The article deals with the origins and development, in the first quarter of the 20th century, of the fundamental ideas advanced by Planck and Einstein and by Bohr and de Broglie concerning the quantum of action, the quanta of energy and the quanta of light, the stationary states of atomic systems and jumplike transitions between them, the correspondence principle, and the particle-wave dualism. It is shown how the development of the quantum concepts have led to two approaches to the creation of quantum mechanics by Heisenberg, Born, and Dirac in algebraic form and by Schrodinger in analytic form. The main stages in the evolution of nonrelativistic quantum mechanics are described, namely the development of wave mechanics and matrix mechanics, the proofs of their equivalence, the physical interpretation of the wave function, the generalized formulation of quantum mechanics as a unified theory, and the discovery of the uncertainty relations. The most important trends in the development of quantum mechanics in the course of its evolution are considered. A complete bibliography of the main period of evolution of quantum mechanics (July 1925–March 1928), classified by topics and by time of publication, is included.
The article deals with the origins and development, in the first quarter of the 20th century, of the fundamental ideas advanced by Planck and Einstein and by Bohr and de Broglie concerning the quantum of action, the quanta of energy and the quanta of light, the stationary states of atomic systems and jumplike transitions between them, the correspondence principle, and the particle-wave dualism. It is shown how the development of the quantum concepts have led to two approaches to the creation of quantum mechanics by Heisenberg, Born, and Dirac in algebraic form and by Schrodinger in analytic form. The main stages in the evolution of nonrelativistic quantum mechanics are described, namely the development of wave mechanics and matrix mechanics, the proofs of their equivalence, the physical interpretation of the wave function, the generalized formulation of quantum mechanics as a unified theory, and the discovery of the uncertainty relations. The most important trends in the development of quantum mechanics in the course of its evolution are considered. A complete bibliography of the main period of evolution of quantum mechanics (July 1925–March 1928), classified by topics and by time of publication, is included.
This chapter starts with the historical development of quantum mechanics and explanations of key concepts behind fundamental discoveries such as Planck's hypothesis, the photoelectric effect, Bohr's atomic model, Compton scattering, the de Broglie hypothesis, the Pauli exclusion principle, the Schrödinger equation, Heisenberg quantum mechanics and the uncertainty principle, the Born interpretation of wave function, the Davisson and Germer experiment, and Dirac relativistic quantum mechanics, which made important contributions to the foundation of modern quantum mechanics. Concepts like the particle properties of radiation, the wave properties of matter, quantized energy and momentum, and the idea that one can no longer know exactly where a single particle like an electron is at any instant of time are brought out clearly through this chapter. A list of important quantum mechanical parameters along with solved examples and unsolved exercises on the key concepts are included towards the end.
In the 20th century, two new terms were added to the scientific lexicon: relativistic mechanics and quantum mechanics. The challenge to the concept of the absoluteness of space and time started at the end of the 19th century and gave birth to Einstein's special relativity theory in 1905. This unified space and time to a single entity, space–time, and we have been introduced to many new concepts such as time dilation, space contraction, mass–energy relation, and the space–time continuum in relativity theory. We have also learned that the highest possible velocity in this universe is that of light and that nothing in the universe can move faster than light. Einstein's general theory of relativity took into consideration gravitation and established the chronogeometric concept of gravity. Quantum mechanics developed by Bohr, de Broglie, Heisenberg, Schrödinger, and others gave us knowledge in the atomic and subatomic domain and led to the wave–particle duality of de Broglie, the uncertainty principle of Heisenberg, the wave mechanics of Schrödinger, and so forth. We have learned that three distinct chords are at the heart of quantum mechanics—granularity, relational, and indeterminism. Although quantum mechanics is a weird subject, as we will discuss, the modern physics is totally based on it.
