Special Lecture

V A Raghunathan, RRI, Bengaluru

Nobel Prize for Physics 2022: From Foundational Questions in Quantum Physics to Cutting Edge Technology of Today

The foundations of Quantum Mechanics, one of the most successful theoretical platforms for the description of nature, have been vigourously debated over the decades since its formulation. While its success is remarkable, it unsettles its practitioners with its stark deviations from many structures that define classical theories of physics. Questions with respect to the nature of physical reality and definiteness are among many issues that have haunted everyone, even its most esteemed practitioners. In the mid-1930’s Einstein, Podolsky and Rosen argued about the incompleteness of Quantum Mechanics as a descriptor of physical reality, a point that was strongly refuted by Bohr and others. In the mid-1960’s a paper by John Bell developed formalism which weighed in on concerns of the EPR paper and hidden variable formulations of quantum physics. An explicit inequality was derived that allowed experiments to be constructed, which could decide whether Quantum Mechanics was consistent with local realism or not. The experiments with correlated pairs of photons of Friedman and Clauser and Aspect, Grangier, Roger, and Dalibard, settled the debate by weighing against local realism. The work of Anton Zeilinger and his group has focussed on both core issues, in improvements and closing loopholes, and developing the science and technology forward to the point that the ideas and tools for Quantum Networks become viable. In this talk, I will discuss the physics problems from first principles and highlight how the pathbreaking experiments were done, which led to the Nobel Prize. The talk is intended for a general audience.