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Wavefunction Collapse Broadens Molecular Spectrum
Spectral lines in the optical spectra of atoms, molecules, and other quantum systems are characterized by a range of frequencies ω or a range of wavelengths λ=2πc/ω, where c is the speed of light. Such a frequency or wavelength range is called the width of the spectral lines (linewidth). It is influenced by many specific factors. Thermal motion of the molecules results in broadening of the lines as a result of the Doppler effect (thermal broadening) and by their collisions (pressure broadening). The electric fields of neighboring molecules lead to Stark broadening. The linewidth to be considered here is the so-called parametric broadening (PB) of spectral lines in the optical spectrum. PB can be considered the fundamental type of broadening of the electronic vibrational–rotational (rovibronic) transitions in a molecule, which is the direct manifestation of the basic concept of the collapse of a wavefunction that is postulated by the Copenhagen interpretation of quantum mechanics. Thus, that concept appears to be not only valid but is also useful for predicting physically observable phenomena.
  • 743
  • 11 Apr 2023
Topic Review
Wave-particle Duality Relation
The Wave–particle duality relation, often loosely referred to as the Englert–Greenberger–Yasin duality relation, or the Englert–Greenberger relation, relates the visibility, [math]\displaystyle{ V }[/math], of interference fringes with the definiteness, or distinguishability, [math]\displaystyle{ D }[/math], of the photons' paths in quantum optics. As an inequality: Although it is treated as a single relation, it actually involves two separate relations, which mathematically look very similar. The first relation, derived by Greenberger and Yasin in 1988, is expressed as [math]\displaystyle{ P^2+ V^2\le 1 \, }[/math]. It was later extended by Jaeger, Shimony, and Vaidman in 1995. This relation involves correctly guessing which of the two paths the particle would have taken, based on the initial preparation. Here [math]\displaystyle{ P }[/math] can be called the predictability. An year later Englert, in 1996, derived a related relation which dealt with experimentally acquiring knowledge of the two paths using an apparatus, as opposed to predicting the path based on initial preparation This relation is [math]\displaystyle{ D^2+ V^2\le 1 \, }[/math]. Here [math]\displaystyle{ D }[/math] is called the distinguishability. The significance of the relations is that they express quantitatively the complementarity of wave and particle viewpoints in double slit experiments. The complementarity principle in quantum mechanics, formulated by Niels Bohr, says that the wave and particle aspects of quantum objects cannot be observed at the same time. The wave–particle duality relations makes Bohr's statement more quantitative – an experiment can yield partial information about the wave and particle aspects of a photon simultaneously, but the more information a particular experiment gives about one, the less it will give about the other. The predictability [math]\displaystyle{ P }[/math] which expresses the degree of probability with which path of the particle can be correctly guessed, and the distinguishability [math]\displaystyle{ D }[/math] which is the degree to which one can experimentally acquire information about the path of the particle, are measures of the particle information, while the visibility of the fringes [math]\displaystyle{ V }[/math] is a measure of the wave information. The relations shows that they are inversely related, as one goes up, the other goes down.
  • 334
  • 27 Sep 2022
Biography
Valery Rubakov
Valery Anatolyevich Rubakov (Russian: Валерий Анатольевич Рубаков, born 16 February 1955 in Moscow, USSR) is a Russian theoretical physicist. His scientific interests include quantum field theory, elementary particle physics, and cosmology. He is affiliated with the Institute for Nuclear Research (INR) of the Russian Academy of Sciences in Moscow. Rubakov studied phys
  • 475
  • 15 Nov 2022
Topic Review
Vacuum State
In quantum field theory, the quantum vacuum state (also called the quantum vacuum or vacuum state) is the quantum state with the lowest possible energy. Generally, it contains no physical particles. Zero-point field is sometimes used as a synonym for the vacuum state of an individual quantized field. According to present-day understanding of what is called the vacuum state or the quantum vacuum, it is "by no means a simple empty space". According to quantum mechanics, the vacuum state is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence. The QED vacuum of quantum electrodynamics (or QED) was the first vacuum of quantum field theory to be developed. QED originated in the 1930s, and in the late 1940s and early 1950s it was reformulated by Feynman, Tomonaga and Schwinger, who jointly received the Nobel prize for this work in 1965. Today the electromagnetic interactions and the weak interactions are unified (at very high energies only) in the theory of the electroweak interaction. The Standard Model is a generalization of the QED work to include all the known elementary particles and their interactions (except gravity). Quantum chromodynamics (or QCD) is the portion of the Standard Model that deals with strong interactions, and QCD vacuum is the vacuum of quantum chromodynamics. It is the object of study in the Large Hadron Collider and the Relativistic Heavy Ion Collider, and is related to the so-called vacuum structure of strong interactions.
