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Physica Scripta

Ramsauer-Townsend effect in Shannon and Fisher quantum information entropy, and the uncertainty principle in collision dynamics

Santanu Mondal, R. Cabrera‐Trujillo

Published Jan 15, 2026• 0 citations
Publisher

Abstract

Abstract In quantum physics, the scattering of a free particle by an impurity leads to the Ramsauer-Townsend effect, characterized by resonances in the cross section for transmission and reflection of the incident particle. In this work, we analyze this problem within the context of quantum information theory. In particular, we study the Shannon and Fisher entropy, as well as the Heisenberg uncertainty relations, to analyze the fragmentation of a wave packet in collision dynamics. As a primary contribution of this work, we note that these properties are directly related to each other through the same reflection and transmission coefficients as those of the Ramsauer-Townsend effect. Furthermore, we observe that the Heisenberg uncertainty principle satisfies the minimum value, i.e. ℏ /2, for the transmitted wave packet at resonance transmission and a maximum at higher fragmentation of the wave packet. We obtain that at resonance transmission, the reflected contribution to the uncertainty principle is zero with no violation of the Heisenberg principle. This leads, consequently, to the violation of it by the reflected wave packet, as there is no reflection. Moreover, the Shannon and Fisher quantum information entropy is found to be directly connected to Heisenberg’s uncertainty principle for a dynamical system. Finally, we establish that these effects require the proper description of the time-dependent spreading of the wave packet to account for the proper dynamics.