This invaluable book takes the reader from Planck's discovery of the quantum in 1900 to the most recent interpretations and applications of nonrelativistic quantum mechanics. The introduction of the quantum idea leads off the prehistory of quantum mechanics, featuring Planck, Einstein, Bohr, Compton, and de Broglie's immortal contributions. Their original discovery papers are featured with explanatory notes and developments in Part 1. The invention of matrix mechanics and quantum mechanics by Heisenberg, Born, Jordan, Dirac, and Schrödinger is presented next, in Part 2. Following that, in Part 3, are the Einstein–Bohr debates on the interpretation of quantum mechanics culminating in Bell's inequality and Aspect's experiment demonstrating the actuality of the long range quantum correlations to which Einstein, Podolsky, and Rosen took great exception. Resolutions of quantum paradoxes and the current state of such debates are summarized. Part 4 presents a selection of the most dramatic modern developments, both theoretical and experimental. These include Feynman path integrals, the modern interpretation based on decoherence, quantum optics experiments leading to teleportation, DeWitt's wave function of the universe, and a brief introduction to the end-of-the-millennium prospects of quantum computation. A concluding chapter presents the authors' conjectures for the next 100 years of the quantum. This book is ideally suited to anyone with a junior level background in modern physics and quantum mechanics, and a cultural interest in the original sources of the greatest ideas of the greatest founders of this subject as derived from their first discovery papers. These papers have led, in giant strides across the whole of the twentieth century, to the revolutionary experimental advances of the last decade. The book makes accessible - physically and intellectually - both the deepest roots and the highest branches of nonrelativistic quantum physics
Abstract Following the path by which humanity learned quantum mechanics can lead to an improved understanding of the theory and the origins of its perceived limitations. Our goal is to retrace the development by investigating primary sources, including original published papers and letters, with attention to their timing and influence. Quantum mechanics began in 1900 with the introduction of Planck’s constant, which lead to the “old” quantum theory and Bohr’s model of the atom. With the introduction of matter waves in 1924, a second more intense period began. By 1928 the complete fundamental structure of quantum mechanics was established with the introduction of the Schrödinger equation, the proof of its equivalence to Heisenberg’s matrix mechanics, and the introduction of the relativistic Dirac equation. The theory retains the same essential form today, fueling the technological revolution that began in the last century. We culminate with an introduction to quantum information and computing. This completely new physical scientific paradigm was developed largely in Germany during a period of enormous social, economic, and political upheaval—in a hostile intellectual environment—that parallels the overturning of classical physics. It is striking that all the problems debated today were immediately recognized by the founders of the theory and instructive to see how they dealt with the various issues. We emphasize the centrality of the often neglected second quantization form of the theory for questions of interpretation and give a detailed examination of von Neumann’s widely misunderstood hidden variable theorem.
The purpose of the article is to show that quantum mechanics is a synthesis of the old classical concepts and the new non-classical concepts (physics and mathematics). To illustrate the relationship of continuity between classical physics and quantum mechanics, the materials of Planck, Broglie, Schrodinger, Bohr and Dirac are considered. The author begins with a comparative study of the fundamental principles of classical and quantum physics, and concludes that, despite their opposition and irreducibility, scientists tried to adopt the principles of classical physics for constructing quantum mechanics. Survey of Planck's papers showed that Planck's formula for the blackbody spectrum containing the quantum of action is obtained as a synthesis of classical concepts and quantum concepts. Survey of Broglie's papers showed that the quantum-mechanical concept of Broglie emerged as a synthesis of the provisions of the classical (variation principles) and quantum physics (Planck's constant). Survey of Schrodinger's papers showed great generality of quantum theory in comparison with classical mechanics. Survey of Bohr's papers showed that Bohr was able to prove the basic concepts of quantum physics with the help of methodological principles. Survey of Dirac's papers showed that Dirac discovered the equivalence of Schrodinger's and Heisenberg's theories, showed that they go back to the same physical and algebraic principles, and that they can be formulated as variants of the quantum-mechanical system. The author considers the methodological features of quantum mechanics and fixes a number of methodological principles by which quantum mechanics is significantly different from classical physics. The category of quantum mechanics, on which an attempt to reconstruct the physical picture of the world based on quantum theory, is briefly discussed. On the basis of this reconstruction, there are the world picture broad categories: mass-field and space-time. The categories are related by the formula: wave-like particle moves in the classical space-time background. The first association the particles and interactions is from quantum mechanics, the second space and time from the special theory of relativity. In conclusion, a list of basic relations of quantum mechanics with classical physics is made. The development of quantum ideas resulted from direct influence of classical physics, so the main heuristic techniques to construct quantum theory are two ideas, namely, the idea of continuity and the idea of conformity which Bohr's methodological principles express. At the same time, quantum theory requires the use of classical concepts for support and verification. This is due to the restrictions imposed by the experimental technique. Thus, the author claims that quantum mechanics is a synthesis of the old classical concepts and the new non-classical concepts (physics and mathematics).
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.