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


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,