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NASA uses laser cooling to create 'coldest spot in the Universe'

NASA has launched an instrument that will create what could be the coldest spot in the universe, to allow scientists to study quantum phenomena more effectively, and in turn enable more effective quantum devices such as interferometers and computers.

The Cold Atom Lab could help answer some big questions in modern physics. Credits: NASA/iGoal Animation

The Cold Atom Laboratory (CAL), which is about the size of a small refrigerator, uses laser cooling to produce a temperature 10 billion times colder than the vacuum of space. Results of this research could lead to a number of improved technologies, including sensors, quantum computers and atomic clocks used in spacecraft navigation. 

The instrument is on board the Orbital ATK Cygnus spacecraft, along with other research equipment, and will be operated on the International Space Station (ISS) by a multidisciplinary team of scientists.

The quest for ever colder temperatures has been a major theme of physics for more than a century, leading to such breakthroughs as the discovery of superfluidity and superconductivity, and more recently the development of laser cooling techniques. 

CAL will produce clouds of ultra-cooled atoms called Bose-Einstein condensates (BECs). A BEC is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zero. At these temperatures, which are even colder than the average temperature of deep space, the atoms in a BEC demonstrate quantum characteristics at relatively large size scales, allowing researchers to explore this strange domain.

Beyond the great interest in the scientific aspects of these phenomena, these advances have also been at the heart of several important devices, from superconducting quantum interference devices to laser-cooled atomic clocks and atom interferometer-based sensors, such as a gravity gradiometer for global gravity mapping.

The Cold Atom Lab has being integrated into the Cygnus spacecraft in advance of its 21 May launch. Credit: NASA/Cold Atom Lab

Over the past three decades, much advancement has been made in Earth-based laboratories in reducing the temperature of BECs to below the condensate temperature. Inherent to these experiments is the application of an intense magneto-optical trap to hold the atoms in place to obtain the required cooling, due to the pull of gravity.

The microgravity environment of ISS enables the Cold Atom Laboratory (CAL) laser cooling technology to reach temperatures colder than ever achieved on Earth, and to therefore analyse atom wave functions never observed before. Observation times of more than 10 seconds and temperatures below 100 pK will be achievable in space. 

CAL research findings will facilitate the development of future ultra-cold atom-based quantum sensors for gravitational and magnetic fields, rotations and tests of the equivalence principle.

The CAL instrument utilises commercial off-the-shelf hardware and software, which enabled its rapid development. CAL has quad lock configuration, with electronics components on one side, which are cooled with liquid heat exchangers to maintain a safe operational temperature.

On the other side is the science module and laser assembly, featuring fibre-optic coupled lasers to simplify optic-mechanical design. Forced convection with fans is used to cool the lasers and science module. 

The science module is encased in a magnetic shield to attenuate the magnetic field of the Earth, which varies over the course of the orbit. 

The CAL facility is designed for use by multiple scientific investigators and to be upgradable/maintainable in orbit. CAL will also be a pathfinder experiment for future quantum sensors based on laser cooled atoms enabling exquisitely precise measurements of a wide variety of phenomenon.

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