Experiment with Berkeley lab-developed material shows promise for quantum information processing
In what may provide a potential path to processing information in a quantum computer, researchers have switched an intrinsic property of electrons from an excited state to a relaxed state on demand using a device that served as a microwave “tuning fork.”
The team’s findings could also lead to enhancements in magnetic resonance techniques, which are widely used to explore the structure of materials and biomolecules, and for medical imaging.
The international research team, which included scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), demonstrated how to dramatically increase the coupling of microwaves in a specially designed superconducting cavity to a fundamental electron property called spin–which, like a coin, can be flipped.
By zapping an exotic silicon material developed at Berkeley Lab with the microwaves, they found that they could rapidly change the electron spins from an excited state to a relaxed, ground state by causing the electrons to emit some of their energy in the form of microwave particles known as photons.
Left on their own, the electron spins would be extremely unlikely to flip back to a relaxed state and to also emit a photon – the natural rate for this light-emitting effect, known as the Purcell effect, is about once every 10,000 years. The experiment demonstrated an accelerated, controllable relaxation of electron spins and the release of a microwave photon in about 1 second, said Thomas Schenkel, a physicist in Berkeley Lab’s Accelerator Technology and Applied Physics Division who led the design and development of the silicon-bismuth sample used in the experiment.
“It’s like a juggler who throws the balls up, and the balls come down 1,000 times faster than normal, and they also emit a microwave flash as they drop,” he said. The results were published online Feb. 15 in the journal Nature.