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Sub-Poissonian Photon Gun by Coherent Diffusive Photonics

Periodic Reporting for period 1 - PhoG (Sub-Poissonian Photon Gun by Coherent Diffusive Photonics)

Reporting period: 2018-10-01 to 2020-03-31

"Sub-Poissonian Photon Gun by Coherent Diffusive Photonics

Project PhoG develops a family of unique devices for generation of quantum states of light, a tailored light with user-selected properties. PhoG devices are based on engineered nonlinear loss in dissipatively-coupled optical waveguide networks, with the ""cheap"" attenuated coherent states as input. The nonlinear loss acts over much faster timescales than conventional (linear) loss, and so the system is robust to realistic physical limitations. In different regimes, PhoG acts either as a deterministic source of highly sub-Poissonian light, or as a source of entangled photons in different state configurations. Such wide performance range is enabled by a unique physical mechanism behind PhoG and by unique capabilities of the ultrafast laser inscription techniques. The strength of this approach is the ability to inscribe arbitrary patterns of 3-dimensional waveguide structures to create a desired configuration. The devices are compact, on a glass chip. Modern technologies widely use such integrated platforms which renders PhoG highly compatible with current technological systems.

Such quantum sources PhoGs (Photon Guns) will enhance the performance of many protocols across the Quantum Technologies arena by providing a ready alternative to attenuated quantum coherent states which are normally used because of their convenience. Within the project, we implement these devices to enhance super-resolution imaging and to improve stability of the commercial atomic clock. We will create proof-of-principle demonstrations of these applications. For the characterisation purposes, we have developed a unique detector, that can resolve large photon numbers and is based on the established concept of time-multiplexing, which was pioneered by members of the consortium.

The test board and the algorithms have been developed for the application of PhoG in super-resolution microscopy. Laser light passing through a quantum network of PhoG is transformed into special, entangled states of light. This allows to highly enhance the image quality using spatiotemporal quantum correlations. Apart from the purely quantum realm, our coherent devices can have classical applications, be used in quantum-inspired technologies, perform better than standard classical devices. They will enrich integrated quantum photonics with devices in unusual operational regimes and can be generalised to other photonic integrated circuits (PIC) platforms."
Within the PhoG project, we have designed , commenced implementation and in the next phase will apply a family of low-resource, compact and versatile sources of quantum light with user-selected properties and for some configurations also deterministic. The design has been elaborated by theory partners USTAN and IPNASB in close collaboration with HWU (implementation), UPB (characterization) and CSEM (applications).

For the characterisation purposes, we have developed a large photon-number resolving detector functioning up-to-100-bin . It is based on the established concept of time-multiplexing, which was pioneered by members of the consortium (UPB partner).
The test board and the algorithms have been developed for the application of PhoG in super-resolution microscopy on the technological platform of the CSEM partner with the theory support mainly by IPNASB. Laser light passing through quantum network of PhoG is transformed into special, entangled states of light. This allows to highly enhance the image quality using spatiotemporal quantum correlations. The SuperEllen detector, developed by a team form Fondazione Bruno Kessler (FBK) in the past EU projects SUPERTWIN (http://www.supertwin.eu/ ) is used for signal recording.
In today’s quantum optics laboratories, we primarily find two families of quantum states: (1) Discrete variable states characterised by their photon number distributions. In most experiments, these states comprise less than three photons. (2) Continuous variable states. Prominent examples of continuous variable states are single- and two-mode squeezed states. After adding the local oscillator required for detection, these states contains 1012 to 1015 photons. In PhoG, we create quantum states that live in between, with intensities ranging from the few-photon level up to powers in the micro- to milliwatt regime and with the unique feature of photon-number statistics with a reduced variance. Hence they are characterised by typical discrete variable quantities, whereas their brightness is clearly in the regime of continuous variables. Such states are challenging to detect. To tackle this obstacle, we have developed different detection schemes. In particular, the partner UPB has constructed and tested a large photon-number resolving detector. It is based on the established concept of time-multiplexing, which was pioneered by this member of the consortium. Thus, the PhoG project will complement the quantum sources and detectors developed and/or used across the Quantum Flagship, and in general across the Quantum Technologies arena, with the quantum devices operating in a unique performance range.

In terms of societal applications beyond quantum realm, PhoG will contribute to the development of complex, custom designed 3 dimensional waveguide components that can be quickly changed and prototyped. It will advance on a new level use of mid-infrared transmissive, high refractive index non-linear materials. This is in particular important for biological applications, as mid-infrared sources and detectors allow access to the “fingerprint” region where compounds and molecules have distinct spectra allowing them to be identified. Custom light guiding components, spectrographs and lens arrays for the mid-infrared can be developed for minimally invasive portable detectors for precise and rapid clinical diagnosis and identification of diseases. For astronomical applications, integrated high precision, low loss spectrographs for the mid-infrared can be produced, which when used with ground-based telescopes operating with adaptive optics have the potential to identify and characterise Earth-like planets with the possibility to search for those capable of supporting life. Though not explicitly within the scope of the PhoG project, these PhoG-related advances of techniques and expertise of partners contributes to further progress in all these applications.
Generation of strongly sub-Poissonian light from a coherent input using a waveguide network with eng