Quantum computers get new spin on life

Quantum computers just got a couple steps closer to reality, thanks to researchers from the University of New South Wales (UNSW) in Australia.

Qubits are the quantum bits within the systems that record the 1's and 0's needed for processing information. For a quantum computer to work and be practical, you need to be able to construct a way of creating and affecting these qubits, as well as producing them in a workable fashion. The spin of a single electron on an atom of phosphorus attached to a silicon chip is one of the more promising avenues of creating a practical quantum computer.

To use these materials, the atoms of phosphorus and their attendant electrons must be as close as 0.0000001 inch apart from one another. This closeness presents difficulties in both the construction and operation of such systems. One of the problems is that if you change the spin of a single electron, the spin of its neighbors also change.

"[I]f each electron is hosted by a different number of phosphorus atoms, then the qubits will respond to different electromagnetic fields - and each qubit can be distinguished from the others around it," Holger Büch, lead author of the new study, said.

When physicists speak of the spin of a particle, they are not referring to a physical spinning of the object. The term is related to effects the particle has, similar to a magnetic field. Such spin can either be "up" or "down," which represent the ones and zeros in the processor. They can also be in both states at once.

Michelle Simmons and her research team at UNSW have found a way to read these qubits of information, even when they are located a tiny distance apart. Instead of using single atoms of phosphorus, they used several such atoms, which allow the magnetic fields to create a qubit which can be created and read without interference from nearby electrons.

They have also devised a way to construct the devices more easily, with help from researchers at Sandia National Laboratory in New Mexico.

To create the new device, Simmons and her team took a silicon wafer covered in hydrogen atoms, then carved a pattern on the surface in a high vacuum. The object was then sprayed with phosphine gas and heated, sealing the atoms of phosphorus to the surface.

"This first demonstration that we can maintain long spin lifetimes of electrons on multi-donor systems is very powerful. It offers a new method for addressing individual qubits, putting us one step closer to realizing a practical, large-scale quantum computer," Simmons said.

Quantum computers should be able to perform significantly faster than today's technology. Because the spin of electrons can be either up, down, or a combonation of those states, quantum computers can offer a significant ability to perform parallel processing.

Research into the technology was published in the journal Nature Communications.

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