The possibility of explaining the objective physical reality of single-particle quantum systems in Young-Feynman double-slit interference experiments

In the Bell inequality–violating experiments that won the 2022 Nobel Prize in Physics, it was demonstrated that a two-particle quantum entangled system cannot preserve local realism. However, the very nature of realism for an isolated quantum system (a single-particle system) remains an open question.

In 1965, Feynman proposed the double-slit interference experiment (the hypothetical Young–Feynman experiment) to probe this mystery within the framework of wave–particle duality. Bohr’s principle of complementarity asserts that any given experimental arrangement can provide only one type of information—either about the wave nature or the particle nature. Based on this, the Copenhagen School inferred that quantum matter itself exists only probabilistically in either the wave or particle mode, and there is no way to determine whether they exist independently and objectively. Only when a measuring apparatus interacts with a microscopic particle does quantum matter manifest as either a wave or a particle. This is a form of subjective realism, dependent on the measurement setup chosen by the experimenter.

In the famous 1927 debate with Bohr, Einstein rejected the Copenhagen interpretation and consistently defended the realist viewpoint.

This presentation will provide an update on recent single-photon double-slit interference experiments, primarily carried out in Vietnam [1]. The results reveal that both wave-like and particle-like information can be simultaneously obtained in the same experiment. This, however, constitutes an evident contradiction of the principle of complementarity and leads to a rejection of some of the Copenhagen School’s fundamental arguments.

This new discovery requires us to recognize the objective reality of a single-particle quantum system. The report will also introduce a new theoretical framework aimed at addressing the shortcomings of the Copenhagen Interpretation in explaining the microscopic world [2]. We will discuss how such a new theoretical model must achieve consistency while preserving the opposing aspects of Relativity and Quantum Mechanics—specifically, the dichotomies of continuity–discreteness, determinism–indeterminism, causality–randomness, and locality–nonlocality.

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[1]    Vo Van Thuan, Vu Duc Vinh, Nguyen Thanh Hung, Dang Quang Thieu. Phys. Scr. 100 (2025) 055119.
[2]    Vo Van Thuan. Found. Phys. 47 (2017)1559.