How It Works - UK (2020-02)

http://www.howitworksdaily.com How It Works 027

DID YOU KNOW? Over 17 million experiments were run through IBM’s quantum computers in 2019

How significant is

Google’s breakthrough?

It’s a technical next step, but it’s not

necessarily as significant as some people

think. What Google has done is solved an

academic problem – one that is entirely

useless in a practical sense. It’s a problem

that’s chosen w ith one thing in mind:

whether a quantum computer can do

something a conventional computer can’t.

So why are we talking about it?

Google’s achievement demonstrates that

quantum computers are not like nuclear

fusion, which a lot of people often say is ten

years away, but never actually arrives.

When I started 20 years ago, people were

ver y sceptical. Most of my colleagues rolled

their eyes at me when I said I was going to

build a quantum computer. That’s because

it’s unbelievably hard to control the

quantum effects of atoms. So what Google

has achieved is still really nice, as it’s

demonstrated master y of manipulating 53

qubits. That’s a big milestone.

When do you think quantum

computing will come into its own?

Quantum computing w ill likely follow the

same development path as conventional

computers. In the 1940s, conventional

computers decided World War II by

breaking the German Enigma code.

However, while they were good for a

particular task, they couldn’t tell you

train times, handle word processing or

play v ideo games. It was another 40 to 50

years until we used them for literally

ever y thing. It’s a gradual process. Quantum

computers now are probably approaching

those in the 1940s. In the next five years,

these machines w ill be able to solve one

particular practical problem.

Prof Winfried Hensinger of

the University of Sussex

puts Google’s achievement

into perspective

“Quantum

computers now

are approaching

those in

the 1940s”

qubits, they could hold four values at once: 1-0,

0-1, 1-1 and 0-0. As the number of qubits grow, a

quantum computer ver y quickly becomes more

powerful than a conventional one, so it can

process information in a fraction of the time.

While Fey nman prov ided a blueprint for how

the technolog y could work, actually building a

quantum computer proved much harder. Qubits

are made from indiv idual atoms or subatomic

particles. Just tr y ing to control them risks

making them lose their quantum properties.

Just linking them together took years of work,

w ith the first t wo-qubit computer appearing

in 1998.

This all changed over 20 years ago, when

superconducting circuits were pioneered in

Japan. This involves cooling qubits to -273

degrees Celsius using powerful fridges. Using

this method, Intel has achieved 49 qubits, and

IBM boasts 53. Google’s game-changing

Sycamore processor also has 53 qubits, but the

tech giant’s already built another w ith 72. A start-

up w ith $119.5 million (£93 million) in funding

called Rigetti even says it’s working

on a 128-qubit system.

But it’s harder to cool large objects

than it is smaller ones, especially

when you need them to be colder

than the depths of space. So just as

superconducting qubits have

reached the size that they can

achieve quantum supremac y, they

may be about to outgrow the

refrigerators they rely on.

One alternative is to use ions, any atom w ith

an added electrical charge. These can be trapped

using microchips that emit electric fields.

Each microchip can then be used as a qubit.

Crucially, these can work at room temperature,

so solve the fridge problem. But trapped ions

have only been tested in labs,

and w ill take a long time to build

on the industrial scale that’s

needed. Microsoft, meanwhile, is

experimenting with topological

qubits, which would be less

sensitive to temperature, but

this involves splitting electrons.

You could say this technolog y is in

a quantum state of its ow n: it’s

both making important

breakthroughs and at the same time we’re only

just beginning to understand it.

“Feynman

provided a

blueprint

for how the

technology

could work”

Google’s CEO, Sundar Pichai,

inspects one of the search

giant’s quantum computers

© Google

Professor Hensinger thinks trapped-ion

quantum computers are the future

© University of Sussex