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448 29 APRIL 2022 • VOL 376 ISSUE 6592 science.org SCIENCE

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K

ent Irwin has a vision: He aims to

build a glorified radio that will re-

veal the nature of dark matter, the

invisible stuff that makes up 85%

of all matter. For decades, physi-

cists have struggled to figure out

what the stuff is, stalking one hy-

pothetical particle after another,

only to come up empty. However,

if dark matter consists of certain nearly

massless particles, then in the right set-

ting it might generate faint, unquenchable

radio waves. Irwin, a quantum physicist at

Stanford University, plans to tune in to that

signal in an experiment called Dark Matter

Radio (DM Radio).

No ordinary radio will do. To make the

experiment practical, Irwin’s team plans to

transform it into a quantum sensor—one

that exploits the strange rules of quantum

mechanics. Quantum sensors are a hot topic,

having received $1.275 billion in funding

in the 2018 U.S. National Quantum Initia-

tive. Some scientists are employing them as

microscopes and gravimeters. But because

of the devices’ unparalleled sensitivity, Ir-

win says, “dark matter is a killer app for

quantum sensing.”

DM Radio is just one of many new efforts

to use quantum sensors to hunt the stuff.

Some approaches detect the granularity of

the subatomic realm, in which matter and

energy come in tiny packets called quanta.

Others exploit the trade-offs implicit in the

famous Heisenberg uncertainty principle.

Still others borrow technologies being de-

veloped for quantum computing. Physicists

don’t agree on the definition of a quantum

sensor, and none of the concepts is entirely

new. “I would argue that quantum sens-

ing has been happening in one form or an-

other for a century,” says Peter Abbamonte,

a condensed matter physicist and leader of

the Center on Quantum Sensing and Quan-

tum Materials at the University of Illinois,

Urbana-Champaign (UIUC).

Still, Yonatan Kahn, a theoretical physi-

cist at UIUC, says quantum sensors open the

way to testing new ideas for what dark mat-

ter might be. “You shouldn’t just go blindly

looking” for dark matter, Kahn says. “But

even if your model is made of bubblegum

By Adrian Cho

FEATURES

A QUANTUM SENSE FOR

DARK MAT TER

By harnessing the strange rules of the subatomic realm,

quantum sensors could solve one of the universe’s biggest mysteries