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Physicists’ meet in Calcutta for ‘spooky action’

New Delhi, Jan. 4: Some of the world’s top physicists will gather in Calcutta this week to discuss a puzzle that emerged 75 years ago, pitted two 20th century giants in a philosophical duel, and continues to baffle as well as excite scientists today.

The S.N. Bose National Centre for Basic Sciences, Calcutta, is organising a conference on quantum entanglement, a concept that challenges commonsensical notions, but promises hacker-proof communications and immensely faster computers.

About 150 physicists from India and at least 10 other countries are expected to attend the conference to take stock of efforts to understand quantum entanglement as well as discuss possible applications of an idea yet to be fully fathomed.

“Quantum entanglement remains a big conceptual mystery, but we can already see emerging applications,” said Archan Majumdar, a physicist at the S.N. Bose Centre and convener of the conference.

Physicists and engineers have already demonstrated quantum cryptography — a method of preventing unauthorised access to information transfer that could make electronic communications far more secure than they are today.

A hacker with enough time and resources could, in principle, access information protected through conventional cryptography. “With quantum cryptography, even an attempt by the eavesdropper to look at information can be detected,” Majumdar told The Telegraph.

The idea of quantum entanglement emerged in a paper by Albert Einstein and his colleagues Boris Podolsky and Nathan Rosen in 1935. It implied that particles separated from each other — a pair of photons, say — can exchange information instantaneously.

Einstein, unhappy with the faster-than-light implications, dubbed the concept as “spooky-action-at-a-distance”, and said that it meant that the theory was incomplete. But the Danish physicist Neils Bohr — a quantum physics pioneer — disagreed.

This philosophical debate persisted until the northern Irish physicist John Bell reformulated the puzzle in 1964 in a way that allowed it to be experimentally tested in a laboratory, said Dipankar Home, a physicist at the Bose institute, also a convener of the conference.

A French physicist Alain Aspect whose experiments in 1982 settled the dispute between Einstein and Bohr — in favour of Bohr, by showing that spooky-action-at-a-distance does indeed occur — will be among physicists expected to attend the conference.

Aspect is expected to deliver a talk on how the applications of quantum entanglement may impact society during the 21st century just as did transistors and integrated circuits during the 20th century.

“The problem with quantum entanglement is that what we observe experimentally cannot be described in terms of our experiences in the real world unless we invoke spooky-action-at-a-distance — some secret, and faster-than-light communication between separated physical systems,” said C.S. Unnikrishnan, a physicist at the Tata Institute of Fundamental Research (TIFR), Mumbai, who’s presenting a paper at the conference.

“The puzzle persists — and it is a source of discomfort for some physicists,” he said.

But that hasn’t prevented physicists from pursuing applications — seeking to design quantum computers that may work at speeds exponentially faster than today’s fastest supercomputers, and trying to push a science fiction concept of teleportation into the realm of reality.

Quantum cryptography has already hit the market. The Geneva-based company ID Quantique and Australia’s Senetas Corporation last year provided quantum encryption techniques to secure a key communication link during the football World Cup between a stadium in Durban and an operations centre.

Gilles Brassard from the University of Montreal, one of the inventors of quantum cryptography, and Charles Bennett from IBM Research in the US, who has explored concepts of teleportation, are among the foreign delegates expected at the meet.

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