Real or Not Real that is the question

TL;DR

This paper reviews Bell's perspective on quantum reality, discusses Bell-type experiments and their implications, compares different interpretations of quantum states, and explores the concept of virtuality in quantum field theory, blending history and philosophy.

Contribution

It provides a historical overview of Bell's views, summarizes key experiments, and contrasts the realist and information-theoretic interpretations of quantum states.

Findings

Bell's experiments support nonlocality in quantum mechanics.

Different interpretations offer contrasting views on the nature of quantum states.

The concept of virtual particles adds a layer of complexity to understanding quantum reality.

Abstract

My discussions with John Bell about reality in quantum mechanics are recollected. I would like to introduce the reader to Bell's vision of reality which was for him a natural position for a scientist. Bell had a strong aversion against "quantum jumps" and insisted to be clear in phrasing quantum mechanics, his "words to be forbidden" proclaimed with seriousness and wit -- both typical Bell characteristics -- became legendary. I will summarize the Bell-type experiments and what Nature responded, and discuss the implications for the physical quantities considered, the real entities and the nonlocality concept due to Bell's work. Subsequently, I also explain a quite different view of the meaning of a quantum state, this is the information theoretic approach, focussing on the work of Brukner and Zeilinger. Finally, I would like to broaden and contrast the reality discussion with the concept of "virtuality", with the meaning of virtual particle occurring in quantum field theory. With some of my own thoughts I will conclude the paper which is composed more as a historical article than as a philosophical one.