Description of the project. Efficient Chip-Integrated Photon Counting Detectors

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We propose a new type of photodector based on multiplexed chip-integrated evanescently coupled superconducting films. This approach can achieve single-photon resolution up to hundreds of photons- a hundred-fold improvement over current devices. Our team developed evanescently coupled photon counting detectors in an EPSRC-funded collaboration with the groups of Peter Smith (ORC, Southampton) and Sae Woo Nam (NIST Boulder).The concept is that silica-on-silicon waveguides are fabricated sufficiently close to the chip surface so that thin metal films deposited on the surface absorb the evanescent field of the guided mode. Here, we leverage a unique aspect of this detector design: light that is not absorbed by a detector remains in the guided mode. The evanescent coupling therefore enables an efficient, highly scalable scheme that chains together a series of many detection elements. We will develop devices with two types of elements that provide complementary performance in timing and number resolution: transition edge sensors (TESs) and superconducting nanowire single-photon detectors (SNSPDs). In isolation, these elements are saturated with one (SNSPD) or a few (TES) photons. Effective multiplexing avoids element saturation while detecting many excitations in sum.This project aims to deliver the first multiplexed detector with single-photon resolution extending over a hundred photons. The work will include device modelling, characterisation by quantum detector tomography, and a theoretical study on the limits of multiplexed detectors. The student will also work alongside NQIT photonics researchers to progress application in photonic quantum simulators and an entanglement-based quantum random number generator (QRNG)