Researchers at Princeton
University have begun crystallizing light as part of an effort to answer
fundamental questions about the physics of matter.
The researchers are not shining light through crystal – they are transforming light
intocrystal.
As part of an effort to develop exotic materials such as
room-temperature superconductors, the researchers have locked together
photons, the basic element of light, so that they become fixed in place.
“It’s something that we have never seen before,” said
Andrew Houck, an associate professor of electrical engineering and one of the researchers. “This is a new behavior for light.”
The results raise intriguing possibilities for a variety of future
materials. But the researchers also intend to use the method to address
questions about the fundamental study of matter, a field called
condensed matter physics.
“We are interested in exploring – and ultimately controlling and directing – the flow of energy at the atomic level,” said
Hakan Türeci,
an assistant professor of electrical engineering and a member of the
research team. “The goal is to better understand current materials and
processes and to evaluate materials that we cannot yet create.”
The team’s findings,
reportedonline
on Sept. 8 in the journal Physical Review X, are part of an effort to
answer fundamental questions about atomic behavior by creating a device
that can simulate the behavior of subatomic particles. Such a tool could
be an invaluable
method for answering questions about atoms and molecules that are not answerable even with today’s most advanced computers.
In part, that is because current computers operate under the rules of
classical mechanics, which is a system that describes the everyday
world containing things like bowling balls and planets. But the world of
atoms and photons obeys the rules of quantum mechanics, which include a
number of strange and very counterintuitive features. One of these odd
properties is called “entanglement” in which multiple particles become
linked and can affect each other over long distances.
The difference between the quantum and classical rules limits a
standard computer’s ability to efficiently study quantum systems.
Because the computer operates under classical rules, it simply cannot
grapple with many of the features of the quantum world. Scientists have
long believed that a computer based on the rules of quantum mechanics
could allow them to crack problems that are currently unsolvable. Such a
computer could answer the questions about materials that the Princeton
team is pursuing, but building a general-purpose quantum computer has
proven to be incredibly difficult and requires further research.
Another approach, which the Princeton team is taking, is to build a
system that directly simulates the desired quantum behavior. Although
each machine is limited to a single task, it would allow researchers to
answer important questions without having to solve some of the more
difficult problems involved in creating a general-purpose quantum
computer. In a way, it is like answering questions about airplane design
by studying a model airplane in a wind tunnel – solving problems with a
physical simulation rather than a digital computer.
In addition to answering questions about currently existing material,
the device also could allow physicists to explore fundamental questions
about the behavior of matter by mimicking materials that only exist in
physicists’ imaginations.
To build their machine, the researchers created a structure made of
superconducting materials that contains 100 billion atoms engineered to
act as a single “artificial atom.” They placed the artificial atom close
to a superconducting wire containing photons.
By the rules of quantum mechanics, the photons on the wire inherit
some of the properties of the artificial atom – in a sense linking them.
Normally photons do not interact with each other, but in this system
the researchers are able to create new behavior in which the photons
begin to interact in some ways like particles.
“We have used this blending together of the photons and the atom to
artificially devise strong interactions among the photons,” said Darius
Sadri, a postdoctoral researcher and one of the authors. “These
interactions then lead to completely new collective behavior for light –
akin to the phases of matter, like liquids and crystals, studied in
condensed matter physics.”
Türeci said that scientists have explored the nature of light for
centuries; discovering that sometimes light behaves like a wave and
other times like a particle. In the lab at Princeton, the researchers
have engineered a new behavior.
“Here we set up a situation where light effectively behaves like a
particle in the sense that two photons can interact very strongly,” he
said. “In one mode of operation, light sloshes back and forth like a
liquid; in the other, it freezes.”
The current device is relatively small, with only two sites where an
artificial atom is paired with a superconducting wire. But the
researchers say that by expanding the device and the number of
interactions, they can increase their ability to simulate more complex
systems – growing from the simulation of a single molecule to that of an
entire material. In the future, the team plans to build devices with
hundreds of sites with which they hope to observe exotic phases of light
such as superfluids and insulators.
“There is a lot of new physics that can be done even with these small
systems,” said James Raftery, a graduate student in electrical
engineering and one of the authors. “But as we scale up, we will be able
to tackle some really interesting questions.”
Besides Houck, Türeci, Sadri and Raftery, the research team included
Sebastian Schmidt, a senior researcher at the Institute for Theoretical
Physics at ETH Zurich, Switzerland. Support for the project was provided
by: the Eric and Wendy Schmidt Transformative Technology Fund; the
National Science Foundation; the David and Lucile Packard Foundation;
the U.S. Army Research Office; and the Swiss National Science
Foundation.
Read more at http://scienceblog.com/74321/solid-light-compute-previously-unsolvable-problems/#I0rPzFLyip23rCWR.99
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