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An international team that includes a Dartmouth physicist has reported
findings that could advance the emerging field of quantum information
processing. The team's findings, reported July 26 in the online version of the
magazine
Science, shed light on how to detect and manipulate the direction of
electron spins, one potential medium for recording data in a quantum
computer.
Yeong-Ah Soh (Photo by Joseph Mehling '69)
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Titled "Mesoscopic Phase Coherence in a Quantum Spin Fluid," the paper "is a
collaboration between groups that have worked together productively over a long
period of time," says Yeong-Ah Soh,
associate professor of physics and astronomy. "The research was successful due
to a combination of factors—namely a good idea, high-quality samples, intensive
measurements at state-of-the-art international facilities supported by in-house
measurements, and, ultimately, good physical insights."
First proposed in the 1970s, quantum computing employs certain quantum
physical properties of atoms or nuclei as the "quantum bits," or "qubits," of
the computer's processor and memory. Unlike today's computer bits, which exist
as either 0s or 1s, qubits have an infinite choice of values, meaning they can
potentially perform multiple operations simultaneously and solve problems
beyond the scope of today's computers.
Quantum physical properties that have been explored for use as qubits
include various properties of photons and ions; the size or energy state of an
electron's orbit around an atom; and the direction of electron spins, the
approach studied by Soh and her colleagues.
The team used imaging technology to analyze samples of a ceramic composed of
chains of nickel-centered oxygen octahedra. This material is known as a "spin
liquid"-one in which the electron spins (analogous to tiny compasses) point in
random directions, with no particular order, even at very low temperatures.
The team found that, contrary to intuition, the electron spins could achieve
"quantum order" even in the spin liquid, and could do so at lengths of up to 20
nanometers, or billionths of a meter. While not much to the naked eye, this
distance is significant in quantum information processing. The team also
studied how they could limit or eliminate the quantum order by heating the
ceramic or introducing chemical impurities.
The work was funded by the Office of Basic Energy Sciences within the U.S.
Department of Energy's Office of Science, the National Science Foundation, a
Wolfson-Royal Society Research Merit Award (U.K.), and by the Basic
Technologies program of the U.K. Research Councils.
By REBECCA BAILEY
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