Simone Severini

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Simone Severini
NationalityItalian, British
Education University of Bristol (PhD)
Alma mater University of Florence
Known for Braunstein-Ghosh-Severini Entropy
Induced gravity
Quantum contextuality
Awards Royal Society University Research Fellowship
Newton International Fellowship
Scientific career
Fields Physics, Computer Science, Quantum Computing
Institutions UCL
Institute for Quantum Computing
Doctoral advisor Richard Jozsa [1]
Website www.ucl.ac.uk/~ucapsse

Simone Severini is an Italian-born British computer scientist. He is currently Professor of Physics of Information at University College London, and Director of Quantum Computing at Amazon Web Services.

Contents

Work

Severini worked in quantum information science and complex systems. Together with Adan Cabello and Andreas Winter, he defined a graph-theoretic framework for studying quantum contextuality, and together with Tomasz Konopka, Fotini Markopoulou, and Lee Smolin, he introduced a random graph model of spacetime called quantum graphity. [2] [3] He served as an editor of Philosophical Transactions of the Royal Society A. In 2015 he was one of the first scientific advisors of Cambridge Quantum Computing, with Béla Bollobás, Imre Leader, and Fernando Brandão. In network theory, he co-introduced the Braunstein–Ghosh–Severini entropy, [4] with applications to quantum gravity.

Publications

Related Research Articles

<span class="mw-page-title-main">Quantum gravity</span> Description of gravity using discrete values

Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics. It deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the vicinity of black holes or similar compact astrophysical objects, such as neutron stars as well as in the early stages of the universe moments after the Big Bang.

A wormhole is a hypothetical structure connecting disparate points in spacetime, and is based on a special solution of the Einstein field equations.

<span class="mw-page-title-main">Loop quantum gravity</span> Theory of quantum gravity, merging quantum mechanics and general relativity

Loop quantum gravity (LQG) is a theory of quantum gravity, which aims to reconcile quantum mechanics and general relativity, incorporating matter of the Standard Model into the framework established for the intrinsic quantum gravity case. It is an attempt to develop a quantum theory of gravity based directly on Einstein's geometric formulation rather than the treatment of gravity as a mysterious mechanism (force). As a theory, LQG postulates that the structure of space and time is composed of finite loops woven into an extremely fine fabric or network. These networks of loops are called spin networks. The evolution of a spin network, or spin foam, has a scale above the order of a Planck length, approximately 10−35 meters, and smaller scales are meaningless. Consequently, not just matter, but space itself, prefers an atomic structure.

Doubly special relativity (DSR) – also called deformed special relativity or, by some, extra-special relativity – is a modified theory of special relativity in which there is not only an observer-independent maximum velocity, but also, an observer-independent maximum energy scale and/or a minimum length scale. This contrasts with other Lorentz-violating theories, such as the Standard-Model Extension, where Lorentz invariance is instead broken by the presence of a preferred frame. The main motivation for this theory is that the Planck energy should be the scale where as yet unknown quantum gravity effects become important and, due to invariance of physical laws, this scale should remain fixed in all inertial frames.

<span class="mw-page-title-main">Fotini Markopoulou-Kalamara</span> Greek physicist (born 1971)

Fotini G. Markopoulou-Kalamara is a Greek theoretical physicist interested in quantum gravity, foundational mathematics, quantum mechanics and a design engineer working on embodied cognition technologies. Markopoulou is co-founder and CEO of Empathic Technologies. She was a founding faculty member at Perimeter Institute for Theoretical Physics and was an adjunct professor at the University of Waterloo.

In the interpretation of quantum mechanics, a local hidden-variable theory is a hidden-variable theory that satisfies the principle of locality. These are models, usually deterministic, that attempt to account for the probabilistic features of quantum mechanics via the mechanism of underlying inaccessible variables, with the additional requirement that distant events be statistically independent. Local hidden-variable theories automatically rule out instantaneous effects between separate events.

<span class="mw-page-title-main">Quantum field theory in curved spacetime</span> Extension of quantum field theory to curved spacetime

In theoretical physics, quantum field theory in curved spacetime (QFTCS) is an extension of quantum field theory from Minkowski spacetime to a general curved spacetime. This theory uses a semi-classical approach; it treats spacetime as a fixed, classical background, while giving a quantum-mechanical description of the matter and energy propagating through that spacetime. A general prediction of this theory is that particles can be created by time-dependent gravitational fields (multigraviton pair production), or by time-independent gravitational fields that contain horizons. The most famous example of the latter is the phenomenon of Hawking radiation emitted by black holes.

Induced gravity is an idea in quantum gravity that spacetime curvature and its dynamics emerge as a mean field approximation of underlying microscopic degrees of freedom, similar to the fluid mechanics approximation of Bose–Einstein condensates. The concept was originally proposed by Andrei Sakharov in 1967.

