Abstract The concept of the Quantum Ratio was born out of the efforts to find a simple but universal criterion if the center of mass (CM) of an isolated (microscopic or macroscopic) body behaves quantum mechanically or classically, and under which conditions. It is defined as the ratio between the quantum fluctuation range, which is the spatial extension of the pure-state CM wave function, and the linear size of the body (the space support of the internal, bound-state wave function). The two cases where the ratio is smaller than unity or much larger than unity, roughly correspond to the body’s CM behaving classically or quantum mechanically, respectively. An important notion following from the introduction of quantum ratio is that the elementary particles (thus the electron and the photon) are quantum mechanical. This is so even when the environment-induced decoherence turns them into a mixed state. Decoherence (mixed state) and classical state should not be identified. This simple observation is further elaborated, by analyzing some atomic or molecular processes. It may have far-reaching implications on the way quantum mechanics works, e.g., in biological systems.
Abstract The concept of the Quantum Ratio was born out of the efforts to find a simple but universal criterion if the center of mass (CM) of an isolated (microscopic or macroscopic) body behaves quantum mechanically or classically, and under which conditions. It is defined as the ratio between the quantum fluctuation range, which is the spatial extension of the pure-state CM wave function, and the linear size of the body (the space support of the internal, bound-state wave function). The two cases where the ratio is smaller than unity or much larger than unity, roughly correspond to the body’s CM behaving classically or quantum mechanically, respectively. An important notion following from the introduction of quantum ratio is that the elementary particles (thus the electron and the photon) are quantum mechanical. This is so even when the environment-induced decoherence turns them into a mixed state. Decoherence (mixed state) and classical state should not be identified. This simple observation is further elaborated, by analyzing some atomic or molecular processes. It may have far-reaching implications on the way quantum mechanics works, e.g., in biological systems.
The concept of the Quantum Ratio was born out of the efforts to find a simple but universal criterion if the center of mass (CM) of an isolated (microscopic or macroscopic) body behaves quantum mechanically or classically, and under which conditions. It is defined as the ratio between the quantum fluctuation range, which is the spatial extension of the pure-state CM wave function, and the linear size of the body (the space support of the internal, bound-state wave function). The two cases where the ratio is smaller than unity or much larger than unity, roughly correspond to the body's CM behaving classically or quantum mechanically, respectively. An important notion following from the introduction of quantum ratio is that the elementary particles (thus the electron and the photon) are quantum mechanical. This is so even when the environment-induced decoherence turns them into a mixed state. Decoherence (mixed state) and classical state should not be identified. This simple observation is further elaborated, by analyzing some atomic or molecular processes. It may have far-reaching implications on the way quantum mechanics works, e.g., in biological systems.
The concept of quantum ratio has emerged from recent efforts to understand how Newton’s equations appear for the center of mass (CM) of an isolated macroscopic body at finite body temperatures as a first approximation of quantum mechanical equations. It is defined as Q≡Rq/L0, where the quantum fluctuation range Rq is the spatial extension of the pure-state CM wave function, whereas L0 stands for the body’s linear size (the space support of the internal bound-state wave function). The two cases Rq/L0≲1 and Rq/L0≫1 roughly correspond to the body’s CM behaving classically or quantum mechanically, respectively. In the present note, we elaborate on this concept and illustrate it through several examples. An important notion following from introduction of the quantum ratio is that the elementary particles (thus, the electron and the photon) are quantum mechanical even when environment-induced decoherence places them into a mixed state. Thus, decoherence and classical state should not be identified. This simple observation, further illustrated by consideration of a few atomic and molecular processes, may have significant implications for the way that quantum mechanics works in biological systems.
Newton’s force law [Formula: see text] is derived from the Schrödinger equation for isolated macroscopic bodies, composite states of e.g. [Formula: see text] atoms and molecules, at finite body temperatures. We first review three aspects of quantum mechanics (QM) in this context: (i) Heisenberg’s uncertainty relations for their center of mass (CM), (ii) the diffusion of the CM wave packet, and (iii) a finite body temperature which implies a metastable (mixed-) state of the body: photon emissions and self-decoherence. They explain the origin of the classical trajectory for a macroscopic body. The ratio between the range [Formula: see text] over which the quantum fluctuations of its CM are effective, and the body’s (linear) size [Formula: see text], [Formula: see text] or [Formula: see text], tells whether the body’s CM behaves classically or quantum mechanically, respectively. In the first case, Newton’s force law for its CM follows from the Ehrenfest theorem. We illustrate this for weak gravitational forces, a harmonic-oscillator potential, and for constant external electromagnetic fields slowly varying in space. The derivation of the canonical Hamilton equations for many-body systems is also discussed. Effects due to the body’s finite size such as the gravitational tidal forces appear in perturbation theory. Our work is consistent with the well-known idea that the emergence of classical physics in QM is due to the environment-induced decoherence, but complements and completes it, by clarifying the conditions under which Newton’s equations follow from QM, and by deriving them explicitly.
