Single atom electron spin qubit building block for scalable quantum computer compatible with silicon computer chips

An Australian team unveils the fundamental building block of a scalable quantum computer that could be embedded in today’s silicon chips.

Kane Quantum Computer Proposal – Phosphorus atoms embedded in silicon would be the ideal way to store and manipulate quantum information.Phosphorus atom could store a single qubit for long periods of time in the way it spins. A magnetic field could easily address this qubit using well-known techniques from nuclear magnetic resonance spectroscopy. That would allow single-qubit manipulations but not two-qubit operations, because nuclear spins do not interact significantly of each other.

For that, he suggested transferring the spin to an electron orbiting the phosphorus atom, which would interact much more easily with an electron orbiting a nearby phosphorus atom. Two-qubit operations would then be possible by manipulating the two electrons with electric fields.

Building a Kane quantum computer has become almost an obsession in Australia, where some 100 researchers have been working on the problem for over a decade.

Breakthroughs Achieved
* Able to implant phosphorus atoms at precise locations in silicon using a scanning tunnelling microscope.
* able to address the nuclear spins of these phosphorus atoms using powerful magnetic fields.
* Now able address the spin of an individual electron orbiting a phosphorus atom and to read out its value.

The end result is a device that can store and manipulate a qubit and has the potential to perform two-qubit logic operations with atoms nearby; in other words the fundamental building block of a scalable quantum computer.

Arxiv – A single-Atom Electron Spin Qubit in Silicon

Quantum Competition

Some stiff competition has emerged in the 15 years since Kane published his original design. In particular, physicists have found a straightforward way to store and process quantum information in nitrogen vacancy defects in diamond.

Then there is D-Wave Systems, which already manufactures a scalable quantum computer working in an entirely different way that it has famously sold to companies such as Lockheed Martin and Google.

The big advantage of the Australian design is its compatibility with the existing silicon-based chip-making industry. In theory, it will be straightforward to incorporate this technology into future chips.

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