A question of reality

Date:
September 24, 2020
Source:
Springer
Summary:
Physicists have published a review that explores Bell's inequalities
and his concepts of reality and explains their relevance to quantum
information and its applications.



FULL STORY ========================================================================== Physicist Reinhold Bertlmann of the University of Vienna, Austria has
published a review of the work of his late long-term collaborator John
Stewart Bell of CERN, Geneva in EPJ H. This review, 'Real or Not Real:
that is the question', explores Bell's inequalities and his concepts
of reality and explains their relevance to quantum information and its applications.


==========================================================================
John Stewart Bell's eponymous theorem and inequalities set out,
mathematically, the contrast between quantum mechanical theories and
local realism. They are used in quantum information, which has evolving applications in security, cryptography and quantum computing.

The distinguished quantum physicist John Stewart Bell (1928-1990) is
best known for the eponymous theorem that proved current understanding
of quantum mechanics to be incompatible with local hidden variable
theories. Thirty years after his death, his long-standing collaborator
Reinhold Bertlmann of the University of Vienna, Austria, has reviewed
his thinking in a paper for EPJ H, 'Real or Not Real: That is the
question'. In this historical and personal account, Bertlmann aims to
introduce his readers to Bell's concepts of reality and contrast them
with some of his own ideas of virtuality.

Bell spent most of his working life at CERN in Geneva, Switzerland,
and Bertlmann first met him when he took up a short-term fellowship
there in 1978.

Bell had first presented his theorem in a seminal paper published in 1964,
but this was largely neglected until the 1980s and the introduction of
quantum information.

Bertlmann discusses the concept of Bell inequalities, which arise through thought experiments in which a pair of spin- 1/2 particles propagate
in opposite directions and are measured by independent observers, Alice
and Bob.

The Bell inequality distinguishes between local realism -- the 'common
sense' view in which Alice's observations do not depend on Bob's,
and vice versa - - and quantum mechanics, or, specifically, quantum entanglement. Two quantum particles, such as those in the Alice-Bob
situation, are entangled when the state measured by one observer instantaneously influences that of the other.

This theory is the basis of quantum information.

And quantum information is no longer just an abstruse theory. It
is finding applications in fields as diverse as security protocols, cryptography and quantum computing. "Bell's scientific legacy can be
seen in these, as well as in his contributions to quantum field theory," concludes Bertlmann. "And he will also be remembered for his critical
thought, honesty, modesty and support for the underprivileged."

========================================================================== Story Source: Materials provided by Springer. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Reinhold A. Bertlmann. Real or not real that is the question... The
European Physical Journal H, 2020; DOI: 10.1140/epjh/e2020-10022-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200924135342.htm

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