The Alternative models to the Standard Higgs Model are models which are considered by many particle physicists to solve some of the Higgs boson's existing problems. Two of the most currently researched models are quantum triviality, and Higgs hierarchy problem.

Numerical relativity is one of the branches of general relativity that uses numerical methods and algorithms to solve and analyze problems. To this end, supercomputers are often employed to study black holes, gravitational waves, neutron stars and many other phenomena governed by Einstein's theory of general relativity. A currently active field of research in numerical relativity is the simulation of relativistic binaries and their associated gravitational waves.

Samuel Leon Braunstein is a professor at the University of York, UK. He is a member of a research group in non-standard computation, and has a particular interest in quantum information, quantum computation and black hole thermodynamics.

<span class="mw-page-title-main">String-net liquid</span> Condensed matter physics model involving only closed loops

In condensed matter physics, a string-net is an extended object whose collective behavior has been proposed as a physical mechanism for topological order by Michael A. Levin and Xiao-Gang Wen. A particular string-net model may involve only closed loops; or networks of oriented, labeled strings obeying branching rules given by some gauge group; or still more general networks.

Sundance Osland Bilson-Thompson is an Australian theoretical particle physicist. He has developed the idea that certain preon models may be represented topologically, rather than by treating preons as pointlike particles. His ideas have attracted interest in the field of loop quantum gravity, as they may represent a way of incorporating the Standard Model into loop quantum gravity. This would make loop quantum gravity a candidate theory of everything.

The world crystal is a theoretical model in cosmology which provides an alternative understanding of gravity proposed by Hagen Kleinert.

Lorentz invariance follows from two independent postulates: the principle of relativity and the principle of constancy of the speed of light. Dropping the latter while keeping the former leads to a new invariance, known as Fock–Lorentz symmetry or the projective Lorentz transformation. The general study of such theories began with Fock, who was motivated by the search for the general symmetry group preserving relativity without assuming the constancy of c.

In network theory, the Braunstein–Ghosh–Severini entropy of a network is the von Neumann entropy of a density matrix given by a normalized Laplacian matrix of the network. This definition of entropy does not have a clear thermodynamical interpretation. The BGS entropy has been used in the context of quantum gravity.

Quantum contextuality is a feature of the phenomenology of quantum mechanics whereby measurements of quantum observables cannot simply be thought of as revealing pre-existing values. Any attempt to do so in a realistic hidden-variable theory leads to values that are dependent upon the choice of the other (compatible) observables which are simultaneously measured. More formally, the measurement result of a quantum observable is dependent upon which other commuting observables are within the same measurement set.

In theoretical physics, the problem of time is a conceptual conflict between general relativity and quantum mechanics in that quantum mechanics regards the flow of time as universal and absolute, whereas general relativity regards the flow of time as malleable and relative. This problem raises the question of what time really is in a physical sense and whether it is truly a real, distinct phenomenon. It also involves the related question of why time seems to flow in a single direction, despite the fact that no known physical laws at the microscopic level seem to require a single direction. For macroscopic systems the directionality of time is directly linked to first principles such as the second law of thermodynamics.

Continuous-variable (CV) quantum information is the area of quantum information science that makes use of physical observables, like the strength of an electromagnetic field, whose numerical values belong to continuous intervals. One primary application is quantum computing. In a sense, continuous-variable quantum computation is "analog", while quantum computation using qubits is "digital." In more technical terms, the former makes use of Hilbert spaces that are infinite-dimensional, while the Hilbert spaces for systems comprising collections of qubits are finite-dimensional. One motivation for studying continuous-variable quantum computation is to understand what resources are necessary to make quantum computers more powerful than classical ones.

Relativistic quantum cryptography is a sub-field of quantum cryptography, in which in addition to exploiting the principles of quantum physics, the no-superluminal signalling principle of relativity theory stating that information cannot travel faster than light is exploited too. Technically speaking, relativistic quantum cryptography is a sub-field of relativistic cryptography, in which cryptographic protocols exploit the no-superluminal signalling principle, independently of whether quantum properties are used or not. However, in practice, the term relativistic quantum cryptography is used for relativistic cryptography too.

References

  1. Mathematics Genealogy Project
  2. Roberto Mangabeira Unger, Lee Smolin, The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy, Cambridge University Press (2014).
  3. Shyam Wuppuluri and Giancarlo Ghirardi (Eds.), Space, Time and the Limits of Human Understanding (Foreword by John Stachel and Afterword by Noam Chomsky), Springer (2017).
  4. Braunstein, Samuel L.; Ghosh, Sibasish; Severini, Simone (2006). "The Laplacian of a Graph as a Density Matrix: A Basic Combinatorial Approach to Separability of Mixed States". Annals of Combinatorics . Springer Science and Business Media LLC. 10 (3): 291–317. arXiv: quant-ph/0406165 . doi:10.1007/s00026-006-0289-3. ISSN   0218-0006. S2CID   14522309.