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Memory-enabled Optical Quantum Communications and Information Networks

Final Report Summary - MOQUACINO (Memory-enabled Optical Quantum Communications and Information Networks)

The probabilistic nature of quantum operations (such as generation, manipulation and measurement of quantum resources like entanglement) limit the scale of current state-of-the-art quantum networks. This ERC advanced grant, MOQUACINO, aims to address this scaling catastrophe with ultrafast quantum optical memories – devices that can store and then efficiently recall quantum states on demand and in a faithful manner – allowing for fast synchronisation of probabilistic quantum operations, enabling scale. MOQUACINO focused on improving one exciting memory candidate, the Raman quantum memory, to enable next generation experiments in quantum networks. We have successfully reduced the unconditional noise-floor in Raman-type memories to be quantum-ready via three approaches: (i) a cavity enhanced scheme; (ii) a build-in noise suppression protocol; (iii) a ladder scheme that is inherently free of noise. The final approach enabled the storage and recall of heralded single photons without modification of the quantum properties of the photon – a world’s first. These results uniquely position the Raman quantum memory as the key technology to empower large quantum photonic networks via temporal multiplexing

The main platform for our quantum memories is warm caesium vapours; we explored the use of ensembles of defects in diamonds (e.g. nitrogen vacancy, silicon vacancy) as a pathway to future miniaturised quantum memories, showcasing Raman interactions in sub-micron sized SiV ensembles. Further to this, we achieved the world’s first experimental demonstration of quantum effects in the operation of microscopic heat engines based on ensembles of ambient temperature NV centres in diamonds.

We have explored new and novel types of photonic networks for metrology, computing, simulation, and as a platform for exploring foundational physics. One highlight has been the first thermodynamic quantum information experiment using photonics: a demonstration of a photonic Maxwell demon. We also explored and characterised three- and four-photon interference, demonstrating multiparticle interference of four photons prepared in pairwise orthogonal states. As a final highlight, we demonstrated an optical simulator for molecular vibronic spectra, demonstrating that it was possible to ascertain estimates of Franck-Condon factors using Gaussian Boson-sampling.

Our continued multifaceted research effort into all aspects of quantum photonic technologies overs a promising route towards large-scale quantum networks. We will continue to develop the necessary quantum light sources, quantum memories, integrated photonic circuits, superconducting detectors and innovative protocols that will underpin the next generation of photonic network-based quantum information technologies.