What is usually called modern physics is based on two theories: relativity, which we have just nished discussing, and quantum mechanics (also called quantum theory). While some of the ideas of relativity, such as time dilation and length contraction, at rst seemed rather strange, we saw that they followed logically from the two postulates of relativity. We will see below that the ideas of quantum mechanics are also strange. Most physicists would agree that they are much stranger than relativity. In fact, we will see that there are no satisfactory explanations. To quote two Nobel Prize laureates, Murray Gell-Mann and Richard Feynman, “Nobody really understands quantum theory.” Despite this, it is one of the best-tested theories that we have. In some cases, the agreement between the theoretical prediction and experiment is better than 1 part in a million. There are many useful devices that are based on quantum mechanics. They include anything that uses microelectronics, such as a cell phone, DVD player, or computer, nuclear reactors, and medical imaging devices such as MRI and PET.
What is usually called modern physics is based on two theories: relativity, which we have just nished discussing, and quantum mechanics (also called quantum theory). While some of the ideas of relativity, such as time dilation and length contraction, at rst seemed rather strange, we saw that they followed logically from the two postulates of relativity. We will see below that the ideas of quantum mechanics are also strange. Most physicists would agree that they are much stranger than relativity. In fact, we will see that there are no satisfactory explanations. To quote two Nobel Prize laureates, Murray Gell-Mann and Richard Feynman, “Nobody really understands quantum theory.” Despite this, it is one of the best-tested theories that we have. In some cases, the agreement between the theoretical prediction and experiment is better than 1 part in a million. There are many useful devices that are based on quantum mechanics. They include anything that uses microelectronics, such as a cell phone, DVD player, or computer, nuclear reactors, and medical imaging devices such as MRI and PET.
Unlike special relativity, quantum mechanics was not the inspired product of one mind. It developed, in fits and starts, over a period of 25 years (1900–1925), and many cooks stirred the broth. Even now, a century later, quantum mechanics raises profound conceptual questions. Every competent physicist can “do” quantum mechanics, and the predictions it makes are in spectacularly good agreement with experimental results; there can be little doubt that quantum mechanics is “right.” On the other hand, as Richard Feynman once remarked, “nobody understands quantum mechanics.” I'll tell the story in two parts. First the history (how the essential pieces of the puzzle were assembled), and then the implications (what the finished picture has to say about our world). Photons Like relativity, quantum mechanics began with the study of light. In both cases, this historical association is misleading. Relativity, really, has nothing to do with light – to be sure, it involves that magic speed limit, c , and of course the most familiar thing that travels at speed c is light. So light is a convenient vehicle for introducing the subject. But it is perfectly possible to imagine a universe in which there is no such thing as light, and yet relativity might still be valid. Quantum mechanics, too, starts with light – in this case the “quantum” of light (the photon). But, as it turns out, this is just one rather specialized example of much more general principles – in fact, a rather bad example, because photons are by their nature relativistic (they travel at the speed of light), and it would be more natural to begin with the quantum mechanics of slow-moving objects, in analogy with Newtonian mechanics.
To date, the physical theory that most accurately describes the behavior of the atomic world is quantum mechanics. Since spectroscopy uses light to probe the atomic and molecular world, it should not be much of a surprise to learn that quantum mechanics is used to describe how spectroscopy works. Nobel Prize-winning physicist Richard Feynmann once said, "If you think you understand quantum mechanics, you don't understand quantum mechanics." This chapter won't bring you to a complete understanding of quantum mechanics, Feynmann's quote notwithstanding. But it will try to point out the important aspects, and hopefully it will at least leave the reader with the understanding that spectroscopy is quantum-mechanically based. Science's job is to try to understand the natural universe. To do this, scientists try to generate models to describe and predict the universe's behavior. (Not the behavior of the entire universe, but small selected parts of it.) If the model and the universe do not agree, there are two choices: change the model, or change the universe. Since all attempts at changing the universe have failed, our only choice is to change the model. Since the 1600s, scientific advance has accelerated at least in part because the proposed models of the universe have been increasingly more acceptable. Perhaps the first true âscientificâ investigation (by the modern definition) was Robert Boyle's investigation of gases in the 1660s. While there were some noteworthy incorrect or improper models developed (phlogiston and vitalism are two that come to mind immediately, but doubtless there are others), incorrect or improper models were ultimately replaced by more viable models. One such group of models was what we now call Newton's laws of motion. In just a few statements, verbal or mathematical, Newton's laws accurately describe the motion of matter. Further, these models withstood the test of multiple examinations, and are accepted as proper models of how matter behaves.
The difficulties of the old quantum theory were largely dispelled by the development of quantum mechanics in the 1920s. First Heisenberg (1925) developed the rather abstract matrix mechanics and soon after Schro¨dinger (1926; see also Eckart, 1926) developed the physically more appealing wave mechanics. Subsequently he showed them to be mathematically equivalent. The physicists were greatly relieved; now they had once again a mathematical formalism that enabled the results of experiments to be calculated. It was possible to move forward. It is certainly a very elegant and indeed beautiful formalism, and does enable the results of many physical measurements to be calculated with great accuracy. It is used daily by atomic and nuclear physicists; there is no other way to make calculations. From the earliest days there has been intense debate about the interpretation of quantum mechanics, and it shows no signs of being settled; if anything it is becoming more intense over the years. As Penrose has remarked, no one understands quantum mechanics. Feynman (1967; see also Sykes, 1994) also admitted that ‘nobody understands quantum mechanics’, and Einstein once remarked: ‘I have thought a hundred times as much about the quantum problems as I have about general relativity theory’ (Pais, 1994, p. 57). It should therefore be evident that the most that can be done here is to try to show where the real difficulties lie, and how the failure to recognize that quantum mechanics is an essentially statistical theory has led to a series of confusing quantum paradoxes. It is just these paradoxes that have often been used to support theological speculations. It is useful to ask what ‘understanding quantum mechanics’ actually means. Certainly it means being able to calculate the results of many measurements. The same applies to Newton’s theory of gravitation, which we understand in the sense that we can use it as a basis of calculation, although we do not really understand the gravitational force itself. Very often, especially in modern physics, the mathematical formalism does not give us the sort of intuitive physical feeling for what is going on that we often obtain from classical mechanics. Perhaps we can never achieve more than this for quantum mechanics. In classical mechanics we can assume that a property that is measured objectively exists prior to the interaction of the measuring apparatus with the observed system. Quantum mechanics, however, ‘is incompatible with the proposition that measurement discovers some unknown but pre-existing property’ (Peres, 1997, p. 14). There is an important distinction between mysteries and absurdities. We may be forced to live with mysteries, but there is no reason why we should put up with absurdities such as the wave-particle duality, tunnelling through potential barriers, acausal events and the collapse of the wave function. These are the quantum paradoxes that will be discussed later on. They arise within the Copenhagen interpretation of quantum mechanics and are solved by other interpretations. These alternative interpretations enable us to make conjectures about what is going on, even though we cannot understand it in detail. This is acceptable and a stimulus to further research. It is certainly difficult enough to understand quantum mechanics, but there is no need to try to visualize logical absurdities in the effort to do so. Quantum mechanics is a mathematical formalism that makes it possible to calculate the results of some experiments. Anything more than this, such as questions about the interpretation of what is measured and whether it tells us what is actually going on in the system being studied, belongs to philosophy. Thus we are concerned here with what is essentially a philosophical debate; if it were just a matter of physics the debate would have been settled long ago. One of the difficulties is that it invokes the results of experiments and uses the language of quantum mechanics. Inevitably this language uses philosophical terms and then it is easy to give the impression that the philosophical propositions are in some way entailed by the physical results. These in turn can influence theological thinking. In order to be quite clear which arguments are justified and which are not, it is essential to separate the three levels of discourse: physical, philosophical and theological. Our task is to relate these together, and this immediately raises the traditional problems of the philosophy of science, including the relation of experiment to theory, and of theory to explanation. We begin by discussing experiments, distinguishing between those that are real and those that are imaginary.
