Optical realisation of a quantum computer, secure quantum communications and imaging requires fast and reliable generation of single photons and their quantum superpositions. Future quantum optical sources should be small as they will need to be integrated into future photonics devices so that they fit ‘on-chip’.
When an intense light impinges onto nonlinear material, high energy photons can split into two. This interaction divides their energy, leaving a pair of lower energy photons which are entangled. The first demonstration of a reconfigurable nanoscale light source of entangled two-photon states was realised by the multinational team involving the Photonics & Nanotechnology Group at the Physics Department at King’s College London (King’s).
Nano-antennas are nanometric material structures that strongly interact with light. Optical nano-antennas have already shown a great ability to manipulate photons efficiently, but their potential for production of multi-photon quantum states remained unexplored.
In the framework of a multinational collaboration involving researchers in the UK, Australia, France, Italy and China, Dr Giuseppe Marino, a PhD student from the Photonics & Nanotechnology Group at King’s and current postdoctoral fellow at Université de Paris, has experimentally demonstrated, the nanoscale generation of two-photon quantum states enhanced by the nanoscale semiconductor antenna. It is also easy to achieve the desired spectral response by changing the nano-antenna shape and geometry.
When excited by a laser, the nano-antenna generates pairs of photons at a much higher rate than usual methods. The research ‘Spontaneous photon-pair generation from a dielectric nanoantenna is published in Optica.
These experiments now pave the way to the development of nanoscale structures to generate multi-photon quantum states. Future applications include secure telecommunications and quantum imaging.
“Scalable and integratable nanoscale quantum optical sources are a must if the optical quantum technologies will grow from the lab to real-world applications,” says Professor Zayats, a co-author of the paper, “these results show that indeed such miniaturised optical sources can be engineered not only without compromising the performance but actually with better performance than their traditional bulky counterparts”.
Link to the paper: (doi.org/10.1364/OPTICA.6.001416)