Aiming at the quantum mechanics wave function description probability feature, statistical interpretation, randomicity, uncertainty, nonlocality and agnosticism etc fundamental principles and concepts, based on the mass-space interaction, mass-space space-time view, microscopic mass-energy systems correlating with space-time model etc principles and theories, and the quantum entanglement particle experiments etc facts, present the matter-ordering-energy conservation laws and the Dong Pei innovating group interpretation of quantum mechanics. Simultaneously indicate: In the universe there exists the ordering- and disordering-energy matter, together known as matter. Existing the absolute space and absolute time. The absolute space-time is continuous. Matter and the absolute space-time together create and compose the objective world. The objective world is a harmonious and unified whole. Physical laws are completely unified. The objective world and matter are all finite. Matter exists, evolves and moves in the absolute space-time. Interactions are the most essential and most root basic attribute of matter. The interaction among matter is the mass-space interaction. The mass-space interaction is continuous and stable, is not random and intermittent. Macroscopic and microscopic regions all observe the identical physical laws. Elementary particles and they compose the microscopic mass-energy systems are all the ordering-energy matter, their mass-energy space-time is a interdependent whole, their feature, state, structure and motion laws are all entirely determined by the mass-space interaction, correspond with the determinism and causality, the motion state and feature, motion orbitals, position and speed of particles in the absolute space-time are all absolutely determined and could be measured exactly, their quantum states could be approximately described by the wave function of quantum mechanics. The wave functions are the simplified mathematical function approximate expression of quantum system states of adopted interaction, can be used to calculate the correlative physical quantities. The wave functions could approximately describe the state of the mass-energy space-time whole of a microscopic mass-energy system with the mass-space interaction acting and continuously moving. An eigenstate just is the state making the system energy minimum and in rather stable existence. Scientific theories are the abstract simplified approximate expression for the essential of natural phenomena. Physical theory is the abstract simplified approximate representation for the matter structure and its motion laws. Whereas the mathematical formulation then is the further simplified approximate representation for physical contents. All of theories, include quantum mechanics and relativity, only when the assumed approximate condition is satisfied, just are the applied correct scientific theory, could describe the objective world good enough but not exactly. Develop scientific theory, correctly cognize and reasonably interpret the objective world, without the end.
The behavior of classical macroscopic particles – from baseballs to planets – is governed by Newtonian mechanics as we have described in the first chapters of this book. The behavior of very small particles, on the other hand, is governed by an entirely different collection of equations and rules that go under the name of “quantum mechanics” and these particles are referred to as quantum particles. These rules have analogies to classical mechanics, but are fundamentally different and somewhat mysterious as we discussed in Chapter 8. The fundamental principles of quantum mechanics cannot be proven to be correct. They were developed based on the results of experimental observation, by analogy with classical mechanics, and through the consideration of logical implications of the formalisms used. There is no way to derive the fundamental elements of quantum mechanics, any more than one could predict from first principles that Newtonian forces should add as vectors. On the other hand, quantum mechanics is among the most rigorously tested theories in science, and the predictions of quantum mechanics have, so far, always been in agreement with experiment. In this chapter, we will present quantum mechanics as a series of postulates and examine their implications in application to simple one-dimensional systems. In the next chapter we will examine quantum effects in real systems including atoms, molecules, crystals, and artificially engineered nano-structures. Postulates of quantum mechanics QM Postulate 1: A quantum particle is described by a wave function Ψ( x , y , z , t ) which is a function of spatial coordinates and time. All physically determinable quantities can be derived from the wave function Ψ( x , y , z , t ) ; quantities which cannot be found from the wave function are not physically meaningful. Note that some things that one could ask about a quantum particle, for example the exact position and simultaneous exact momentum of a particle, are not derivable from the wave function and are therefore considered indeterminate (or uncertain ). These are things which cannot ever be known about a particle, and, as such, they are meaningless to contemplate.
This chapter is a refresher on the fundamental concepts of quantum mechanics. One essential difference between classical and quantum mechanics is that in classical mechanics, we are used to deterministic and precise laws stemming from the fact that the act of measurement can be ignored. Indeed, for all practical purposes, the interaction with the macroscopic system to be measured can be rendered negligibly small. However, at very small scales, the situation changes radically. The assumption that the measurement is ignorable is not true for micro-objects. In order to perform a measurement, we must interact with the system we are measuring. We discovered experimentally that nature has an objective scale, encoded by Planck's constant, that limits our ability to perform perturbation-free measurements. All we can do is perform many measurements on identically prepared systems, which would allow us to determine the probability of a given outcome. Micro-objects behave non-intuitively, described by new laws, those of quantum mechanics. In this chapter, we will briefly cover the postulates of quantum mechanics and introduce the Schrodinger and Heisenberg pictures of quantum mechanics.