I am a physics group leader at Royal Holloway, University of London.
My research is on connections between quantum information and high-energy physics. In particular, I am interested in how we could soon test quantum gravity in an experiment using tools of quantum information science. Please scroll through the rest of my website to learn more.
My group works at the crossover of quantum information science and high-energy physics, particularly on how we can use quantum technology to test fundamental physics. We predominantly study how quantum technology can be used to test the fundamental nature of gravity.
Most believe that gravity, like the other interactions, must be quantized, such that spacetime configurations can be in quantum superpositions. However, because gravity cannot be quantized via the same techniques we used for the other interactions (perturbative quantum field theory), some believe that gravity should remain classical, such that we cannot have quantum superpositions of spacetime geometry. There is also evidence that, by treating gravity as classical, we are led to a unified theory where classical mechanics emerges from quantum mechanics at macroscopic scales, solving the measurement paradox of quantum mechanics.
We consider experiments that could teach us the answer to whether gravity is quantized, as in theories such as String Theory or Loop Quantum Gravity, or if it is classical. Such experiments include looking for entanglement between mesoscopic quantum masses, or quantum non-Gaussianity in a gravitationally self-interacting Bose-Einstein condensate. In my group, emphasis is placed on low-temperature condensed matter systems, such as quantum gases, and alternative methods to looking for entanglement, but we are also interested in more standard approaches. In particular, we are interested in the assumptions that go into these tests and what the outcome of the tests can really teach us about how quantum theory and general relativity combine.
I joined the University of Vienna as a post-doctoral researcher in
2016 under the supervision of Professor Ivette Fuentes. At Vienna, I predominantly researched relativistic quantum information, looking
at how classical curved spacetime influences quantum information properties such as entanglement.
In particular, I studied how these influences could be used
in experiments, such as a novel gravitational wave detector
of micro-metre size.
While at Vienna, I taught undergraduate and
postgraduate courses in quantum optics and relativistic
quantum information.
Below is an overview of my career, for more detail see my CV.
© RH
I joined the University of Nottingham as a post-doctoral researcher in 2017, initially under the supervision of Professor Ivette Fuentes and then later Professor Gerardo Adesso.
My work at Nottingham included developing a new way to test a theory suggested by Sir Roger Penrose for combining quantum mechanics and general relativity, which was inspired by notions of quantum field theory in curved spacetime. This culminated in this publication.
Towards the end of my time at Nottingham, I hit upon a new idea for how to test quantum gravity with quantum technology. The idea is that we can use quantum non-Gaussianity rather than entanglement, which was, at the time, the conventional route of testing quantum gravity, essentially introduced first by Feynman, and later made concrete by the publications here and here. Using non-Gaussianity, we developed a new experimental proposal for testing quantum gravity that relied on just a single Bose-Einstein condensate. The publication can be found here.
© RH
I joined the University of Hong Kong in 2020,
under the supervision of Professor Giulio Chiribella,
just after the world-wide pandemic began!
I, together with a few colleagues, lived on the
tropical, jungle-like Lamma Island (pictured here).
While at Hong Kong, I continued to explore my new direction of connections between quantum gravity and quantum information. This included exploring the consequences of quantum black holes on quantum information, and the assumptions behind testing quantum gravity with entanglement, resulting in a proposal for a relativistic test of quantum gravity in the laboratory - see here.
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I joined the University of Oxford as a senior post-doctoral researcher in 2021. This was like returning home as I also undertook my combined undergraduate and masters in physics here.
I further explored how quantum information and technology can be used to test quantum gravity, finishing projects begun in Hong Kong and beginning and undertaking new projects. This included developing a new proposal for testing quantum gravity where two adjacent atom interferometers become entangled through their gravitational interaction. Evidence was found that this proposal could be closer to realization than traditional proposals based on quantum solids - see here.
I also looked deeper into the underlying assumptions of entanglement being a test of quantum gravity, finding, with my collaborators that the so-called "locality" assumption holds in a simplified version of quantum gravity in the most-studied proposal. However, this work - see here - indicates that this assumption might not hold in all proposed experiments.
