized is
through a very small transistor which
can be either not passing in the current
or past in a finite current. That would
represent the two states. Now in a
quantum computer you still have bits
which in this case are called qubits,
which also assume different, precise
values, but they can also have a value
which is a superposition between the two.
So in the case of transistor, although
that's not really a quantum system, but
for analogy that would be a state
which is half off - half zero current - and
half current passing. The most
important thing is that when you have
a range of qubits, they interact with
each other. So in a classical computer,
everything every information that is
stored and every operation with this
information that is stored is made, it's
made sequentially. So one after the other.
So it can be very fast, but the speed
does not depend on the intrinsic
nature of the of the element, but more on
the size and on the way they interact and
the way in which they can be addressed
with real external means. In quantum
computation, the qubits are actually
acting as an ensemble and the operation
occurs in parallel. And so it can be much
more efficient and much faster in
certain cases.
[LISA] Why do we want a quantum
computer? What can it do that our normal
computers can't already do?
[FABIO] Well there are
several types of applications that a
quantum computer would be able to do
faster or more efficiently. When I say
faster it could even be a situation in
which a classical
computer would take an infinite time to
do and a quantum computer could do in a
finite time. Perhaps the most interesting
is the idea that we can use quantum
computers for quantum simulations. A
simulation in general is used when we
want to understand a system in nature
and we would study the system and then
we can, through a computer, simulate its
behavior. Time, for example. Now the
reality is that nature is by default a
quantum system especially at the very
low scale. So if we want to simulate
something that happens to a
natural system in the very low scale,
we'd have to approximate this quantum
nature with a classical nature and then
whatever we come out with will only be
an approximation of it. With a quantum
computer, we could in principle use what
we have to simulate a quantum system in
a much more natural way because the
quantum computer follows the same laws
of quantum mechanics that the system is following.
[LISA] How is nanotechnology related
to quantum computing?
[FABIO] Well nanotechnology can offer systems
that could be very good as qubits. It's as
simple as that. It's the simple way in
which I see it. So let's remember that a
qubit is simply a system. It can be any
system that can assume two fundamental
values. It can be 0, 1, it can be -1, 1, it
can be the position of an electron in
space, it can be the charge of an
electron inside a small crystal, the
important thing is that the systems that
nanotechnology can provide, quantum dots
for example, they have the advantage they
can be embedded into solid-state devices.
And that makes it a lot easier to
address them by electrical means, by
optical means. In principle, it can also
make it easier to be used in conditions
that are easily accessible. For example,
at temperatures which are not
particularly cold for which we have to
use very sophisticated refrigeration
systems or very high vacuum systems. So
at the moment the most successful
results that we have in quantum
computers - in fact we can say that some
time to computers already exist -
they are made with systems that require
a lot of cost a lot of effort. Probably
the most valiant examples are the
so-called quantum computers that exist
made out of superconducting qubits or of
ions in vacuum. So the two require,
respectively, very cold temperatures and
very high vacuum, So hopefully, with
nanotechnology we will be able to
achieve systems that are much more
accessible even on tabletop.
[LISA] So you've mentioned that there are some quantum computers in that they operate at either
very low temperatures or in a vacuum or
they're specialized systems and there's
been proof of concepts and a number
of announcements made by companies that
they have developed quantum computing, but not in as you mentioned maybe on
a desktop or for more general purpose.
How far do you think we are from
realizing quantum computing in a broader
sense?
[FABIO] Well that's a very hard question
to answer because the reality is that if
we make the parallel with classical
computers, the first thing I think about
is that we are used to documentaries or
movies when we see computers in a -
several decades ago they would fill an
entire room and would require a lot of
attention, a lot of energy, and their
power would be not even fairly
comparable to devices that we have now
and that we can put in our pockets and
that has taken some decades. So the speed
at which things evolve these days, one
could think that it would take a lot
less, but then again quantum mechanics
quantum physics are different from
classical physics so it's very hard to
know. I think an important point to
consider is whether  do we really need
something that is used on a broader
scale, for example that we can have on
our desk or in our pocket. At the moment
I can't see why we would want that, but
then again, those who invented the first
computer certainty we're not thinking
about desktop computers or laptops or
iPads or iPhones. So that's not for me to
tell.
[LISA] So where do you think this
technology will have the most
significant impact?
[FABIO] From what I can see
now and particularly from what I hear
experts in the field saying, I have to go
back to quantum simulation. One of the
things that people say often is that in
principle we can imagine that we could
use quantum computers for designing more
effective drugs. That is one simple
example in the sense that if we think
about drugs as big molecules, which are
governed by quantum mechanics and
quantum physics, having a quantum
computer that allows us to simulate the
properties of molecules at the larger
scale than just two or three would
certainly help us in creating drugs that
could be more effective, that would have
properties that we desire.
[LISA] So Fabio, thank you so much for joining us today. I
think that's been a great discussion of
quantum computing, what it is and why
it's important. Do you have any closing
thoughts that you'd like to share with
our listeners?
[FABIO] Well maybe one thing I'd
like to say is that when we think about
quantum computing particularly quantum
information but quantum computing
particularly, the first thing we think
about is the final goal which is
creating this quantum computer. And
that's great, that's fine. But what I
think is the greatest thing is that that
drive towards creating an actual product
in fact gives us the opportunity to look
at the fundamentals of quantum mechanics.
Yes it would be great if one day we have
a very efficient quantum computer, but
what we will learn on the way
will perhaps reveal to be more important
than the final product.
