After the discovery of quantum mechanics by Heisenberg and Schrödinger in 1925, Einstein raised again and again objections to this theory. Obviously, he had the impression that (a) quantum mechanics does not adequately grasp reality, that it is (b) based on probabilistic laws of nature and that it is (c) for this reason incomplete. Einstein must have obtained this impression from many presentations of quantum mechanics in the first decade after its discovery. -- However, technical refutations of Einstein's objections were not possible when these arguments were put forward, since the necessary formal tools were not yet available at this time. Instead, the advocates of quantum mechanics tried to disprove Einstein merely by intuitive and less rigorous arguments. -- In the light of current physics we find that the objections (a) and (b) are irrelevant since, in accordance with Einstein's intentions, quantum mechanics does refer to reality and is not based on probabilistic laws. Only the incompleteness argument is incorrect. However, for technical reasons a convincing refutation of this objection only became possible thirty years after its formulation and ten years after Einstein's death.
After the discovery of quantum mechanics by Heisenberg and Schrödinger in 1925, Einstein raised again and again objections to this theory. Obviously, he had the impression that (a) quantum mechanics does not adequately grasp reality, that it is (b) based on probabilistic laws of nature and that it is (c) for this reason incomplete. Einstein must have obtained this impression from many presentations of quantum mechanics in the first decade after its discovery. -- However, technical refutations of Einstein's objections were not possible when these arguments were put forward, since the necessary formal tools were not yet available at this time. Instead, the advocates of quantum mechanics tried to disprove Einstein merely by intuitive and less rigorous arguments. -- In the light of current physics we find that the objections (a) and (b) are irrelevant since, in accordance with Einstein's intentions, quantum mechanics does refer to reality and is not based on probabilistic laws. Only the incompleteness argument is incorrect. However, for technical reasons a convincing refutation of this objection only became possible thirty years after its formulation and ten years after Einstein's death.
SUMMARY. — In this article, I examine Einstein's objections to quantum mechanics, with the formalism's interpretation in terms of complementarity as the historical setting. From 1924 to 1927, the period of development of a formalised quantum theory, Einstein raised certain questions that kept him from joining the throng of ardent supporters. Against the theory and its interpretation of 1927, he at first advanced arguments with the idea of eventually finding a flaw in quantum mechanics, and casting doubts upon its pretensions of completeness. Finally acknowledging, in 1931, the theory's coherence and accuracy at describing phenomena, he then tried to put forth objections to the theory's interpretation, which aimed at demonstrating the theory's incompleteness. These arguments culminated in the « Einstein-Podolsky-Rosen » article of 1935, and Einstein repeated them continually until his death. The analysis here calls, of course, for assessments of both the import of Einstein's arguments in relation to physics today, as well as to Einstein's own conceptions where theoretical physics is concerned, but these go beyond the aims of the present article.
This is an account of Einstein's work and thoughts on the quantum theory. The following topics will be discussed: The light-quantum hypothesis and its gradual evolution into the photon concept. Early history of the photoelectric effect. The theoretical and experimental reasons why the resistance to the photon was stronger and more protracted than for any other particle proposed to date. Einstein's position regarding the Bohr-Kramers-Slater suggestion, the last bastion of resistance to the photon. Einstein's analysis of fluctuations around thermal equilibrium and his proposal of a duality between particles and waves, in 1909 for electromagnetic radiation (the first time this duality was ever stated) and in January 1925 for matter (prior to quantum mechanics and for reasons independent of those given earlier by de Broglie). His demonstration that long-known specific heat anomalies are quantum effects. His role in the evolution of the third law of thermodynamics. His new derivation of Planck's law in 1917 which also marks the beginning of his concern with the failure of classical causality. His role as one of the founders of quantum statistics and his discovery of the first example of a phase transition derived by using purely statistical methods. His position as a critic of quantum mechanics. Initial doubts on the consistency of quantum mechanics (1926-1930). His view maintained from 1930 until the end of his life: quantum mechanics is logically consistent and quite successful but it is incomplete. His attitude toward success. His criterion of objective reality. Differences in the roles relativity and quantum theory played in Einstein's life. His vision regarding quantum theory in the context of a unified field theory. His last autobiographical sketch, written a few months before his death, concluding with a statement about the quantum theory, a subject to which (by his own account) he had given more thought than even to general relativity.