2025 is the year UNESCO selected to celebrate 100 years of this novel science, quantum mechanics, based on Heisenberg’s “uncertainty principle” discovery. However, quantum mechanics began with the discovery of quantum packets of energy emission formulated by the German physicist Max Planck, and it incorporated additional discoveries and principles from Albert Einstein, Niels Bohr, Heisenberg, Pauli, de Broglie, and many others in the early 1900s. Since then, many advancements and breakthroughs have been made. Such scientific contributions have influenced the culture and technology of humanity from the 20th century onwards, with the first quantum revolutions bringing innovations in technology and engineering, including the omnipresent light amplification by stimulated emission of radiation (Laser), magnetic resonance imaging (MRI), microprocessor manufacturing and design for computers and nuclear energy. Thus, at the beginning of the Second Quantum Revolution in the 21st century, amid a new wave of novel quantum technologies promising to create the 5th Industrial Revolution and transform humanity, a brief history of these marvellous sciences is condensed, connecting the wonders of the new quantum technogenesis that is being forged, linking its past with classical mechanics and also with novel relativistic mechanics. Understanding these developments highlights the significance of quantum technologies shaping our future and what lies ahead for us. This article explores technologies that are presently under research and development (R&D) in the quantum physics realm, including quantum computing, quantum cryptography, quantum sensing and metrology, and quantum simulation. It also discusses emerging careers in the quantum field and the unresolved mysteries that continue to challenge scientists. The discussion follows the ancient griot tradition of storytelling, a method that the distinguished physicist, great professor, and Nobel laureate Richard Feynman encouraged us to use to explain complex scientific ideas.
Quantum physics is the golden child of modern science. It is the basis of our understanding of atoms, radiation, and so much else, from elementary particles and basic forces to the behavior of materials. But for a century it has also been the problem child of science as it has been overwhelmed by intense disagreements between its inventors, strange paradoxes, and implications that seem like the stuff of fantasy. To understand the universe, quantum physics explores the behavior of the smallest particles in existence like quarks, electrons, and photons and which revealing a world that defies our everyday experiences and expectations. On the other hand, quantum mechanics (QM) is a fundamental theory in physics that describes the behavior of matter and energy at the atomic and subatomic levels, where classical physics fails to apply. However, the phenomena observed in QM can seem nothing short of miraculous. Physicists are trying to explain miracles of physics of universe meticulously which governed by precise scientific principles and mathematical equations. It is serious to modern technology, as its principles as well as wave-particle duality, superposition, and entanglement form the basis for electronics, computing, and medical technologies. The truth of QM in a scientific context refers to its exceptional ability to accurately describe and predict experimental results, not a philosophical ‘absolute truth’. Interestingly, the scientific elucidation of creation through quantum physics does not refute and contradict spiritual or religious narratives, rather augments our gratitude of the universe’s complexity and towards Almighty or Creator. The Bible’s or Quran’s account of creation provides a spiritual and philosophical outlook, accentuating purpose and intentionality. The precise explanations of particle behavior and cosmic formation in quantum physics, offers a balancing view grounded in empirical evidence. The purpose of this investigative study is to explore the scientific reality of QM and its purpose to depict the technical advancement for the development of modern civilization along with understand of universe in more logical way.
We have learned a lot about quantum mechanics already. We learned it is probabilistic and that it can have indeterminate behavior until measured. The Nobel Prize winner, Richard Feynman, summed this up the best with the following quote from his famous The Feynman Lectures in Physics: “We have implied that in our experimental arrangement (or even in the best possible one) it would be impossible to predict exactly what would happen. We can only predict the odds! This would mean, if it were true, that physics has given up on the problem of trying to predict exactly what will happen in a definite circumstance. Yes! Physics has given up. We do not know how to predict what would happen in a given circumstance, and we believe now that it is impossible-that the only thing that can be predicted is the probability of different events. It must be recognized that this is a retrenchment in our earlier ideal of understanding nature. It may be a backward step, but no one has seen a way to avoid it ⋯ So at the present time we must limit ourselves to computing probabilities. We say ‘at the present time,’ but we suspect very strongly that it is something that will be with us forever-that it is impossible to beat that puzzle-that this is the way nature really is.” Physicists are troubled that this is the way the real world is, but we have come to accept it so we can learn more about the mysteries of the real world. We examine advanced ideas surrounding the Stern-Gerlach experiment and its extensions including delayed-choice experiments, interaction-free experiments, and Bell experiments.