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.