Sandu Popescu

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Sandu Popescu

Sandu Popescu (* 1956 in Oradea , Romania ) is a British physicist who studies quantum information theory and the fundamentals of quantum mechanics .

life and work

Popescu studied with Yakir Aharonov in Tel Aviv. He is a professor at the University of Bristol (HH Wills Laboratory) and has been a visiting professor at the University of California, Berkeley .

He is particularly concerned with quantum non-locality . He works mainly theoretically, but also experimentally and was also involved in commercial applications.

In 1992 he and Daniel Rohrlich (at the time at the Free University of Brussels) found quantum states that violate Bell's inequality to the maximum. But they also found entangled quantum states that do not violate Bell's inequality. In 1994 he showed that if one takes nonlocality instead of indeterminacy as a basis, there are theories that violate the CHSH inequalities (generalizations of the Bell inequalities by John Clauser , Horne, Shimony and Holt) more than is permitted by quantum mechanics. These superquantum correlations still fulfill the relativistic causality (no information exchange with faster than light speed). Quantum mechanics provides bounds on the amount of inequalities for the CHSH (local hidden variable theories with a value of 2), the states discovered by Popescu and Rohrlich (nonlocal PR boxes) meet the maximum allowable limit 4. They are in principle observable (but have so far been no such states found) and have theoretical application, for example in the investigation of security in quantum cryptography.

From 1996 to 2008 he was at Hewlett-Packard , which has a research laboratory near Bristol. There he and others realized quantum teleportation in 1997 as one of the first in a quantum optical experiment.

One of the non-intuitive conclusions of quantum theory is his discovery with Nicolas Gisin that two antiparallel spins contain more information about their direction than parallel spins (the reason is the anti-unitarity of the spin inversion). With Gisin and other colleagues, he introduced quantum gloves , pairs of rotationally invariant quantum states that contain complete information about the chirality of a three-dimensional reference system, but no information about its orientation. He thus examines the difference between information content and physical realization.

Most recently he has been studying the thermodynamics of quantum systems. In particular, he showed that even very small quantum systems (made up of 2 qubits) can achieve the Carnot efficiency of thermodynamic machines.

In 2000 he received the Adams Prize and in 2011 he received the John Stewart Bell Prize from the University of Toronto. For 2016 he was awarded the Dirac Medal of the Institute of Physics , in 2017 he was elected to the Royal Society .

Fonts

  • with H.-K. Lo, T. Spiller (Editor) Introduction in quantum information and computation , World Scientific, 1998

In addition to the articles and articles cited in the footnotes. a .:

  • Sandu Popescu, Noah Linden, Anthony Short, Andreas Winter: Quantum nonlocality and beyond: Limits from nonlocal computation . In: Phys. Rev. Lett. tape 99 , 2007, p. 180502 , arxiv : quant-ph / 0610097 .
  • Jonathan Barrett, Noah Linden, Serge Massar, Stefano Pironio, Sandu Popescu, David Roberts: Non-local correlations as an information theoretic resource . In: Phys. Rev. A . tape 71 , 2005, p. 022101 , arxiv : quant-ph / 0404097 .

Web links

Individual evidence

  1. ^ S. Popescu, D. Rohrlich: Which states violate Bell's inequality maximally? In: Phys. Lett. A . tape 169 , 1992, pp. 411-414 , doi : 10.1016 / 0375-9601 (92) 90819-8 .
  2. ^ S. Popescu, D. Rohrlich: Generic quantum nonlocality . In: Phys. Lett. A . tape 166 , 1992, pp. 293-297 , doi : 10.1016 / 0375-9601 (92) 90711-T .
  3. ↑ Aharonov had previously proposed non-locality and relativistic causality as basic axioms for building quantum theory
  4. ^ Popescu, Rohrlich: Quantum Nonlocality as an axiom . In: Foundations of Physics . tape 24 , 1994, pp. 379-385 , arxiv : quant-ph / 9508009 .
  5. ↑ In 1997 Anton Zeilinger and colleagues also demonstrated quantum teleportation. It was first proposed by Charles H. Bennett et al. a. 1993.
  6. ↑ Boschi, Branca, De Martini, Hardy, Popescu: Experimental Realization of Teleporting an Unknown Pure Quantum State via Dual Classical and Einstein-Podolsky-Rosen Channels . In: Phys. Rev. Lett. tape 80 , 1998, pp. 1121 , arxiv : quant-ph / 9710013 .
  7. ^ N. Gisin, S. Popescu: Spin flips and quantum information for anti-parallel spins . In: Phys. Rev. Lett. tape 83 , 1999, pp. 432 , arxiv : quant-ph / 9901072 .
  8. ↑ D. Collins, L Diosi, N. Gisin, S. Massar, S. Popescu: Quantum gloves . In: Phys. Rev. A . tape 72 , 2005, p. 022304 , arxiv : quant-ph / 0409221 .
  9. ^ Popescu, Anthony J. Short, Andreas Winter: Entanglement and the Foundations of Statistical Mechanics . In: Nature Physics . tape 2 , 2006, p. 754-758 , arxiv : quant-ph / 0511225 .
  10. ^ Noah Linden, Popescu, Anthony J. Short, Andreas Winter: Quantum mechanical evolution towards thermal equilibrium . In: Phys. Rev. E . tape 79 , 2009, p. 061103 , arxiv : 0812.2385 .
  11. ^ Linden, Popescu, Skrzypczyk: How small can thermal machines be? The smallest possible refrigerator . In: Phys. Rev. Lett. tape 105 , 2010, p. 130401 , arxiv : 0908.2076 . , Linden, Popescu, Skrzypczyk: The smallest possible heat engines . 2010, arxiv : 1010.6029 .
  12. ↑ John Stewart Bell Prize 2013 for Popescu
  13. ↑ Sandu Popescu. In: Fellows Directory, Royal Society. Retrieved November 21, 2018 .
personal data
SURNAME Popescu, Sandu
BRIEF DESCRIPTION British physicist
DATE OF BIRTH 1956
PLACE OF BIRTH Oradea