From a phenomenological and experimental viewpoint, quantum mechanics is remarkably successful in explaining effects and processes in the microscopic world. Recently, however, a growing body of literature has revisited the theory's own formal foundations, specifically addressing issues of self-consistency and completeness. As a major historical example of these foundational challenges, the Einstein-Podolsky-Rosen (EPR) argument famously claimed that the theory is incomplete. While many valid criticisms and refutations of the EPR logic exist, they generally rely on a combination of technical results and conceptual objections to EPR's interpretive assumptions, thus transcending the plain quantum framework itself. Motivated by these trends of examining the theory's structural limits, here we revisit the EPR argument. Focusing on elements essential to the EPR reasoning, we first analyze general quantum correlations for EPR states: (i) the fact that their observables are always associated with non-commuting operators, and (ii) the nature of the correlated information obtained through measurement. From these two points alone, and relying strictly on the core rules of quantum mechanics, we demonstrate how to overturn the alleged EPR incompleteness without invoking any extraneous propositions. Consequently, we show that the standard formalism alone suffices to resolve such type of skepticism regarding the theory's physical reach. This offers, at least in a paradigmatic instance, a powerful indication of a structurally well-founded, self-consistent quantum theory.
Elements of quantum mechanics Quantum mechanics was discovered in 1925 through groping efforts to compromise two apparently contradictory pictures on the fundamental entities in nature. One was the wave picture for light which was later extended to matter by de Broglie, another was the corpuscular picture of matter which was later extended to light by Einstein. Schrödinger's wave equation came as a natural development of the first stream, while Heisenberg's matrix mechanics was presented as a unique proposal from the second stream. In spite of completely different appearances, the two theories proved, within a couple of years after their discoveries, to be equivalent. This is a most beautiful example that the physical reality exists independent of the mathematical framework formulated for its description. In this chapter, we will give a very brief review of the principles of quantum mechanics, 1–3 mainly with the harmonic oscillator as a model system for the following reasons. The first is historical: the electromagnetic wave, whose interaction with matter is the subject of this book, is a harmonic oscillator, a system which was for the first time subject to “quantization”, thus opening a way to the discovery of quantum mechanics. The second is technical: the harmonic oscillator is one of very few examples of analytically soluble problems in quantum mechanics. The third is pedagogical: the harmonic oscillator is a system best suited for realization of the equivalence of the two different pictures mentioned above and hence for a deeper understanding of the principles of quantum mechanics.
Quantum theory is considered as the most successful scientific theory of all time. However, the understanding1 and interpretation of quantum theory has been subjected to a continuous debate since its formulation. A leading role was played by Einstein in the development of the old quantum theory but he was not impressed by the statistical interpretation of the quantum theory. He believed in a world of well defined law and order in which objectivity exists. He never thought that the new quantum theory as a complete theory. In 1926 in a letter to Max Born, Einstein wrote: Quantum mechanics is very impressive. ... The theory produces good deal but hardly brings us closer to the secret of the old one. I am at all events convinced that God does not play dice.
The foundations and meaning of quantum theory became a central issue to Albert Einstein and Niels Bohr since the onset of their impassioned debate in the 1920s, enriched by the contributions of many other distinguished scientists and philosophers.The questions are not settled down at all, despite the great achievements of the theory, its impressive accordance with experiment and predictive power.The fundamental and technological applications range from cosmology to biology, with the development of invaluable instruments and the design of new materials.Is quantum mechanics a complete or an incomplete theory?Is there an objective reality independent of the observer or is the reality created by the measurements?Are hidden-variable theories justifiable?Is there a quantum theory founded in a local-causal and non-linear approach that formally contains the orthodox linear theory as a special case?Can such a formulation unify classical and quantum physics?Are Heisenberg's uncertainty relations valid in all cases?Here, the subject is addressed as an adaptation of our contribution to the Colloquium "Quantal aspects in Chemistry and Physics.