Imperial College London

Professor Halliwell

Faculty of Natural SciencesDepartment of Physics

Professor in Theoretical Physics
 
 
 
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Contact

 

+44 (0)20 7594 7831j.halliwell

 
 
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Assistant

 

Mrs Graziela De Nadai-Sowrey +44 (0)20 7594 7843

 
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Location

 

521Huxley BuildingSouth Kensington Campus

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Summary

 

Summary

My broad interests over my whole career are the foundations of quantum mechanics and quantum gravity with my present focus being on questions concerning time in quantum mechanics.

I started out in 1983 in the relativity group in Cambridge and worked on quantum cosmology -- the attempt to describe models of the early universe in completely quantum-mechanical terms -- for ten years or more and this area still remains one of interest to me and a source of interesting problems in quantum theory. I subsequentlybecame interested in the decoherent histories approach to quantum theory, which is a novel formulation of standard quantum theory which gives histories a central role. This is of particular interest in quantum gravity, where the notorious problem of time makes it difficult to define a time-evolving state. It also provides an extremely powerful framework in which to address the emergence of classical behaviour from quantum theory, another area on which I have worked for many years, mainly in the context of non-relativistic quantum mechanics.

In the last few years I have worked extensively on aspects of time in quantum mechanics and associated phenomena, including the quantum Zeno effect and also the intriuging phenomenon of backflow -- the (so far unobserved) fact that for a state of purely positive momenta the probability can flow in the opposite direction. I also wrote a paper recentlly offering a sensible interpretation of negative probabilities and another on looking at Fine's theorem, which is essentially the logical converse of Bell's inequalities.

In the next few years I anticipate that I will be continuing to work on time in quantum mechanics, emergent classicality and general issues in the foundations of quantum mechanics.

Publications

Journals

Halliwell JJ, 2019, Leggett-Garg tests of macrorealism: checks for noninvasiveness and generalizations to higher-order correlators, Physical Review A, Vol:99, ISSN:1050-2947

Halliwell JJ, Hartle JB, Hertog T, 2019, What is the no-boundary wave function of the Universe?, Physical Review D, Vol:99, ISSN:2470-0010

Halliwell JJ, Beck H, Lee BKB, et al., 2019, Quasiprobability for the arrival-time problem with links to backflow and the Leggett-Garg inequalities, Physical Review A, Vol:99, ISSN:1050-2947

Dorronsoro JD, Halliwell JJ, Hartle JB, et al., 2018, Damped perturbations in the no-boundary state, Physical Review Letters, Vol:121, ISSN:0031-9007

Dorronsoro JD, Halliwell JJ, Hartle JB, et al., 2017, Real no-boundary wave function in Lorentzian quantum cosmology, Physical Review D, Vol:96, ISSN:2470-0010

More Publications