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George Knee

I completed my doctorate at the University of Oxford in 2014, and have held postdocs there and at NTT Basic Research Laboratories in Japan. Since 2016 I now hold a Research Fellowship from the Royal Commission for the Exhibition of 1851. My main interests revolve around quantum theory and quantum technology:

Foundations of quantum theory. I am interested in how quantum mechanics can go beyond any classical theory. Experimental tests may look to expose characteristic aspects of non-locality or of superposition in a variety of physical systems. I have been involved in designing such tests in photonic, solid-state and superconducting quantum computing architectures, and am currently involved in efforts to design such tests on bio-molecular systems. This is in an attempt to strive towards an implementation of the famous Schroedinger 'cat paradox', where a macroscopic, living organism is placed into a quantum state: for example, with the interpretation that a cat can be both dead and alive simultaneously. Is this possible, even in principle? Or are there fundamental laws prohibiting it?

Flux qubit and cat

It is fascinating to ask: have living organisms evolved to exploit the advantages the quantum mechanics can bring? One example is in the transport of energy through pigment-protein complexes, an important function of natural light harvesting systems. We use quantum dynamics modelling and statistical analysis, as well as simulations of ultrafast multidimensional spectroscopy experiments in order to try and answer this question.

I have also worked on the issue of whether quantum states may be interpreted as states of knowledge, rather than as a true part of physical reality. This appealing idea would solve many interpretational issues at the heart of quantum theory: but unfortunately appears to have limited validity.

Ontological model of quantum state preparation

Quantum metrology. Quantum states tend to be extremely fragile, in the sense that they are disturbed by even very weak interactions with the surrounding environment. This is a major disadvantage in many applications, but can be turned into a positive if one wishes to sense those weak interactions. Theoretical work suggests that highly entangled states would be particularly useful, for example for sensing magnetic fields. I try to figure out whether other quantum (or quantum-inspired) techniques can help: for example a technique known as 'weak value amplification'. This technique uses a gentle measurement and postselection to amplify small signals.

Hong Ou Mandel interferometer

It is very important to investigate whether such advantages can persist in the presence of detector imperfections. Hong-Ou-Mandel interferometry is a particularly robust approach to sensing the thickness of a transparent object, and involves the interference of a pair of identical bosons. Recently, samples were experimentally measured down to attosecond (nanometre) resolution.

Quantum computing. Quantum computers promise to revolutionise information processing for many applications, most famously for code breaking. Quantum simulation is perhaps a more exciting application, since it provide answers in physics and chemistry research that are currently effectively impossible to compute. While code breaking may require a very large quantum computer with immaculately low error rates, quantum simulation may start to be useful even on small-scale and noisy quantum computers. Such devices should become available in the near future -- but how can we trust their output? I am working towards techniques for optimising the precision of such devices, and to try and quantify the trustworthiness of such computations.

When considering the ultimate limits of quantum technologies, and when calculating important quantities such as the degree of entanglement or coherence in a quantum state, it is very useful to have a complete mathematical description. Reconstructing this description from laboratory data is known as quantum state tomography. I am interested in classical algorithms that aid in this computationally expensive task.

The set of physical states

For a full list of publications please see Google Scholar.

George Knee

Email: G.Knee "at" warwick.ac.uk

Phone: 024 761 50943

Office: PS139

Address: Department of Physics, University of Warwick, Coventry, CV4 7AL

Google Scholar page.

Quantum Information Science Group