The team of researchers led by Prof. Mark Thompson at Bristol’s Centre for Quantum Photonics have added new photon-colour leveraging tools to the quantum photonic engineer’s toolbox. By combining high-performance silicon photonics—the same technology pursued by microelectronics heavyweights for on-chip optical interconnects—and quantum optics, the team was able to integrate the production of spectrally structured and entangled light, and its analysis, within a device measuring less than a millimetre in length.

 Sources of photon-pairs, based on silicon microring resonators, could one day produce large and exotic states of light—the raw materials for quantum applications with photons—on-chip. The spectrally structured photons which they produce, however, have until now been a challenge to control. By using a second microring resonator, acting as a demultiplexer, the Bristol researchers were able to precisely control and analyse the photons’ spectral properties. To test their new device, the team entangled the on-chip photon pairs, and used their entanglement as a hallmark of the device’s excellent performance.

This work was published in Nature Communications, on 6 August 2015.