I joined Royal Holloway, University of London (RHUL) as a group leader in March 2023.
Please see the page above on my group at RHUL. The group's website is currently under the process of construction.
I, and by association, RHUL are part of the QISS (Quantum Information Structure of Spacetime) consortium, of which I am also a member of the organizing committee and have various roles such as the manager of the cross-consortium visiting programme and providing guidance on the overall budget. The aims of QISS are closely connected to the interests of my group and provided funding to help with the creation of my group.
© RH
For a full list of publications, please see here
Selected Publications:
Quantum-enhanced screened dark energy detection
D Hartley, C Kading, RH, I Fuentes
European Physical Journal C: Particles and Fields (2024)
Relativistic locality can imply subsystem locality
A Di Biagio, RH, C Brukner, C Rovelli, M Christodoulou
arXiv preprint arXiv:2305.05645 (2023)
Gravitationally-induced entanglement in cold atoms
RH, N Cooper, L Hackermüller
arXiv preprint arXiv:2304.00734 (2023)
Locally Mediated Entanglement in Linearized Quantum Gravity
(previously called "Locally mediated entanglement through gravity from first principles")
M Christodoulou, A Di Biagio, M Aspelmeyer, Č Brukner, C Rovelli, RH
Physical Review Letters, 130, 10, 100202 (2023)
Gravity entanglement, quantum reference systems, degrees of freedom
M Christodoulou, A Di Biagio, RH, C Rovelli
Classical and Quantum Gravity 40 (4), 047001 (2023)
Non-Gaussianity as a Signature of a Quantum Theory of Gravity
(previously called "Testing quantum gravity with a single quantum system")
RH, V Vedral, D Naik, M Christodoulou, C Rovelli, A Iyer
PRX Quantum 2 (1), 010325 (2021)
Exploring the unification of quantum theory and general relativity with a Bose–Einstein condensate
RH, R Penrose, I Fuentes
New Journal of Physics 21 (4), 043047 (2019)
Quantum frequency interferometry: With applications ranging from gravitational wave detection to dark matter searches
RH, I Fuentes
AVS Quantum Science, 5, 1 (2023)
Quantum gravity as a communication resource
RH, A Akil, H Kristjánsson, X Zhao, G Chiribella
arXiv preprint arXiv:2203.05861 (2021)
Quantum simulation of dark energy candidates
D Hartley, C Käding, RH, I Fuentes
Physical Review D 99 (10), 105002 (2019)
Dynamical response of Bose–Einstein condensates to oscillating gravitational fields
D Rätzel, RH, J Lindkvist, I Fuentes
New Journal of Physics 20 (7), 073044
Analogue simulation of gravitational waves in a 3-dimensional Bose-Einstein condensate
D Hartley, T Bravo, D Rätzel, RH, I Fuentes
Physical Review D 98 (2), 025011 (2018)
Gravity in the quantum lab
RH, L Hackermüller, DE Bruschi, I Fuentes
Advances in Physics: X 3 (1), 1383184 (2018)
Quantum decoherence of phonons in Bose–Einstein condensates
RH, C Sabín, L Hackermüller, I Fuentes
Journal of Physics B: Atomic, Molecular and Optical Physics 51 (1), 015303
Minimal E6 supersymmetric standard model
RH, SF King
Journal of High Energy Physics 2008 (01), 030
Planck scale unification in a supersymmetric standard model
RH, SF King
Physics Letters B 652 (5-6), 331-337
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My virtual "QISS" seminar on how non-Gaussianity and Bose-Einstein condensates can be used to test quantum gravity can be found here
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My talk at the QISS 2022 conference at Western University on how we can test quantum gravity in table-top experiments and the different ideas on this can be found here.
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My talk at the QISS 2020 conference on how non-Gaussianity and continuous variables could be useful for testing quantum gravity can be found here.
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My talk at ZARM on the assumptions behind entanglement as a test of quantum gravity can be found here.
Please get in touch by emailing me at richard.howl@rhul.ac.uk