DOI
10.1088/1402-4896/ae391b

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Abstract In quantum physics, the scattering of a free particle by an impurity leads to the Ramsauer-Townsend effect, characterized by resonances in the cross section for transmission and reflection of the incident particle. In this work, we analyze this problem within the context of quantum information theory. In particular, we study the Shannon and Fisher entropy, as well as the Heisenberg uncertainty relations, to analyze the fragmentation of a wave packet in collision dynamics. As a primary contribution of this work, we note that these properties are directly related to each other through the same reflection and transmission coefficients as those of the Ramsauer-Townsend effect. Furthermore, we observe that the Heisenberg uncertainty principle satisfies the minimum value, i.e. ℏ /2, for the transmitted wave packet at resonance transmission and a maximum at higher fragmentation of the wave packet. We obtain that at resonance transmission, the reflected contribution to the uncertainty principle is zero with no violation of the Heisenberg principle. This leads, consequently, to the violation of it by the reflected wave packet, as there is no reflection. Moreover, the Shannon and Fisher quantum information entropy is found to be directly connected to Heisenberg’s uncertainty principle for a dynamical system. Finally, we establish that these effects require the proper description of the time-dependent spreading of the wave packet to account for the proper dynamics.
The article intertwines the study of wave packet dynamics with information-theoretic measurements in one dimensional (D =1) system. A localized wave packet at time t=0 has been considered here and its change at later instant of time t is calculated for the position space wave function. The momentum space wave function is obtained by taking the Fourier transform of the position space wave function at time t= 0 . These wave functions are then employed to construct the wave packet's respective probability densities in position and momentum space, and later have been used to compute the corresponding position and momentum space Shannon (S) and Fisher information (I) entropies. It has been observed that although the Shannon and Fisher information entropies explicitly depend on the standard deviation, neither the Shannon entropy sum nor the product of Fisher information entropies is. Moreover, for D dimensional systems, the computed values of the Shannon and Fisher entropies are found to satisfy the lower bounds of the Bialynicki-Birula and Myceilski (BBM) inequality relation and the Stam-Cramer-Rao inequalities better known as the Fisher based uncertainty relation. Thus, our theoretical study explores the validation of information-theoretic measurements for wave packet dynamics using the basic formulations of information theory.
We analyze the functioning of Gibbs-type entropy functionals in the time domain, with emphasis on Shannon and Kullback-Leibler entropies of time-dependent continuous probability distributions. The Shannon entropy validity is extended to probability distributions inferred from L2(Rn) quantum wave packets. In contrast to the von Neumann entropy which simply vanishes on pure states, the differential entropy quantifies the degree of probability (de)localization and its time development. The associated dynamics of the Fisher information functional quantifies nontrivial power transfer processes in the mean, both in dissipative and quantum mechanical cases.
The Heisenberg uncertainty principle is one of the characteristics of quantum mechanics. With the vigorous development of quantum information theory, uncertain relations have gradually played an important role in it. In particular, in order to solved the shortcomings of the concept in the initial formulation of the uncertainty principle, we brought entropy into the uncertainty relation, after that, the entropic uncertainty relation has exploited the advantages to the full in various applications. As we all know the entropic uncertainty relation has became the core element of the security analysis of almost all quantum cryptographic protocols. This review mainly introduces development history and latest progress of uncertain relations. After Heisenberg's argument that incompatible measurement results are impossible to predict, many scholars, inspired by this viewpoint, have made further relevant investigations. They combined the quantum correlation between the observable object and its environment, and carried out various generalizations of the uncertainty relation to obtain more general formulas. In addition, it also focuses on the entropy uncertainty relationship and quantum-memory-assisted entropic uncertainty relation, and the dynamic characteristics of uncertainty in some physical systems. Finally, various applications of the entropy uncertainty relationship in the field of quantum information are discussed, from randomnesss to wave-particle duality to quantum key distribution.
Uncertainty principle, which was first introduced by Werner Heisenberg in 1927, forms a fundamental component of quantum mechanics. A graceful aspect of quantum mechanics is that the uncertainty relations between incompatible observables allow for succinct quan- titative formulations of this revolutionary idea: it is impossible to simultaneously measure two complementary variables of a particle in precision. In particular, information theory offers two basic ways to express the Heisenberg’s principle: variance-based uncertainty relations and entropic uncertainty relations. We first investigate the uncertainty relations based on the sum of variances and derive a family of weighted uncertainty relations to provide an optimal lower bound for all situations. Our work indicates that it seems unreasonable to assume a priori that incompatible observables have equal contribution to the variance-based sum form uncertainty relations. We also study the role of mutually exclusive physical states in the recent work and generalize the variance-based uncertainty relations to mutually exclusive uncertainty relations. Next, we develop a new kind of entanglement detection criteria within the framework of marjorization theory and its matrix representation. By virtue of majorization uncertainty bounds, we are able to construct the entanglement criteria which have advantage over the scalar detect- ing algorithms as they are often stronger and tighter. Furthermore, we explore various expression of entropic uncertainty relations, including sum of Shannon entropies, majorization uncer- tainty relations and uncertainty relations in presence of quantum memory. For entropic uncertainty relations without quantum side information, we provide several tighter bounds for multi-measurements, with some of them also valid for Rényi and Tsallis entropies besides the Shannon entropy. We employ majorization theory and actions of the symmetric group to obtain an admixture bound for entropic uncertainty relations with multi-measurements. Comparisons among existing bounds for multi-measurements are also given. However,classical entropic uncertainty relations assume there has only classical side information. For modern uncertainty relations, those who allowed for non-trivial amount of quantum side information, their bounds have been strengthened by our recent result for both two and multi- measurements. Finally, we propose an approach which can extend all uncertainty relations on Shannon entropies to allow for quantum side information and discuss the applications of our entropic framework. Combined with our uniform entanglement frames, it is possible to detect entanglement via entropic uncertainty relations even if there is no quantum side in- formation. With the rising of quantum information theory, uncertainty relations have been established as important tools for a wide range of applications, such as quantum cryptography, quantum key distribution, entanglement detection, quantum metrology, quantum speed limit and so on. It is thus necessary to focus on the study of uncertainty relations.
1: The Birth of Quantum Theory. 1.1: The radiation of an ideal black body. 1.2: Line spectra and Bohr's model of the atom. 1.3: The quantum conditions of Bohr-Sommerfield. 1.4: Waves of matters. Comments. Problems. 2: Classical Physics - Quantum Physics. 2.1: The difficulties of classical theory. 2.2: The successes of quantum theory. 2.3: Problems with interpretation of quantum theory. 2.4: Quantum theory (1930. Problems. II: Schrodinger's Equation and the Interpretation of its Solutions. 3: Schrodinger's Equation. 3.1: The Schrodinger equation with time. 3.2: The time-dependent Schrodinger equation. Comments. Problems. 4: The Probabilistic Interpretation of the Wavefunction. Comments. Problems. 5: The Motion of a Free Particle in Wave Mechanics. 5.1: The spreading of wave packets. 5.2: The initial problem for Schrodinger's free particle equation. 5.3: The Gaussian wave packet. Comments. Problems. 6: The Momentum of a Particle and the Fourier Transformation of the Wavefunction. Comments. Problems. 7: Description of Experiments in Wave Mechanics and the Heinsberg Uncertainty Principle. 7.1: Heisenberg's uncertainty principle. 7.2: The entropic uncertainty principle. Comments. Problems. 8: A Charged Particle in an Electromagnetic Field. Comments. Problems. 9: The Hydrodynamic Formulation of Wave Mechanics. 9.1: The motion of the probability fluid in an electromagnetic field. Comments. Problems. 10: The Spin of the Elctron and Pauli's Equation. 10.1: The magnetic moment vector. 10.2: Pauli's equation. 10.3: The Stern-Gerlach experiments. Comments. Problems. 11: The Hydrodynamic Picture of Wave Mechanics of a Particle with Spin. Comments. Problems. 12: Ehrenfest's Equations. 12.1: A particle with spin in the electromagnetic field. Problems. 13: Descriptiopn of Particle Motion in Phase Space -- Wigner's Function. Comments. Problems. 14: Mixed States. 14.1: An unpolarized beam as a mixed state. Comments. Problems. III: Solutions of Schrodinger's Equation. 15: Classification of Solutions to Schrodinger's Equation. 15.1: Scattering states. 15.2: The completeness of the set of bound and scattering state wavefunctions. 15.3: Orthogonality of the wavefunctions. 15.4: Development of the system in time. 15.5: Bound and scattered states. Problems. 16: Bound States and Energy. 16.1: The three-dimensional spherically symmetric potential well. Comments. Problems. 17: Scattering States and Collision Cross-sections. 17.1: One-dimensional scattering. 17.2: The method of integral equations. 17.3: Three-dimensional scattering. 17.4: The scattering amplitude. 17.5: The S matrix. 17.6: Collision cross-section. 17.7: The optical theorem. Comments. Problems. 18: Partial Waves and Wave Effects in Scattering. 18.1: Phase shifts. 18.2: The spherical potential hump. 18.3: The Ramsauer-Townsend effect. 18.4: The extinction paradox. Comments. Problems. 19: Resonance States. Problems. 20: The Coulomb Potential. 20.1: Bound states. 20.2: Scattering states. Comments. Problems. 21
The notion of Shannon entropy is crucial for the theory of classical information. In quantum information theory, an analogous key role is played by the von Neumann entropy: quantum information processing is closely related to entropy dynamics. This reveals a direct link with the theory of quantum chaotic systems, which can be characterized by a positive entropy production. Furthermore, noise, which inevitably affects any quantum system, can be modeled by a random quantum operation or by coupling to an environment in a generic chaotic state. In this contribution, we emphasize the universality of quantum chaotic dynamics and discuss its implications for quantum information processing.