This preprint re-examines the widespread belief that “Einstein was wrong about quantum mechanics.” While Einstein is often portrayed as rejecting quantum theory due to his criticism of its probabilistic interpretation, this simplified narrative does not accurately reflect his actual position or the historical context. The paper organizes Einstein’s original arguments, clarifies common misunderstandings—such as the misattribution that he “advocated hidden variables”—and reviews the development of Bell’s inequalities and their experimental tests. These experiments ruled out simple local hidden-variable models but did not fully resolve Einstein’s deeper concern: the possible incompleteness of quantum mechanics as a physical theory. By revisiting historical documents and theoretical developments, this work argues that Einstein’s critique was not a fundamental mistake but has been misinterpreted over time. The goal is to provide a more accurate understanding of the Einstein–Bohr debates and the conceptual foundations of quantum mechanics.
This preprint re-examines the widespread belief that “Einstein was wrong about quantum mechanics.” While Einstein is often portrayed as rejecting quantum theory due to his criticism of its probabilistic interpretation, this simplified narrative does not accurately reflect his actual position or the historical context. The paper organizes Einstein’s original arguments, clarifies common misunderstandings—such as the misattribution that he “advocated hidden variables”—and reviews the development of Bell’s inequalities and their experimental tests. These experiments ruled out simple local hidden-variable models but did not fully resolve Einstein’s deeper concern: the possible incompleteness of quantum mechanics as a physical theory. By revisiting historical documents and theoretical developments, this work argues that Einstein’s critique was not a fundamental mistake but has been misinterpreted over time. The goal is to provide a more accurate understanding of the Einstein–Bohr debates and the conceptual foundations of quantum mechanics.
The support of Copenhagen quantum mechanics in the discussion concerning EPR experiments has been based fundamentally on two mistakes. First, quantum mechanics as well as hidden-variable theory give the same predictions; the statement of Belinfante from 1973 about the significant difference must be denoted as mistake. Secondly, the experimental violation of Bell's inequalities has been erroneously interpreted as excluding the hidden-variable alternative, while they have been based on assumption corresponding to classical physics. The EPR experiments cannot bring, therefore, any decision in the controversy between Einstein and Bohr. However, the view of Einstein is strongly supported by experimental results concerning the light transmission through three polarizers.
Lying at the heart of quantum mechanics, the notion of quantum superposition causes enormous difficulty in understanding the problem of quantum measurement, which concerns the Einstein-Bohr debate on the conceptual foundations of the quantum theory. According to Bell’s theorem, Einstein’s viewpoint in his debate with Bohr seems to be wrong. In the present paper, a new principle (referred to as the general principle of measurements) is introduced and proved as a mathematical theorem. Based on this principle, various forms of quantum superposition (including quantum entanglement) and the corresponding experiments are scrutinized. The main findings are as follows. (a) Einstein’s viewpoint is correct and Bell’s theorem is problematic. (b) Measurement outcomes of any actual experiment with individual microscopic objects described in a form of quantum superposition, in particular, the experimental results of testing Bell inequalities, are all erroneously explained. (c) Bell inequalities failed to capture the essence of the Einstein-Bohr debate, i.e., whether quantum superposition is legitimate for describing individual microscopic objects. (d) All kinds of quantum superposition violate the general principle of measurements and hence are illegitimate. (e) Quantum mechanics can be completed by using disjunction (“or”) as the logical relation between the orthonormal vectors that span an arbitrarily given Hilbert space for describing a single microscopic object, and the mathematical setting will remain essentially unchanged; hidden-variable theories are irrelevant to the real world. (f) After completing quantum mechanics as above, the difficulty in understanding the problem of quantum measurement disappears naturally. Implications of the findings are also discussed.
ASPECTS OF THE DEBATE The debate between Niels Bohr and Albert Einstein concerning the interpretation of quantum mechanics extended from the fifth Solvay Conference in 1927 until the end of Einstein's life. The most dramatic exchange occurred in 1935, when Einstein, in collaboration with B. Podolsky and N. Rosen, published a paper in Physical Review entitled “Can quantum-mechanical description of physical reality be considered complete?”, concluding with a negative answer, and Bohr replied in the same journal, with a paper of the same title but giving a positive answer. Their arguments were restated, in some respects with greater clarity, in the Library of Living Philosophers volume on Einstein in 1949. The disagreements between Bohr and Einstein concerned not only the physical question expressed in the common title of their papers, but also philosophical questions about physical reality and human knowledge. Much light was thrown upon the Bohr–Einstein debate by the theorem of J. S. Bell (1964) and the experiments which it inspired. Bell showed that any physical theory which applies to a pair of spatially separated systems (as considered in the thought experiment of Einstein, Podolsky, and Rosen) and satisfies a certain locality condition will, in certain circumstances, disagree statistically with quantum mechanics. Consequently, the supplementation of the quantum mechanical description envisaged by Einstein and his collaborators (usually referred to as a “hidden variables theory”) must either violate the locality condition or clash with quantum mechanical predictions.
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.
Quantum mechanics has become the rising trend in modern physics and has completely changed people’s views of physics. This essay delves into the once-existing problems underlying quantum mechanics such as the conflict between substantiality and completeness in quantum mechanics and the relationship between causality and observation and analyzes the solutions to the controversies. The Copenhagen Interpretation is widely considered the most orthodox explanation of quantum mechanics; therefore, this paper focuses on the Copenhagen Interpretation and examines how it delicately manages to explain quantum mechanics. It also examines its alternative theories, such as Einstein’s local hidden variable theory, and disproves them with Bell’s inequality and other reasonings. The essay aims to clarify and systematize the historical development of quantum mechanics, showing the current progress of quantum mechanics.
The EPR paper and Bohr's reply to it brought to an end the public debate between Einstein and Bohr. In the aftermath, Bohr's construal of quantum mechanics established itself as the basis of the orthodox interpretation – the ‘Copenhagen interpretation’ as it came to be called. The vast majority of physicists regarded Einstein's criticism as reactionary, and dismissed it with disdain. One of the main causes of this disdainful attitude was the general opinion that Einstein's criticism committed him to the existence of hidden states, and the existence of these, it was thought, had been conclusively ruled out by the work of von Neumann and others. What light does the subsequent work on the question of hidden states, and in particular the work of Bell, throw on the Bohr–Einstein dispute? Completeness and hidden states There are three distinct questions concerning hidden states. First, might there be such states, unbeknown to quantum mechanics? Second, can quantum mechanics, as it stands, take account of such states? Third, could some theory containing descriptions of such states reduplicate the predictions of quantum mechanics? Concerning the first of these questions, Einstein's view was that it is very likely that such states exist, and since quantum mechanics takes no account of them, it is incomplete and best regarded as a statistical theory analogous in some respects to classical statistical mechanics.