THE SAIF's WORLD

Manipulating electron spin mechanically

Dec 04, 2013 by Anne Ju

A schematic drawing of the device, which includes a transducer that produces gigahertz-frequency standing waves within diamond. Credit: Evan MacQuarrie

Contrary to many textbook illustrations, electrons aren't just balls floating around an atom. In quantum theory, they're more like little tops, exhibiting "spin," and each creating its own tiny magnetic field.

Learning how best to manipulate these spins could open up technological advances in everything from quantum computers to encryption protocols to highly sensitive detectors. Usually, scientists exert control over electron spins by applying magnetic fields. It is the same concept that gives us magnetic resonance imaging: A strong magnetic field influences the spins (in MRI's case, of the nuclei) inherent in billions of hydrogen atoms in the body, enough of which can be converted into medical images.

A collaboration of physicists and engineers has found a new way to control electron spins not with a magnetic field but with a mechanical oscillator – a demonstration of electron spin resonance that's "shaken, not stirred," said lead researcher Gregory Fuchs, assistant professor of applied and engineering physics (AEP).

Fuchs and the research team showed that an oscillator – a transducer moving at extremely high frequency – can drive the transitions of electron spins (a phenomenon called spin resonance), within defects commonly found in the crystal lattice of a diamond. Their results were published online Nov. 27 in the journal Physical Review Letters.

In conventional magnetic resonance, a rotating magnetic field twirls around at the same rate as the electrons "spin" – the magnetic field is "stirring" the spins. Instead, the Cornell researchers used an oscillator to "shake" the diamond lattice to directly flip the spins.

Their experiment involved looking at electrons spins within a naturally occurring defect in the crystal lattice of a diamond, called a nitrogen-vacancy center. Spins found within these defects are a promising platform for studying quantum spin control.

The researchers call their electron spin resonance demonstration “shaken, not stirred." While ordinarily spin resonance is induced by “stirring” a spin with a rotating magnetic field, in this work it results from “shaking” a diamond crystal.

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