Cavendish Laboratory generates photons for quantum internet

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The University of Cambridge's Cavendish Laboratory has found a way to generate, from solid-state devices, single photons with tailored properties that are identical in quality to lasers that could realise the quantum internet.

In future, single photons will be flying qubits as part of a quantum computing network, a quantum internet. A qubit is a quantum bit of information and is used in quantum computing.  Qubits can come from quantum dots, which are semiconductor nanocrystals embedded in a microchip that are controlled electro-optically. But, the quality of qubit photons generated from these nanocrystals  has been low due to decoherence mechanisms within the materials. A coherent qubit is needed to identify it for computational purposes.

‘Our research has added the concepts of coherent photon shaping and generation to the toolbox of solid-state quantum photonics,’ said Dr Mete Atature. He led the research at the Cavendish Laboratory. ‘We are now achieving a high-rate of single photons which are identical in quality to lasers with the further advantage of coherently programmable waveform.’

To achieve this Atature’s team built a semiconductor Schottky diode device, containing individually addressable quantum dots, for their photon source.  Single photons were generated from the Schottky diode device using resonance fluorescence. The researchers were able to quantify how similar these photons are to lasers in terms of coherence and waveform, it turned out they were identical.

Atature said: ‘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. 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.’