Electron Spins

An international research team may have unlocked the path to quantum information processing by switching an electron’s intrinsic property of being in an excited state to a relaxed state with the use of a microwave “tuning fork.”

The researchers were able to demonstrate this process by zapping an exotic silicon material with microwaves, which had the effect of changing its electron spins from an excited state to a relaxed state. This method causes electrons to emit some of their energy as photons.

On their own, it's very unlikely that electrons will flip to a relaxed state while also emitting a photon. This light emitting effect is also called the Purcell effect, and it happens naturally about once every 10,000 years.

The silicon sample doped with bismuth atoms used in the experiment.

Thomas Schenkel, a physicist in Berkeley Lab’s Accelerator Technology and Applied Physics Division who designed and developed the exotic silicon material used in the study, said that their experiment successfully demonstrated to accelerate and control the relaxation of electron spins and the emission of a microwave photon.

"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," Schenkel describes.

The team’s findings were published online in the journal Nature.

Quantum Information Processing

Patrice Bertet, a quantum electronics scientist from the French Atomic Energy Commission (CEA), said their results are “highly significant for quantum information processing.”

"Indeed, they are a first step toward the strong coupling of individual electron spins to microwave photons, which could form the basis of a new spin-based quantum computer architecture."

The importance of this new method for quantum computing is that electron spins could be a candidate for so-called "qubits"—the informational basis for a quantum computer, analogous to binary bits in electronic computers. The qubit, relying on the arcane properties of quantum mechanics, will not exist as either a binary one or zero, but will be both at the same time, thereby exponentially boosting the computational power of such a computer. In other words, instead of performing one calculation after another in a sequence, a quantum computer can perform multiple calculations simultaneously, and surpass today's most powerful supercomputers by many orders of magnitude.

So the new research is hopefully a step toward making this dream a reality. The idea is to get the microwave photons to work together with the electron spins to move information in novel ways—to yoke these qubits together, and create a functioning, fully integrated quantum computer.

The researchers’ ultimate goal is to find the link between the fixed point of quantum information and the quantum information that “can be transported,” said John Morton, a professor at the London Center for Nanotechnology.

The research could also help boost the sensitivity of scientific techniques that are used in a wide range of experiments, including dynamic nuclear polarization and nuclear magnetic resonance spectroscopy.

Moving forward, the goal for the team is to learn how to trigger the relaxation of electron states on demand, and to speed up the electron-flipping to less than one millisecond, as opposed to the current one-second rate.

Share This Article