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University of Chicago physicists have experimentally demonstrated, for the first time, that atoms chilled to temperatures near absolute zero may behave
like seemingly unrelated natural systems of vastly different scales, offering potential insights into links between the atomic realm and deep questions of cosmology.
This ultracold state, called “quantum criticality,” hints at similarities between such diverse phenomena as the gravitational dynamics of
black holes or the exotic conditions that prevailed at the birth of the universe, said Cheng Chin, associate professor in physics at UChicago.
The results could even point to ways of simulating cosmological phenomena of the early universe by studying systems of atoms in states of quantum criticality.
“Quantum criticality is the entry point for us to make connections between our observations and other systems in nature,” said Chin, whose team is the first to
observe quantum criticality in ultracold atoms in optical lattices — a regular array of cells formed by multiple laser beams that capture and localize individual
atoms. Chin, UChicago graduate student Xibo Zhang and two co-authors published their observations online Feb. 16 in Science Express and in the March 2 issue of Science.
Quantum criticality emerges only in the vicinity of a quantum phase transition.
In the physics of everyday life, rather mundane phase transitions occur when, for example, water freezes into ice in response to a drop in temperature.
The far more elusive and exotic quantum phase transitions occur only at ultracold temperatures under the influence of magnetism, pressure or other factors.
“This is a very important step in having a complete test of the theory of quantum criticality in a system that you can characterize and measure extremely
well,” said Harvard University physics professor Subir Sachdev about the UChicago study.
Physicists have extensively investigated quantum criticality in crystals, superconductors and magnetic materials, especially as it pertains to
the motions of electrons. “Those efforts are impeded by the fact that we can’t go in and really look at what every electron is doing and all the
various properties at will,” Sachdev said.
Sachdev’s theoretical work has revealed a deep mathematical connection between how subatomic particles behave near a quantum critical point and
the gravitational dynamics of black holes. A few years hence, offshoots of the Chicago experiments could provide a testing ground for such ideas, he said.
Two inspiraling black holes on the path to merger. Credit: NASA
There are two types of critical points, which separate one phase from another. The Chicago paper deals with the simpler of the two types, an
important milestone to tackling the more complex version, Sachdev said. “I imagine that’s going to happen in the next year or two, and that’s
what we’re all looking forward to now,” he said.
Critical experiments
Other teams at UChicago and elsewhere have observed quantum criticality under completely different experimental conditions.
In 2010, for example, a team led by Thomas Rosenbaum, the John T. Wilson Distinguished Service Professor in Physics at UChicago,
observed quantum criticality in a sample of pure chromium when it was subjected to ultrahigh pressures.
Zhang, who will receive his doctorate this month, invested nearly two and a half years of work in the latest findings from
Chin’s laboratory. Co-authoring the study with Zhang and Chin were Chen-Lung Hung, PhD’11, now a postdoctoral scientist at the
California Institute of Technology, and UChicago postdoctoral scientist Shih-Kuang Tung.
In their tabletop experiments, the Chicago scientists use sets of crossed laser beams to trap and cool up to 20,000 cesium atoms
in a horizontal plane contained within an eight-inch cylindrical vacuum chamber. The process transforms the atoms from a hot gas to
a superfluid, an exotic form of matter that exists only at temperatures hundreds of degrees below zero.
“The whole experiment takes six to seven seconds and we can repeat the experiment again and again,” Zhang said.
The experimental apparatus includes a CCD camera sensitive enough to image the distribution of atoms in a state of quantum criticality.
The CCD camera records the intensity of laser light as it enters that vacuum chamber containing thousands of specially configured ultracold atoms.
“What we record on the camera is essentially a shadow cast by the atoms,” Chin explained.
The UChicago scientists first looked for signs of quantum criticality in experiments performed at ultracold temperatures from 30 to 12
nano-Kelvin, but failed to see convincing evidence. Last year they were able to push the temperatures down to 5.8 nano-Kelvin, just billionths of
a degree above absolute zero (minus 459 degrees Fahrenehit). “It turns out that you need to go below 10 nano-Kelvin in order to see this phenomenon in our
system,” Chin said.
Chin’s team has been especially interested in the possibility of using ultracold atoms to simulate the evolution of the early universe.
This ambition stems from the quantum simulation concept that Nobel laureate Richard Feynman proposed in 1981. Feynman maintained that
if scientists understand one quantum system well enough, they might be able to use it to simulate the operations of another system that can be
difficult to study directly.
For some, like Harvard’s Sachdev, quantum criticality in ultracold atoms is worthy of study as a physical system in its own right.
“I want to understand it for its own beautiful quantum properties rather than viewing it as a simulation of something else,” he said.
Abnormal Star Discovered In The 'Forbidden Zone'
A team of astrophysicists from Germany, France and Italy have discovered in the constellation Leo is an old star.
The star's existence raised at once many questions for scientists.
The object is definitely not as its "contemporaries" that appeared immediately after the Big Bang event.
Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the
course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view.
Gigantic Icebergs Floating In Space
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Bright Star In The Constellation Lyra Is Cooler Than The Human Body
The coldest class of stars have temperatures as cool as the human body.
Astronomers hunted these dark orbs, termed Y dwarfs, for more than a decade without success.
When viewed with a visible-light telescope, they are nearly impossible to see.
Thermonuclear Burning In A Neutron Star Detected For The First Time!
It's a very important discovery!
For the first time, an international team of scientists have detected all phases of thermonuclear burning in a
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Alcubierre Warp Drive - A Doomsday Weapon?
Is the Alcubierre warp drive a doomsday weapon or our passport to the Universe?
The Alcubierre warp drive is a theoretical tool that would allow for spacecraft to travel long distances in space rapidly,
by deforming the space-time continuum in a bubble around the spaceship...
Astronomical Mystery - Tremendous Explosion And Appearance Of Odd Rings
Twenty five years ago, on 1987 February 23, the brightest supernova of modern times was observed in the Large Magellanic Cloud.
The collision occurred at speeds near 60 million kilometers per hour and shock-heats the ring material causing it to glow.
Over time, astronomers have watched and waited for the expanding debris from this tremendous stellar explosion to crash into previously expelled material...
Giant Jupiter - Our "Would-Be" Friend With Secrets From The Past
It knocked a giant planet into deep space, swallowed up a smaller rival before it could grow any bigger.
Careful observers saw dark spots rapidly changing places and almost a century ago, a luminous protuberance on the eastern edge of Jupiter,
on the equatorial side of the north equatorial belt was reported.
Stars In The Milky Way Move In Mysterious Ways
Appearently we still have a lot to learn about the stars in the Milky Way.
Something strange has been noticed about the stars in our galaxy.
Rather than moving in circles around the center of the Milky Way, all the stars in our Galaxy are travelling along different paths,
moving away from the Galactic center.
Never Ending Winter In Our Solar System
There's no lack of ice in our solar system.
Frozen water can be found almost everywhere: the poles of Mercury, Earth, the moon and Mars; the rings and icy satellites of the outer planets;
and in comets that come whizzing past.
Winter in our Solar system is not as we know it on our planet.
MessageToEagle.com -
University of Chicago physicists have experimentally demonstrated, for the first time, that atoms chilled to temperatures near absolute zero may behave
like seemingly unrelated natural systems of vastly different scales, offering potential insights into links between the atomic realm and deep questions of cosmology.
A team of astrophysicists from Germany, France and Italy have discovered in the constellation Leo is an old star.
The star's existence raised at once many questions for scientists.
The object is definitely not as its "contemporaries" that appeared immediately after the Big Bang event.
Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the
course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view.
The origin of Earth's water is hotly debated. New discoveries suggest that our planet's seas could once have been giant icebergs floating through space.
The reason why it remains unclear how our oceans were created is because our planet formed at such high temperatures that any original water must have evaporated.
The coldest class of stars have temperatures as cool as the human body.
Astronomers hunted these dark orbs, termed Y dwarfs, for more than a decade without success.
When viewed with a visible-light telescope, they are nearly impossible to see.
It's a very important discovery!
For the first time, an international team of scientists have detected all phases of thermonuclear burning in a
neutron star, located close to the center of the galaxy in the globular cluster Terzan 5.
Is the Alcubierre warp drive a doomsday weapon or our passport to the Universe?
The Alcubierre warp drive is a theoretical tool that would allow for spacecraft to travel long distances in space rapidly,
by deforming the space-time continuum in a bubble around the spaceship...
Twenty five years ago, on 1987 February 23, the brightest supernova of modern times was observed in the Large Magellanic Cloud.
It knocked a giant planet into deep space, swallowed up a smaller rival before it could grow any bigger.
Appearently we still have a lot to learn about the stars in the Milky Way.
Something strange has been noticed about the stars in our galaxy.
Rather than moving in circles around the center of the Milky Way, all the stars in our Galaxy are travelling along different paths,
moving away from the Galactic center.
There's no lack of ice in our solar system.