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Research Activities

The overarching aims of the QCUMbER project are to develop the experimental and theoretical tools required to address the quantum structure of the time-frequency degrees of freedom of ultrashort light pulses and to demonstrate their utility for new types of quantum technologies. The basis for this research direction is the recognition of the vast information capacity enabled by the quantum properties of spectral-temporal multimode states of light and their compatibility with integration and guided-wave distribution over optical fibres. We build upon the well-developed techniques of ultrafast optics, such as frequency combs, pulse shaping and metrology, to realize a long-term vision of massively entangled, controllable quantum states of ultrabroadband light pulses that open new vistas for fundamental science and engineering, in precision spectroscopy, clock synchronization, communications networks and ultimately computing.

To achieve the major goals of QCUMbER, five core research work packages (WPs) guide the project.

WP1: Sources – The ability to reliably generate quantum states of light with well-defined spectral-temporal mode structure is a central resource for this project and the associated photonic quantum technologies we will implement. Here we are developing trains of ultrafast pulses in quantum states optimized for specific applications pursued in WP5. Thus we are working towards different source characteristics, building on expertise from the consortium.

WP2: Coherent manipulation – Control and manipulation of the pulse-mode structure of light in the classical domain often works on principles of amplitude filtering and gain, which do not preserve the fragile quantum features of non-classical states. For example, using a spectral filter to generate narrow bandwidth pulses from initially broader pulses works well with classical lasers, since photon statistics of laser light are robust to loss. However, generating a single-photon pulse with a narrowed spectrum from an initially broader single photon by spectral filtering does not work; it introduces vacuum and leads to a mixed output state. This example highlights the key characteristics required to manipulate the spectral-temporal mode structure of quantum states – lossless unitary transformations of the field. Here we are developing various approaches to coherently control the pulse-mode structure of light that preserve its quantum nature.

WP3: Detection – Harnessing potential advances offered by quantum correlations across multiple time-frequency modes of light requires a new generation of quantum detectors capable of detecting this multiplicity of modes. Here we focus on development of detection techniques to address the increased dimensionality of the optical time-frequency modes. The work is closely tied with progress in the sources, manipulation, theory and applications WPs to ensure that detector bandwidth and resolution are well matched to application requirements.

WP4: Underpinning theory – Central to understanding and quantifying multimode quantum features of the states, coherent manipulation methods and detectors developed during the project is the underlying theoretical description. Here we are developing the foundational theory to describe such complex ultrashort multimode, multi-excitation systems.

WP5: Applications – To demonstrate the potential advances enabled by this project, we are harnessing the experimental and theoretical developments made during the project to realize applications in three areas of quantum technologies: quantum computation, quantum communication, and quantum-enhanced sensing.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 665148.