In October of 2019, Google published a
paper in the journal Nature confirming
that they had achieved something called
quantum supremacy with their prototype
quantum processor. And the world went
kinda nuts. But what does quantum
supremacy actually mean? And how does it
affect the future of our world's
computing as a whole?
*Intro Music*
Quantum supremacy is a very specific
term. Simply put, it means that a quantum
computer has successfully run a
computation faster than a classical
computer ever could. J: But that's different
from the capacity to solve something
that's useful, or to even solve a broad
class of problems. And I think that's
that's the a source of confusion. If
someone hears supremacy, that means it's
the best of everything, right? This is a
specific case of terminology. Maybe it's—
often, if you go to
conferences people feel it's kind of an
unfortunate moniker, but it's one that
stuck and it means this very specific
thing, which is that you built a system
you were able to control to do something
in a reliable way that was hard to
compute. It's specifically not a useful
calculation, we don't know how to make
use of that probability distribution
that was produced—at this point—
and so you know that's a pretty
big difference from, 'quantum computing
is solved ,now on to exponential growth
or whatever.' M: Now, at this point you might
be saying 'what is quantum computing? and
how does it work?'
Funny you should ask! We actually now
have a deep dive into all of that out
right now, which you can watch here. But
in brief–classical computing is the kind
of computing that you and I are used to,
like on our phones and our laptops and
stuff. It's binary computing, which means
it uses a system of on or off signals to
encode data–that's the ones and zeros
that you may sometimes see in the
hacking scenes of some spy movies. A one
and a zero together is called a bit in
classical computing and it's basically
like a little packet of information. On
the other hand... J: Quantum computing is the
idea of doing a computation using the
laws of quantum mechanics and they're a
little different than classical
mechanics. The main difference being that
quantum systems can be in more than one
state at the same time. M: Again, it's pretty
complicated, so if you want even more
detail then go check out our other video
on it here. But in the meantime, has the
world reached quantum supremacy? Like,
is there a machine out there that can
perform a calculation faster than a
classical computer? Technically...yes. J: I'd
characterize it as the latest
high-profile advance in making ever more
sophisticated quantum computing devices
or quantum experiments. What they were
able to demonstrate is, I think
convincingly, that yes—they were able to
construct a system that had a large
enough number of quantum degrees of
freedom with sufficient control to
prepare a state that was extremely
difficult to calculate, to basically
predict, by simulating the
quantum computer ahead of time. M: So they
successfully built a system that
answered a question about quantum
mechanics faster than a classical
computer ever could. And that kind of
makes sense, because the quantum
processor itself is a quantum system so
it's able to answer questions about
quantum mechanics. But all of this is
different from it being a computer
that's truly able to perform useful
calculations or to do all of the things
that we think quantum computers might
eventually be able to do, like change the
way we think about cryptography. That's
not to say that this advancement isn't
really cool and informative, but y'know
it's maybe not like, totally paradigm
changing. It's more of kind of an
arbitrary benchmark that may or may not
mean much depending on the task you
asked the quantum computer to do. J: I think
they demonstrated some real advances in
this quantum-classical interface and
that's essential for arguing that you
can scale a quantum computer to a larger
thing, it needs to be able to scale
according to simple rules and so that
was, I think of laudable outcome
of that of that work. M: So yes, a team has
demonstrated quantum supremacy. But that
may not mean what it sounds like. Yeah,
it's a step forward in the exciting
field of quantum computing...but we're
still a long way from a universal
quantum computer or even a quantum
computer that could be anything more
significant than like, a really cool
quantum physics experiment. If you want
to know all about the ways that
Livermore is working toward that goal of
realizing something closer to a
universal quantum computer, then let us
know down in the comments below, and
we'll make sure to make that video. If
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Inside the Lab by checking out the full
playlist and thanks for watching.
I'll see you next time.
