Quantum liquid put in an orderly spin

An international team using the UK’s tools have found a new form of quantum order.

Researchers using Britain's world-leading ISIS pulsed neutron and muon source at the STFC Rutherford Appleton Laboratory have detected a new form of quantum order that could have implications for the design of future materials in a range of fields related to nanofabrication and quantum computing.

Muons are particles that have a mass about one-tenth that of a proton or are about 200 times heavier than an electron.
 
In quantum information processing, data is manipulated using 'qubits' – quantum bits.

Single electrons make excellent qubits, but interactions with other electrons mean that useable quantum properties are rapidly lost.

The new results are important because they demonstrate explicitly that, in a practical material, a large number of electron spins can be coupled together to yield a quantum state covering around 100 atoms and extending over a distance of 30 nanometres (billionths of a metre).

Only a few other examples of such quantum states are known and these lead to fascinating properties such as superconductivity and superfluidity.

"The unique capabilities of neutron scattering have made these latest observations possible," said Dr Christopher Frost, Instrument Scientist for the MAPS spectrometer at ISIS, and a co-author on the study.

"By analysing the images from the instrument, we can establish the perfection of the quantum state," he added.

Secrets of the interior world of atoms

MAPS is a revolutionary instrument for neutron scattering at ISIS.

Using neutron spectroscopy, an intense beam of neutrons is scattered from samples of research material and collected by 100 million detector pixels located over an area of 16 square metres, giving a unique view into the interior world of atoms.

The team also discovered that they could manipulate the quantum state, limiting its phase coherence or making it disappear altogether, by introducing defects into the material either by adding chemical impurities or heating.

"Our goal is to understand the factors that affect the distance over which the quantum phase coherence can be maintained and neutron scattering is probably the most direct tool for studying this," said lead author Guangyong Xu from Brookhaven National Laboratory, USA.

"In quantum computing, this state must be must be maintained over a relatively long time in order to store information in the computer.

"This distance — and how sensitive it is to changes in temperature or chemical impurities in the material — can be essential in determining whether a material will have useful applications," he concluded.

The findings were published online in the journal Science.

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