Integrated optics – from single photon sources to complex photonic circuits

Philip P. J. Schrinner, Carsten Schuck

J. P. Sprengers, Alessandro Gaggero, Dondu Sahin +10 more

The monolithic integration of single-photon sources, passive optical circuits, and single-photon detectors enables complex and scalable quantum photonic integrated circuits, for application in linear-optics quantum computing and quantum communications. Here, we demonstrate a key component of such a circuit, a waveguide single-photon detector. Our detectors, based on superconducting nanowires on GaAs ridge waveguides, provide high efficiency (∼20%) at telecom wavelengths, high timing accuracy (∼60 ps), and response time in the ns range and are fully compatible with the integration of single-photon sources, passive networks, and modulators.

Jonathan C. F. Matthews, Alberto Politi, André Stefanov +14 more

Wolfram H. P. Pernice, Simone Ferrari

Quantum photonic circuits based on nanophotonic components hold promise for overcoming scalability limitations in optical quantum systems. Functional systems will require the co-integration of single photon sources, detectors and tunable photonic components. Waveguide integrated single photon detectors based on superconducting nanowires (SNSPDs) have been shown to fulfill the demanding requirements for on-chip quantum photonics. Because they provide very wide optical detection bandwidth, their use with optically pumped single photon sources poses severe challenges for on-chip filtering. We overcome these challenges by co-integrating electrically driven single photon sources with superconducting detectors. Single photon sources with nanoscale footprint are realized by depositing electrically contacted carbon nanotubes (CNTs) across nanophotonic waveguides. CNTs under electrical current bias are shown to emit non-classical light which is coupled efficiently into the underlying photonic framework. The CNTs are shown to provide high count rates in the MHz range. The statistical characterization of the CNT light source crucially relies on the high timing resolution of the SNSPDs which allows for measuring photon statistics for emitters with sub-100ps lifetime. The combination of top-down nanofabrication with deposition by electrophoresis provides a waferscale approach for realizing non-classical circuits on chip. Such hybrid quantum photonic devices therefore hold promise for realizing complex integrated devices without additional optical input ports.

Jonathan C. F. Matthews, Alberto Politi, Anthony Laing +12 more

Łukasz Dusanowski, Dominik Köck, Christian Schneider +1 more

Scalable quantum photonic technologies require the low-loss integration of many identical single-photon sources with photonic circuitry on a chip. Relatively complex quantum photonic circuits have already been demonstrated; however, sources used so far relied on parametric down-conversion which has a probabilistic nature that intrinsically limits its efficiency and scalability. Quantum emitter-based single-photon sources are free of this limitation, but frequency matching of multiple emitters within a single circuit remains challenging. In this work, we demonstrate a key component in this regard in the form of a fully monolithic GaAs circuit combining two frequency-matched quantum dot single-photon sources interconnected with a low-loss on-chip beamsplitter connected via single-mode ridge waveguides. This device enabled us to perform a two-photon interference experiment on-chip with a visibility reaching 66%. Our device could be further scaled up, providing a clear path to increasing the complexity of quantum circuits toward fully scalable integrated quantum technologies.