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ABN 46 006 591 304Laser Light Cools
Quantum Liquid
Australian researchers have used laser light to cool
a special form of quantum liquid called a
superfluid. Lasers are widely used to cool gases
and solid objects, but they have never before been
applied to cool a quantum liquid.
Superfluids are quantum liquids with a strange
property: once started, the flow of a superfluid
never stops. This unique property is a key feature
of many applications proposed for superfluids.
“The applications of this research range from
improved sensors for navigational systems to the
development of quantum devices and fundamental
exploration of the quantum physics of turbulence,
or the turbulent motion of quantum fluids when
cooled to temperatures close to absolute zero,” said
Dr Glen Harris of the ARC Centre of Excellence for
Engineered Quantum Systems.
In the experiments, which were published in
Nature Physics(http://tinyurl.com/z2j23mr), a
superfluid helium film was formed on a silicon chip.
A bright laser beam was then used to draw energy
out of waves on the surface of the superfluid,
cooling them.
In addition to laser cooling, the research
team showed that extremely precise measurements
of superfluid waves could be obtained by
combining a superfluid with microphotonic lasers.
The project’s Chief Investigator, Prof Warwick
Bowen, said that this research provides a pathway
to replace inertial sensors used in navigation
systems. “Previous experiments have shown that
ultra-precise inertial sensing is possible using
superfluid helium,” he said. “However, these
experiments relied upon bulky architectures
somewhat akin to a plumbing system for water.
“The ability to cool, measure and control
superfluid waves on a silicon chip brings a new
level of scalability and integrability to such
sensors.”Human Sacrifices Maintained
Social Power Structures
A new study has reported that ritual human sacriice played a central role
in helping those at the top of the social hierarchy to maintain power over
those at the bottom. “Religion has traditionally been seen as a key driver
of morality and cooperation, but our study inds religious rituals also had
a more sinister role in the evolution of modern societies,” says lead author
Joseph Watts, a PhD candidate at the University of Auckland’sSchool
of Psychology.
The study, published inNature(http://tinyurl.com/zmf57h9) d
computational methods derived from evolutionary biolo
historical data from 93 Austronesian cultures, 40 of which p
form of ritualistic human killing. Early Austronesian peopl
to have originated in Taiwan and eventually settled almost h
They spread west to Madagascar, east to Rapa Nui (Easte
south to the Paciic Islands and New Zealand.
Methods of ritual human sacriice in these cultures inclu
drowning, strangulation, bludgeoning, burial, being cut to p
beneath a newly-built canoe or being rolled off the roof of
decapitated. Victims were typically of low social status, such a
instigators were usually of high social status, such as priests
The study divided the 93 different cultures into three m
high, moderate or low social stratiication. Cultures with the
of stratiication were most likely to practice human sacriic
out of 27). Of cultures with moderate stratiication, 37%
sacriice (17 out of 46) while the most egalitarian societies w
to practise human sacriice (25%, or ive out of 20).
“By using human sacriice to punish taboo violations, d
underclass and instil fear of social elites, power elites were able to maintain
and build social control,” Watts says.
Prof Russell Gray, a co-author of the study, notes that “human sacri-
ice provided a particularly effective means of social control because it
provided a supernatural justiication for punishment. Rulers, such as priests
and chiefs, were often believed to be descended from gods, and ritual
human sacriice was the ultimate demonstration of their power.”
The team’s use of computational evolutionary methods enabled the
team to reconstruct the sequence of changes in human sacriice and social
status over the course of Paciic history. This allowed them to test whether
sacriice preceded or followed changes in social status.
“What we found was that sacriice was the driving force, making soci-
eties more likely to adopt high social status and less likely to revert to egal-
itarian social structure,” said co-author A/Prof Quentin Atkinson.mf 57 h 9 ),used
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