Demonstrating Quantum Supremacy
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Demonstrating Quantum Supremacy

HARTMUT NEVEN: The tantalizing
promise of quantum computers is that they can do certain
tasks exponentially faster than classical machines. And the quantum
supremacy experiment is proof that this
is indeed the case. MARISSA GIUSTINA: The
word quantum computer is a little bit
misleading because it sounds like a computer, and
when people think of computer, they think of a
phone or a laptop. The truth is the
phone and the laptop and even a very powerful
supercomputer all operate according to the
same fundamental rules, and a quantum computer is
fundamentally different. JOHN MARTINIS: The classical bit
stores information as a 0 or 1, and a quantum bit can be both
a 0 and 1 at the same time. If you have two quantum
bits, then there are four possible states that
you can put in superposition. With three qubits, it’s eight. Four qubits, it’s 16. It grows exponentially. HARTMUT NEVEN: The nice
thing about quantum supremacy is that this is a very
well-defined engineering milestone. SERGIO BOIXO: In a
nutshell, what we’re trying to do is we’re trying to
show that experimental quantum computers can surpass the best
supercomputers in the world. MARISSA GIUSTINA: To actually
demonstrate quantum supremacy, we have these three steps. First, pick a circuit. Second, run it on
the quantum computer. Third, simulate what
the quantum computer is doing on a
classical computer, and we gradually increase the
complexity of that circuit. At some point, it
becomes completely impossible for the classical
computer to keep up. Then we say we have
achieved quantum supremacy. JOHN MARTINIS: We
started building together on the quantum chips
to do this experiment, and then the evolution
of the devices with more and more qubits
and more and more complexity is very much an
iterative process. MARISSA GIUSTINA:
A lot of the work that we put in was
not just these chips but is also the
infrastructure that you need to drive those chips. The cryostats that
we install them in, all of the control electronics,
software, all of this stuff is needed, and it all
has to be developed. SERGIO BOIXO: When the
experiment started, when we were getting data
from the experimentalists, we saw initially a beautiful
straight line corresponding to our predictions. HARTMUT NEVEN: Then
right before we hit supremacy it
dropped much faster, then fell below the threshold
where it needed to be. CHARLES NEILL: And
there’s nothing we can do because we don’t
know how to analyze past that. So everyone’s like,
oh, we’re screwed because it’s getting
really, really bad at large number of qubits. JOHN MARTINIS: It’s
like, well, maybe there’s some really
complex interaction between all the qubits. HARTMUT NEVEN: It turned
out that the reason was rather benign. We calibrated a
little bit better, and then this
problem disappeared. ANTHONY MEGRANT: So there
wasn’t like a, oh, we did it. BRIAN BURKETT: I
think we crossed it, and then it wasn’t clear
that we crossed it, so we crossed it a
little bit further. SERGIO BOIXO: It took me like
a day to realize, hold on. This is actually
experimental data. It’s kind of amazing to see
how well the theory works. HARTMUT NEVEN:
The processor that achieved quantum supremacy is
called the Sycamore processor. JOHN MARTINIS: And it’s parallel
processing 2 to 53 states, which is 10 million billion. And thus that enormous
amount of parallel processing is what gives it the power. SERGIO BOIXO: When we run
small chunks of the computation in the largest super
computer in the world, our estimate is that it
will take thousands of years to complete the
full computation. HARTMUT NEVEN: Technologies
are born this way. Let’s say the space age started
with a satellite orbiting Earth, and it was
not doing much. It was just beeping. JOHN MARTINIS: The big
technical achievement of quantum supremacy was
really dependent on all this young talent who’s
kind of taking this and gotten it to work at a very
technologically capable level. HARTMUT NEVEN: We have reached
a new computational capability. There are certain
computations, the only place in the world where
you can compute those things is our data
center at Google Santa Barbara. JOSH MUTUS: For the
first time, we’re showing that we can solve
a problem that is just infeasible to do on the
biggest computers ever made by civilization. ERIK LUCERO: And
what’s exciting is now we’re ready to turn
this over to the world and say, let’s figure out
what we can do with this. MARISSA GIUSTINA: The
thing that excites me most is building a useful
quantum computer. When we can give a researcher
a tool that is unlike any other and say create, figure out
something cool to do with it, mankind is pretty good at that.


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