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Project Topic
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High-dimensional (HD) photonic quantum information (QI) promises considerable advantages compared to the two-dimensional qubit paradigm, from increased quantum communi¬cation rates to increased robustness for entanglement distribution. This project aims to unlock the potential of HD QI by encoding information in the spectral-temporal (ST) degrees of freedom of light. We will develop matched experimental tools and theoretical archi¬tectures for manipulating and characterizing such states, and we will demonstrate their use in applications. Every light beam has a large capacity for information coding in its ST degrees of freedom, which, through broadband optical fiber communications, underpins the massive capacity of the internet. Quantum light beams inherit this capacity, which has been as-of-yet underexplored and underutilized. ST control of quantum states of light enables multiplexing of QI in a single spatial mode, ideally suited for guided-wave communications and integrated devices. QI encoding in HD states, going well beyond two-dimensional encoding, has been recognized as a promising way towards enhanced QI processing, communication, and sensing. Even with an increasing number of theoretical proposals, there are, however, few experimental demonstrations of this capability. What is needed is a unified theoretical approach to HD quantum states that is relevant to real experimental devices, accounting for real-world imperfections in order to unlock the full potential of ST-encoded HD QI processing. This project will deliver such a joint effort to bridge this gap. We will carry out connected theoretical and experimental research to achieve secure communication in bipartite and multipartite scenarios, enhance the performance of quantum networks, and develop efficient methods for dimension witnesses, entanglement certification, estimation of properties of quantum states and channels, and quantum metrology. Moreover, we will introduce and develop the new concept of HD quantum temporal imaging. Experimental implementation will be based on novel HD encodings in time and frequency based on ultrafast quantum optical approaches in nonlinear waveguide and electro-optic devices. Encodings using broadband field-orthogonal overlapping pulse modes as well as distinct, non-overlapping time and frequency bins will be explored and brought together to form an effective hybrid-encoded network. Key to experimentally accessing the HD potential of the ST encoding will be the noiseless manipulation of time scales using the concepts of quantum temporal imaging. Combined experimental and theoretical efforts will yield a unified platform for HD, integrated optical QI processing, communication, and sensing. Our project has direct relevance to three Target Outcomes addressed in the QuantERA call, namely, quantum communications (QC), quantum information sciences (QIS), and quantum metrology, sensing and imaging (QMSI). For QC target outcome, we are aiming to develop new communication protocols based on high-dimensional encodings of pulse modes and time-frequency bins with functionality enhanced by quantum effects. We shall also investigate quantum networks in higher dimension. With respect to QIS target outcome, we shall investigate several concepts in quantum information for higher-dimensional quantum systems, ranging from entanglement detection and Bell-inequality violation to efficient estimation of quantum states and properties of quantum channels. Regarding the QMSI target outcome, we intend to develop a new kind of quantum imaging – quantum temporal imaging – directly inspired by its spatial counterpart. We shall also develop the detection schemes that are optimised with respect to various components of the QC network.
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