Quantum computing could be a step closer to reality, with the development of a new technique for generating single photons from solid-state chips.

Moore's Law states that the number of transistors on a microprocessor doubles every two years, but transistors will eventually reach the physical limits of miniaturisation at atomic levels. If the law is to continue, therefore, the microchip industry will need to start investigating quantum mechanics.

One option is to develop a distributed quantum network, which distributes information using single photons. These photons can carry information quickly and reliably across long distances, and can also take part in quantum logic operations, as long as all the photons taking part are identical.

Until now the quality of photons generated from solid-state quantum bits of information (qubits) has been fairly low, due to decoherence mechanisms within the materials. However, researchers from the Cavendish Laboratory at Cambridge University have found a way to avoid photon decoherence altogether.

Using a semiconductor Schottky diode device containing individually addressable quantum dots as their photon source, and operating the source under weak excitation, the team was able to generate single photons with tailored properties that are identical in quality to lasers (that's pretty good).

“Our results in particular suggest that multiple distant qubits in a distributed quantum network can share a highly coherent and programmable photonic interconnect that is liberated from the detrimental properties of the chips,” said Dr Mete Atature from the Department of Physics, who led the research.

“Consequently, the ability to generate quantum entanglement and perform quantum teleportation between distant quantum-dot spin qubits with very high fidelity is now only a matter of time.”

There are already protocols proposed for quantum computing and communication which rely on this photon generation scheme, and this work can be extended to other single photon sources as well, such as single molecules, colour centres in diamond and nanowires.

The research was published in the journal Nature Communications last week.

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