New_Scientist_11_2_2019

8 | New Scientist | 2 November 2019

QUANTUM supremacy is far

from the end of the road.

Although Google has edged

in front, there are still plenty

of bends, banks and ditches

that could halt the competitors

in the race to build the first truly

useful quantum computer.

As well as Google, research

groups at IBM, Intel and Microsoft,

and a slew of start-ups, are all

developing quantum computers.

And the competition is heating up.

IBM has said that Google’s claims

of quantum supremacy aren’t as

good as they appear – and there

are still plenty of milestones

left for others to claim.

“One of the problems with

this term supremacy is that it

sounds like we have achieved

the revolution of quantum

technology and everybody is

expecting these machines to fly

in the next five years. But the

next five years are going to see

a lot of slow growth,” says Juani

Bermejo-Vega at the University

of Granada in Spain. “We are

living in the prehistory of

quantum computing.”

Over the next few years, each

group will probably attempt to

outdo each other on tasks that

are particularly hard for classical

computers. They have all backed

different ways of making a

quantum computer from quantum

bits, or qubits, so one method

may eventually outpace the rest.

Google’s progress has been

made using superconducting

qubits: components made of

superconducting wire laid in

an insulator. There was already

quite a lot known about this

approach before Google started

experimenting with it, which

has helped the company’s

researchers get this far.

But superconducting qubits are

large and hard to make smaller. At

50 qubits, the size is manageable,

but quantum computers may

need a thousand or a million

to become really useful.

Intel is working both on

superconducting qubits and spin

qubits for its quantum computer.

Spin qubits work by manipulating

the orientation of electrons using

microwave pulses. These qubits

can be operated at slightly higher

temperatures than the other type

and may be simpler to integrate

with current electronics. This

makes it easier to increase their

number and make them smaller,

says Jim Clarke at Intel.

Microsoft has decided to take

yet another route. It aims to use

topological qubits, which rely on

quasiparticles: packets of energy

that behave like a particle. “The

catch is that it requires making

a new form of matter that’s never

been seen before,” says Scott

Aaronson at the University of

Texas at Austin.

There is some indirect evidence

that quasiparticles can be made,

although nobody has managed to

do it yet. The benefit of topological

qubits is that they can naturally

correct some of the errors that

creep into quantum computers.

“Error correction is an even

bigger hurdle than supremacy,

but it’s the obvious next goal,”

says Aaronson.

That goal may be years away.

John Martinis at Google said in

a press conference last week

that the company’s researchers

will experiment with error-

correction experiments over

the next year or two.

So what next? We can expect

that as superconducting qubits

are further improved, the other

types of qubits will also be made

into processors that can achieve

quantum supremacy.

A decade or two down the

line, we may see quantum

computers that can perform

useful calculations, such as

modelling chemical reactions or

interactions in materials science.

But that won’t mean that most

people will get their own quantum

computer any time soon.

“Quantum computers are going

to be located either in the cloud or

in large supercomputing centres,”

says Clarke. “Most people won’t

use them directly. But well after

I retire, 40 to 50 years from now,

I can’t rule anything out.” ❚

News Quantum computing special report

The competition

Chelsea Whyte

Race for useful quantum

devices has begun

“ It’s possible that with 100

qubits that are very clean,

in a few years we will be

doing very interesting

fundamental research”

Juani Bermejo-Vega,

University of Granada in Spain

IBM is one of a host of

companies working on

quantum computers

2019

October

IBM claims Google

hasn’t yet reached

quantum supremacy

because a powerful

computer would

take 2.5 days not

10,000 years to

accomplish the task

Sycamore managed

2020s

Different types

of quantum

computers, for

example those

made with trapped

ions or spin qubits

(see above), will

achieve quantum

supremacy

2030s

Quantum computers

start to be used in

the same way that

powerful computers

are now, finding

uses in chemistry,

materials science,

drug design and

financial services

2040s

By now, quantum

computers contain

millions of qubits,

which would allow

them to break much

of the encryption

currently used to

secure the internet

2050s

Quantum computing

starts to affect daily

life. Some apps

offload part of

their processing to

quantum computers

in the cloud

mid 2020s

Error-correction

algorithms will

create quantum

computers that are

more stable and can

perform calculations

for longer periods

of time

IBM

...and

now New

Scientist ’s

best guess

on what

happens

next