Lawrence Krauss: Quantum Computing Explained
Δημοσιεύτηκε στις 26 Αυγ 2013
Lawrence
Krauss describes quantum computing and the technical obstacles we need
to overcome to realize this Holy Grail of processing.
Lawrence
Krauss: 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.
Directed / Produced by Jonathan Fowler and Elizabeth Rodd
Krauss describes quantum computing and the technical obstacles we need
to overcome to realize this Holy Grail of processing.
Lawrence
Krauss: 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.
Directed / Produced by Jonathan Fowler and Elizabeth Rodd
Κατηγορία
Άδεια
- Τυπική άδεια YouTube
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου