This paper mainly discusses the measurement in quantum mechanics. At first,it starts from the postulates of quantum mechanics and the meaning of measurement postulate is mainly analyzed. Secondly, the measurement problem which is one of the controversial problems of quantum mechanics is presented. Then the collapse theory and the no-collapse theory are illustrated respectively and the rationality of the two theories is stated by drawing a comparison between them. And then the discussion of simultaneous measurement is presented. Finally, representations of measurement in several virtual hardware models are briefly described and also the problems that measurement brings about are considered.
This paper mainly discusses the measurement in quantum mechanics. At first,it starts from the postulates of quantum mechanics and the meaning of measurement postulate is mainly analyzed. Secondly, the measurement problem which is one of the controversial problems of quantum mechanics is presented. Then the collapse theory and the no-collapse theory are illustrated respectively and the rationality of the two theories is stated by drawing a comparison between them. And then the discussion of simultaneous measurement is presented. Finally, representations of measurement in several virtual hardware models are briefly described and also the problems that measurement brings about are considered.
ABSTRACT This essay aims at reviewing one of the major difficulties affecting the standard formulation of quantum mechanics, that is, the well‐known measurement problem. As it will be explained, the latter originates as a consequence of the quantum theory's postulates. Referring to this, we analyze in particular the conceptual issues implied by the projection (or collapse) rule. After having presented the measurement problem, we then illustrate three possible solutions offered by major interpretations of/alternatives to quantum theory: Bohmian mechanics, Ghirardi–Rimini–Weber theories, and the many‐worlds interpretation. As the reader will see, these theoretical frameworks solve this issue by virtue of their unambiguous ontologies and consistent dynamical laws. Finally, a synopsis of the open debates and future perspectives concerning the measurement problem in relativistic contexts concludes the paper.
The theoretical description of measurement in quantum mechanics is one of the most controversial topics in physics. It is deeply entrenched in the interpretations of quantum mechanics and combines both physics and philosophy into the discussion. Often it is described as the measurement problem because of some issues associated with the theory of measurement introduced by John von Neumann in 1932, related to the fact that the Born projection postulate is not unitary and so is not described by the time-dependent Schrödinger equation. We discuss that theory later in this chapter, but we start from a simpler approach focused on what is actually being done in most single-quantum experiments. Along the way, we encounter a number of counterintuitive and subtle issues, before we explain why we refuse to tackle the measurement problem itself. Specific experiments that we discuss in detail include how we can measure individual quanta and how we can manipulate entanglement and perform delayed choice experiments, quantum beats, atom interferometry, and quantum non-demolition experiments in cavity QED.
The measurement problem of quantum theory has troubled the minds of physicists and philosophers for decades. This paper will discuss a relatively new attempt at resolving the issue, known as the mechanism of the “flea”, as put forward by Landsman and Reuvers in [13] and by Landsman in [12]. This paper first reviews the formalism of algebraic quantum theory. Chapter 3 then contains the greatest conceptual work, given by a novel understanding of the measurement problem. In this context, a small, asymmetric perturbation that arises from the environment is postulated, as described in chapter 4. This “flea” perturbation provides the symmetry breaking required for a classical state to emerge from a quantum system, thereby bringing us one step closer to a possible solution of the measurement problem. Chapter 5 hopes to offer an evaluation of the flea mechanism. These comments focus on the limitations of the models considered, as well as the nature of the flea perturbation. In particular, the challenges in attempting to recover the Born rule are discussed. This discussion is informed by the work of Van Heugten and Wolters in [22]. Finally, the conclusion contains some general reflections on the flea proposal, portraying it as the start of a new way of making the idea of a wave function collapse mathematically precise.
In this paper, we discuss the importance of measurement in quantum mechanics and the so-called measurement problem. Any quantum system can be described as a linear combination of eigenstates of an operator representing a physical quantity; this means that the system can be in a superposition of states that corresponds to different eigenvalues, i.e., different physical outcomes, each one incompatible with the others. The measurement process converts a state of superposition (not macroscopically defined) in a well-defined state. We show that, if we describe the measurement by the standard laws of quantum mechanics, the system would preserve its state of superposition even on a macroscopic scale. Since this is not the case, we assume that a measurement does not obey to standard quantum mechanics, but to a new set of laws that form a “quantum measurement theory”.
The main difficulty facing no-collapse theories of quantum mechanics in the Everettian tradition concerns the role of probability within a theory in which every possible outcome of a measurement actually occurs. The problem is two-fold: First, what do probability claims mean within such a theory? Second, what ensures that the probabilities attached to measurement outcomes match those of standard quantum mechanics? Deutsch has recently proposed a decision-theoretic solution to the second problem, according to which agents are rationally required to weight the outcomes of measurements according to the standard quantum-mechanical probability measure. I show that this argument admits counterexamples, and hence fails to establish the standard probability weighting as a rational requirement.
Quantum Information Theory (QIT) has emerged as one of the most influential fields in modern science, combining the principles of quantum mechanics with classical information theory. It forms the theoretical foundation of advanced technologies such as quantum computing, quantum communication, and quantum cryptography. Despite remarkable progress in these areas, the measurement problem remains a fundamental conceptual and practical challenge. Measurement in quantum mechanics plays a dual role: it enables information extraction while simultaneously disturbing the quantum system. This paper presents a detailed study of the measurement problem within the framework of quantum information theory. It examines the role of measurement in quantum state evolution, the effects of entanglement and decoherence, and the impact on information processing tasks. The paper also discusses existing theoretical approaches and highlights the importance of resolving measurement-related issues for the future development of quantum technologies.