Researchers Discover Near-Ideal Photon Sources in Silicon Quantum Photonics

At its Build 2020 virtual conference this week Microsoft unveiled one of the world’s top-five publicly disclosed supercomputers, part of the tech giant’s ambition to enable training of extremely large artificial intelligence models. Researchers are naturally drawn to supercomputers due to the massive computing resources they offer. However, as impressive as these machines may be, they cannot compete with the promise of quantum computers at scale.

Also this week, a team of physicists from the University of Bristol introduced the first integrated photon source that can potentially bring quantum computers up to speed by delivering large-scale quantum photonics. In the paper Near-Ideal Spontaneous Photon Sources in Silicon Quantum Photonics, the team introduces photon sources fabricated in silicon that meet a variety of requirements for scalable quantum photonics: high purity, high heralding efficiency, and high indistinguishability.

Integrated photonics is a robust platform for applications in quantum technologies given its ability to use photonic integrated circuits to generate photons and control photonic quantum states with the photon as a primary carrier of information. Despite the high demand for using integrated photonics on a large scale, the lack of on-chip sources that can generate high-quality single photons has hindered advancements.

Because they rely heavily on multiple arrays of photon sources to achieve combinatorial speed-ups in quantum sampling algorithms, all-photonic quantum computing architectures tend to accumulate errors when low-noise photons sources are scarce, particularly if circuit complexity increases. The researchers note that in general, lossy or inefficient heralding of photons vitiates the scaling of photonic quantum information processing.

The paper proposes a solution — intermodal spontaneous four-wave mixing — to generate high-quality single photons. Inter-modal spontaneous four-wave mixing is performed by propagating the pump, signal and idler waves on different waveguide modes to create the ideal conditions for generating single photons.

Experiment results show improvement in computation complexity compared to the previous state-of-the-art integrated photonic devices.

The research team believes these near-ideal spontaneous photon sources in silicon quantum photonics can have a significant impact on the prospects of quantum information processing in integrated photonics; and that the new approach could compete with classical supercomputers in solving sampling problems and potentially lift the computational complexity level to the regime of quantum computational supremacy.

The paper Near-ideal Spontaneous Photon Sources in Silicon Quantum Photonics is available on Nature Communications.

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Journalist: Fangyu Cai | Editor: Michael Sarazen