Near-optimal chip-based photon source for quantum computing

Researchers from the University of Bristol have developed a new CMOS-compatible silicon photonics photon source that satisfies all the requirements necessary for large-scale photonic quantum computers. The research represents a significant step toward mass-manufacturable ideal single photon sources.

The mature CMOS fabrication processes used to make today’s computer chips could greatly lower the cost of large-scale quantum computers.

As the name implies, single-photon sources emit light as single photons. They are a key component of optical quantum computers, which use the photons to carry data in the form of qubits. Single-photon sources used in quantum computing have very exacting requirements. They must be highly indistinguishable and pure, either near-deterministic or highly efficient, and suitable for mass-manufacturing.

The team designed a new single-photon source based on inter-modal spontaneous four-wave mixing in a multi-mode silicon waveguide.

The inter-modal approach to on-chip photon sources, where an interplay between multiple optical pump fields is used to generate photons, enables novel degrees of freedom to control the photon emission. By tailoring the geometry of a low-loss multi-mode waveguide and the on-chip temporal delay between the pump fields, the research team showed that the properties of the spontaneous photon emission could be engineered to achieve near-ideal photons.

The researchers also performed on-chip photon interference, which is essential for quantum computations. These experiments produced a raw-data visibility of 96%, the highest reported so far in integrated photonics. This achievement enables on-chip quantum operations between photons at an unprecedented level of precision, opening the possibility to scale-up low-noise photon processing in near-term quantum photonic devices.

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