  • 3.1K
  • 17 Oct 2022
Topic Review
Universe & Anharmonic Oscillator & Singularity Avoidance Higgs
The functioning of our universe and atomic is based on the oscillation of the particle itself and asymmetrically between matter and antimatter. This mechanism is a classical an-harmonic oscillator and uses a linear oscillation of the particle, where the energy can be represented by the graph of a potential well. In this potential well the alternation of energies ocurs between the kinetic energy and potential energy. This an-harmonic oscillation of the particle thus occurs through a gravitational oscillator (see "hole through the Earth simple harmonic motion"), followed by a singularity avoidance. Indeed the important kinetics of the particle leads to a singularity avoidance to pass over the supermassive black hole to plot the Higgs field/potential. The alternation of the particle at very high frequency generates by the principle of mass-energy equivalence in vacuum (E=mc²) a mass flux expressed by the quantum fluctuation determined by a scalar energy density. This scalar density represents for example the dark matter and the residues of the latter in the quantum vacuum. However a vectorial interpretation of the particle is possible as soon as its oscillation through the oscillator is really minimized before becoming a mass-energy equivalence flux. That represent the elements related to Einstein's Stress Energy Tensor. Here is the one of interpretation of quantum mechanics in relation to relativistic physics. 
  • 2.3K
  • 23 Aug 2022
Topic Review Peer Reviewed
Undecidability and Quantum Mechanics
Recently, great attention has been devoted to the problem of the undecidability of specific questions in quantum mechanics. In this context, it has been shown that the problem of the existence of a spectral gap, i.e., energy difference between the ground state and the first excited state, is algorithmically undecidable. Using this result herein proves that the existence of a quantum phase transition, as inferred from specific microscopic approaches, is an undecidable problem, too. Indeed, some methods, usually adopted to study quantum phase transitions, rely on the existence of a spectral gap. Since there exists no algorithm to determine whether an arbitrary quantum model is gapped or gapless, and there exist models for which the presence or absence of a spectral gap is independent of the axioms of mathematics, it infers that the existence of quantum phase transitions is an undecidable problem. 
  • 1.0K
  • 18 Oct 2022
Topic Review
Two-Dimensional Quantum Billiards
Two-dimensional quantum billiards are one of the most important paradigms for exploring the connection between quantum and classical worlds. Researchers are mainly focused on nonintegrable and irregular shapes to understand the quantum characteristics of chaotic billiards. The emergence of the scarred modes relevant to unstable periodic orbits (POs) is one intriguing finding in nonintegrable quantum billiards. On the other hand, stable POs are abundant in integrable billiards. The quantum wavefunctions associated with stable POs have been shown to play a key role in ballistic transport. 
  • 288
  • 19 Oct 2023
Topic Review
Transition of State
In quantum mechanics, particularly Perturbation theory, a transition of state is a change from an initial quantum state to a final one.
  • 261
  • 08 Nov 2022
Topic Review Peer Reviewed
The Second Quantum Revolution: Unexplored Facts and Latest News
The Second Quantum Revolution refers to a contemporary wave of advancements and breakthroughs in the field of quantum physics that extends beyond the early developments of Quantum Mechanics that occurred in the 20th century. One crucial aspect of this revolution is the deeper exploration and practical application of quantum entanglement. Entanglement serves as a cornerstone in the ongoing revolution, contributing to quantum computing, communication, fundamental physics experiments, and advanced sensing technologies. Here, we present and discuss some of the recent applications of entanglement, exploring its philosophical implications and non-locality beyond Bell’s theorem, thereby critically examining the foundations of Quantum Mechanics. Additionally, we propose educational activities that introduce high school students to Quantum Mechanics by emphasizing entanglement as an essential concept to understand in order to become informed participants in the Second Quantum Revolution. Furthermore, we present the state-of-art developments of a largely unexplored and promising realization of real qubits, namely the molecular spin qubits. We review the available and suggested device architectures to host and use molecular spins. Moreover, we summarize the experimental findings on solid-state spin qubit devices based on magnetic molecules. Finally, we discuss how the Second Quantum Revolution might significantly transform law enforcement by offering specific examples and methodologies to address the evolving challenges in public safety and security.
  • 424
  • 02 Apr 2024
Topic Review
The Concept of “Quantum-Like”
The birth and spread of the prefix “quantum-” to disciplines other than physics, and the introduction of the term “quantum-like”, reflect the increasing dissatisfaction with the perceived limits and pitfalls of classic Western thought. Of course, the latter remains valuable; what is wrong is its dogmatic use and the claim of its exclusive capacity to comprehend the world. The development of quantum physics has been paralleled by the introduction of paraconsistent logics, such as fuzzy logic and dialetheism, a clear sign of the need for smoothing the inflexibility of Aristotelian logic. There is also a fil rouge (viz. an epistemological symmetry) linking the paradigm of quantum physics to ancient pre-Socratic and Eastern philosophies, suggesting the need for reappraising them in the process of reexamination of the classical thought. The increasing use of the term “quantum-like” calls for the defining and sharing of its meaning in order to properly adopt it and avoid possible misuse. 
  • 702
  • 14 Mar 2022
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