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sciencemag.org SCIENCE

ILLUSTRATION: ANDY GILMORE

Developers of quantum computers face their true challenge:

taming the noise that plagues the intertwined quantum bits

NO ROOM FOR ERROR

FEATURES

I

n October 2019, researchers at Google

announced to great fanfare that their

embryonic quantum computer had

solved a problem that would over-

whelm the best supercomputers.

Some said the milestone, known as

quantum supremacy, marked the

dawn of the age of quantum com-

puting (Science, 27 September 2019,

p. 1364). However, Greg Kuperberg, a

mathematician at the University of Cali-

fornia, Davis, who specializes in quantum

computing, wasn’t so impressed. He had

expected Google to aim for a goal that is

less flashy but, he says, far more important.

Whether it’s calculating your taxes or

making Mario jump a canyon, your com-

puter works its magic by manipulating

long strings of bits that can be set to 0 or 1.

In contrast, a quantum computer employs

quantum bits, or qubits, that can be both

0 and 1 at the same time, the equivalent of

you sitting at both ends of your couch at

once. Embodied in ions, photons, or tiny

superconducting circuits, such two-way

By Adrian Cho

130 10 JULY 2020 • VOL 369 ISSUE 6500

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