SIBESQ · Silicon-Chip Based Efficient and Scalable Quantum Processing and Production of Photons

Silicon-Chip Based Efficient and Scalable Quantum Processing and Production of Photons

The unconventional and novel scheme of coherent photon conversion (CPC) promises to break with a single device two main conceptual roadblocks in the implementation of scalable photonic quantum information processing – namely the scalable creation of single and multi-photon states, as well as the implementation of a deterministic photon-photon interaction enabling efficient entangling gates. The conceptual and experimental challenge addressed in this project is to approach sufficiently high effective nonlinearities to unlock the full potential of the coherent photon conversion scheme. The highly promising approach followed in this project is using high-Q Silicon Nitride micro-resonators: Integrated silicon nitride structures offer several distinct advantages over the previous implementation for enhancing the effective nonlinearity: a 10 times higher intrinsic nonlinearity than silica, ultra-strong mode-confinement in sub-um-sized waveguides, and the possibility for high-Q micro-cavities which dramatically enhance the electric fields of single photons and therefore their nonlinear interaction. Moreover, the Silicon Nitride platform utilizes highly mature CMOS-fabrication technology, which offers excellent design flexibility and precise control, and therefore enables the straightforward application in other quantum and classical optics technologies. Since the beginning of the project there have been a number of theoretically, technical and experimental advances to first find the best combination of wavelengths for implementing CPC on a chip-based platform. To design suitable chips that were then fabricated and tested it turned out to be crucial to develop and implement a new methodology to experimentally measure the precise dispersion characteristics of the fabricated devices. A fully automated laser-scanning based characterization setup was build. This surprisingly lead to the discovery of a novel and broadly relevant effect in integrated microresonators: the occurrence of strong polarization mode coupling, which can dramatically change the effective dispersion and thus makes it also crucial aspect to be taken into account for implementing CPC. Moreover based on the ultra-high Q-factors in SiN micro-resonators and as a first step into the direction of implementing the full CPC scheme an ultra-narrow band, quantum-entangled photon pair source was implemented and characterized. This type of source, as a first high-profile demonstration of integrated SiN as a promising platform for nonlinear quantum optics is important for interfacing to narrow-band quantum memories. Using our new methodology (a fully automated laser-scanning based characterization setup) developed in the first period of the project to experimentally measure the precise dispersion characteristics of the fabricated devices, we were then able to finally arrive at devices with the desired phase-matching characteristics. As anticipated after the first period these first devices yielded promising first results. The further anticipated results of this ongoing line of research could bring the vision of efficient and nonlinear optical photon-photon interactions within reach of current technology. By pushing the limits of all-optical (quantum) nonlinearities using the CPC-scheme will have important impacts in other emerging quantum technologies such as secure quantum communication or quantum simulation and may also benefit classical, chip-based signal processing. On an additional line of research, closely connected to the basis of CPC - namely coherent quantum frequency conversion - the fellow significantly contributed to a striking result on experimentally realizing a single photon Ramsey-Interferometer. In this demonstration, a single photon was brought into a quantum super-position of two different energy states (by partial frequency conversion). Then free propagation of this state resulted in a phase and corresponding Ramsey fringe, that was observed with be subjecting the super-position state to a second coherent frequency conversion step. Remarkably, this is also the first cascaded demonstration of single photon coherent frequency conversion.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз