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Research Interests

Quantum metrology Quantum correlations Quantum biology Quantum verification
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Quantum metrology : Metrology is the science, and art, of estimating a parameter precisely. It is a fundamental aspect of investigative science, as well as multitechnology and commerce. Our interests lie in uncovering the fundamental limits that the laws of quantum mechanics impose on the precision of estimating a parameter. In principle, the limits imposed by quantum mechancis allow more precise estimates than those possible using classical resources. These improvements rely on purely quantum phenomonenon such as quantum entanglement and squeezing, and span both discrete variable (spins, qubits) and continuous variable systems. We invent and analyse new scenarios where quantum resources can be employed to attain quantum-enhanced sensing and imaging applications.

Presently, we are involved in undertstanding the quantum limits of estimating multiple parameteres simultanouesly. This provides a novel avenue for investigating interesting questions about incompatible and collective quantum measurements, and opens the way to high level applications such as field imaging and microscopy.

Potential students must have strong interests in quantum information theory, probability theory and quantum optics.

Quantum correlations : Identifying the resources that make quantum enhancements possible is an abiding question in quantum information science. Although quantum entanglement is generally believed and frequently claimed to be the main resource, it is not so in all cases. A rigorous proof only exists for the necessity of multipartite entanglement for exponential speedup in pure state quantum computation. What about mixed state quantum computation ? Or non-universal models such as the one pure qubit model, boson sampling, instantaneous quantum computing, and quantum simulation in general. And what about other information processing tasks like communication, cryptography, or sensing ?

We study measures of quantum correlations more general than quantum entanglement. The foremost is quantum discord, but by no means the sole one. We also study how such correlations can be generated and detected in principle, as well as in practice in physical systems. Another aspect is the opertational interpretation of these new measures in terms of quantum information processing tasks. We use the resource theory of quantum information and the family of quantum protocols such as the fully-quantum Slepian Wolf protocol. While these questions are typically studied in the context of finite dimensional systems, we are interested in continuous variable version was well, where non-Gaussianity plays a central role. This takes us deep into the heart of quantum information processing, opening up new ways of attaining quantum enhancements in information processing.

Research in the theory of quantum correlations requires tools from classical and quantum information theory of discrete and continuous variable systems.

Quantum biology : Whether quantum mechanics plays a role in life processes in an intriuging question. It surely does, since the stability of matter and the nature of chemical bonds are quantum mechanical. Indeed, any process analysed at a length scale short enough and time scale small enough will exhibit quantum behaviour. The first step in constuting a well-posed question is therefore to identify the phenomenon of interest, and then study the role of quantum mechanics on length and time scales relevant to the phenomenon.

We study the process of efficient energy transport in light-harvesting complexes. This is a vital part of photosynthesis, and operates at efficienceis of about 98-99 %. This extremely high efficiency cannot be explained by a classical model of energy transport across a network, leading some scientists to propose that quantum correlations might be playing a role. Since naturally occurring light-harvesting complexes are very complicated systems that cannot be modifed easily and arbitrarily, we design networks that can be constructed to abstract the process of energy transport on networks. These lessons can often be helpful in designing quantum information protocols in noisy scenarios. We also study novel spectroscopic techniques to detect the nature of quantum correlations in naturally occurring light-harvesting complexes.

Potential students must have strong interests in quantum optics, quantum nonlinear optics, quantum light-matter interactions and quantum information theory.

Quantum verification : If a quantum computer factorises a number so large that it has never been factorised before, the correctness of the answer be checked efficiently on a classical computer. However, if a quantum simulator performs a simulation so hard that it had never been simulated before, how do we assure ourselves of its correctness ?

We study non-universal models of quantum computation and simulation. This is done, such as for the verification of the one pure qubit model, using encoding via blindness which was used for verification of universal quantum computation. This ties in with delegated quantum computing within a server-verifier model, the standard paradigm of interactive proof systems in compter science. The degree of confidence in any given verification protocol also depends on the exact nature of encoding employed. Thus, we are led to studying some fundamental aspects of quantum error correcting codes.

Potential students must have strong interests in quantum information theory, quantum computation and error correction, and quantum simulations.