E A tomic physicists tend to tinker away on their own, preferably in dark, hushed labs. When Eric Cornell started as a postdoc with Carl Wieman at JILA, an institute run jointly by the National Insti- tute of Standards and Technology and the University of Colorado in Boulder, in 1990 he did his best to
transform their second-floor lab into a base-
ment. “We had these beautiful windows that
looked out over the mountains,” Cornell says,
“and we bought 3-inch-thick Styrofoam and
cut it into squares and taped it over them.”
The quiet and darkness made it easier to fid-
dle with the homemade lasers they were us-
ing to coax atoms into a new state of matter.
Cornell and Wieman were trying to cool
a puff of rubidium gas to within a few
billionths of a degree of absolute zero—
colder than any place in nature, even
the 2.73 kelvins of space. They hoped to
produce a long-predicted state of matter
called a Bose-Einstein condensate (BEC),
in which the atoms shed their individual
identities and crowd en masse into a single
quantum wave. In 1995, they succeeded—a
triumph that earned them a share of the
2001 Nobel Prize in Physics. “We finally un-
plugged that experiment just 2 years ago,”
Now, Cornell and other physicists are
taking their atomic wisps out of seclusion
and into space. Early next year, NASA will
launch its $70 million Cold Atom Labo-
ratory (CAL) to the International Space
Station (ISS). Once in orbit, the fully au-
tomated rig will create BECs and do other
cold atom experiments, taking advantage
of weightlessness to attain record-low tem-
peratures and break ground for ambitious
studies of quantum mechanics and gravity.
Miniaturization is the key: Experiments
that once required a room full of lasers,
optical elements, and vacuum systems can
now fit in a device the size of an ice chest,
with the atoms trapped on the surface of a
microchip. The effort will stretch the cul-
ture of atomic physicists, forcing them to
share a single remote facility, like users of
a space telescope.
“I’ve certainly been pitching this for
20 years, really from the beginning of BECs,
when doing something like this in space
seemed crazy,” says Robert Thompson, a
physicist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, and
CAL’s project scientist.
THERE IS ONE MAIN REASON to do atomic
physics in space. “It’s all about getting away
from gravity,” says Charles Sackett, a physicist at the University of Virginia in Charlottesville and a CAL experimenter. Here’s
the problem: To make a BEC, physicists use
magnets and lasers to trap and chill atoms
so that their speeds drop from thousands
of meters per second to centimeters per
second—slower than a walk. But to probe a
BEC, they must release it from its trap and
shine laser light on it, creating a shadow
that reveals the atoms’ distribution.
On Earth, gravity pulls at the atoms the
moment they are released, typically giving
physicists just 10 to 20 milliseconds to make
their measurements before the BEC crashes
to the bottom of the vacuum chamber. In
the weightlessness of orbit, a BEC should
hover for up to 10 seconds before lingering
gas in the vacuum chamber warms it up,
Sackett says, allowing time for measure-
ments that can’t be made on Earth.
Working in orbit should also push atoms
to lower temperatures. In making a BEC,
the final step begins with the atoms trapped
in a magnetic field (see graphic, p. 988).
Physicists ramp down the magnetic field
so that the trap becomes weaker and wider,
allowing the gas to expand and cool—just
as a can of spray paint gets cold when the
gas inside decompresses. In orbit, the trap
can get weaker and bigger without losing
the atoms, enabling the gases to attain even
Such weightlessness has been mimicked,
fleetingly, on the ground. Since 2007, a
multi-institutional team working at the
Center of Applied Space Technology and
Satyendra Nath Bose and Albert
Einstein predict that ultracold
atoms can crowd into a single
quantum wave: a BEC.
Invention of laser cooling; atomic
gases cooled to below a millikelvin.
Evaporative cooling demonstrated;
atomic hydrogen cooled to
BECs produced at nanokelvin
temperatures by three
BECs produced on an atom chip.
First microgravity studies of cold
atoms in drop-tower experiments.
First BEC in space on
sounding rocket fight.
NASA’s Cold Atom Laboratory to
launch to International Space Station.
ColdQuanta’s atom chip
is key to cooling clouds
of atoms to record low
temperatures in space.
ULTRACOLD MATTER SPECIAL SECTION
Birth of the cool
It has been nearly a century since Bose-Einstein
condensates (BECs) were first predicted,
and more than 20 years since they were first
made. Now, scientists are taking the clouds
of ultracold atoms into space.