Studying the localisation-delocalisation property of confined quantum systems is crucial for advancements in quantum technology and information science. Here, we investigate the localisation-delocalisation property for a particle in a quantum well under the influence of an electric field by calculating position-momentum space standard deviations (Δx, Δp) and the Shannon entropies (Sx, Sp) as a function of the quantum well width (L) or the electric field strength (F). Our results suggest that when the width L or the strength F changes, both the standard deviations and the Shannon entropies can lead to consistent interpretations in measuring the localisation-delocalisation property of this system. Specifically, for a fixed magnitude of F, Δx and Sx increases with the width L, suggesting an extensive delocalisation, while they diminishes with increasing F for a given width of L, revealing the localisation property of this system. By comparing the behaviours of position-momentum uncertainty relation (ΔxΔp) and the Shannon entropy uncertainty relation (St = Sx + Sp), we find that the behaviour of ΔxΔp with L or F varies for different quantum state. In contrast, the variation of St with L or F is consistent across different quantum states. The underlying physical reasons for the effects of quantum well width and electric field strength on the uncertainty relations of this system are analysed from the differentiation perspective. This study provides deep insights into localisation-delocalisation property of a particle in a quantum well under external perturbations, and has significant applications in the field of quantum physics, condensed physics, semiconductor physics and material science.
Studying the localisation-delocalisation property of confined quantum systems is crucial for advancements in quantum technology and information science. Here, we investigate the localisation-delocalisation property for a particle in a quantum well under the influence of an electric field by calculating position-momentum space standard deviations (Δx, Δp) and the Shannon entropies (Sx, Sp) as a function of the quantum well width (L) or the electric field strength (F). Our results suggest that when the width L or the strength F changes, both the standard deviations and the Shannon entropies can lead to consistent interpretations in measuring the localisation-delocalisation property of this system. Specifically, for a fixed magnitude of F, Δx and Sx increases with the width L, suggesting an extensive delocalisation, while they diminishes with increasing F for a given width of L, revealing the localisation property of this system. By comparing the behaviours of position-momentum uncertainty relation (ΔxΔp) and the Shannon entropy uncertainty relation (St = Sx + Sp), we find that the behaviour of ΔxΔp with L or F varies for different quantum state. In contrast, the variation of St with L or F is consistent across different quantum states. The underlying physical reasons for the effects of quantum well width and electric field strength on the uncertainty relations of this system are analysed from the differentiation perspective. This study provides deep insights into localisation-delocalisation property of a particle in a quantum well under external perturbations, and has significant applications in the field of quantum physics, condensed physics, semiconductor physics and material science.
The study of quantum information entropy in confined quantum systems plays a pivotal role in quantum information science. In this work, we investigate the quantum information entropy of a particle in a quantum well under an external electric field by calculating the Rényi entropy (), Tsallis entropy () and the Onicescu information energy (). Our findings reveal that these entropic measures exhibit a strong dependence on the entropy order ( α ). Although both and demonstrate a decreasing trend with increasing α for any given quantum state, they differ significantly in their sensitivity to α variations, displaying distinct behaviors that provide unique insights into quantum uncertainty. For the Onicescu information energy (), a sharp transition around α = 1 appears. This characteristic could be significant for designing and analyzing quantum systems, particularly in enhancing their information processing capabilities. By further examining how these entropic measures vary with quantum well width and electric field strength, we gain a deeper understanding of the system's controllability. This empowers researchers to select optimal metrics for specific applications and improve the accuracy of quantum analyses. This study underscores the importance of entropy‐based analysis in quantum mechanics for advancing quantum control, information theory, and technology development.
With the development of quantum technology and information science, significant attention is focused on studying the quantum information properties in confined systems. In this work, we present a systematic investigation of quantum information measures – including position-momentum uncertainty (Δx,Δp), Shannon entropy (Sx, Sp), and Onicescu energy (Ox, Op) in a confined Robin harmonic oscillator (CRHO) with symmetric boundary conditions λL = λR = λ. It is interesting to find that the Heisenberg uncertainty relation ΔxΔp≥ℏ/2, which holds under the Dirichlet boundary condition (λ = 0), is violated for the ground state of the CRHO. In contrast, the entropic uncertainty relation (Sx + Sp ≥ 1 + lnπ) remains satisfied at any Robin length λ and quantum state, demonstrating its fundamental advantage and broader applicability in quantum systems. For a fixed Robin length, we observe that as the quantum well width increases within a finite range, the position-space Shannon entropy Sₓ increases, while the Onicescu energy Oₓ decreases. Despite their opposing tendencies, both Shannon entropy and Onicescu energy reflect the same physical insight regarding the localisation-delocalisation property for the CRHO system. In addition, the dependence of these information measures on the Robin length is discussed, and their physical implications are highlighted. This study demonstrates that boundary conditions play a critical role in quantum information metrics, thereby informing the design and optimisation of quantum devices such as quantum dots, nanoscale resonators and atom-based sensors.
In this study, we investigate the position and momentum Shannon entropy, denoted as Sx and Sp, respectively, in the context of the fractional Schrödinger equation (FSE) for a hyperbolic double well potential (HDWP). We explore various values of the fractional derivative represented by k in our analysis. Our findings reveal intriguing behavior concerning the localization properties of the position entropy density, ρs(x), and the momentum entropy density, ρs(p), for low-lying states. Specifically, as the fractional derivative k decreases, ρs(x) becomes more localized, whereas ρs(p) becomes more delocalized. Moreover, we observe that as the derivative k decreases, the position entropy Sx decreases, while the momentum entropy Sp increases. In particular, the sum of these entropies consistently increases with decreasing fractional derivative k. It is noteworthy that, despite the increase in position Shannon entropy Sx and the decrease in momentum Shannon entropy Sp with an increase in the depth u of the HDWP, the Beckner–Bialynicki-Birula–Mycielski (BBM) inequality relation remains satisfied. Furthermore, we examine the Fisher entropy and its dependence on the depth u of the HDWP and the fractional derivative k. Our results indicate that the Fisher entropy increases as the depth u of the HDWP is increased and the fractional derivative k is decreased.
Heisenberg’s uncertainty principle for position-momentum delta x delta p >= hbar/2 is considered as an important statement regarding quantum mechanics i.e. one cannot know both p and x exactly. Delta x and delta p stand out because in classical mechanics one has an eact p and x at each t. Mathematically, however, delta x and delta p are standard deviations which may also be calculated in classical statistical mechanics, for example with the Maxwell-Boltzmann distribution. In particular, if one considers the ground state of a simple harmonic oscillator, the quantum P(x) proportional to exp(-pp/a) and P(p) proportional to exp(-xxa) match the classical statistical probabilities P(x) and P(p) for a fixed value of T proportional to sqrt(k/m) where k is the spring constant. Thus for this special T, delta x delta p for a classical statistical mechanical gas is identical to delta x delta p for the ground state quantum oscillator. The probability is normalized the same way for both. The physics of the two situations, however, is completely different. Thus the Heisenberg uncertainty principle does not necessarily describe quantum mechanical behaviour alone. If one uses entropic uncertainty, i.e. Sp + Sx where S is Shannon’s entropy, once again one uses P(p)=a*(p)a(p) and P(x)=W*(x)W(x) where W(x)=wavefunction = Sum over p a(p)exp(ipx). In principle, one could also calculate such an entropy for a classical gas i.e. use P(x)P(p) in Shannon’s entropy. The result Sp+Sx does not imply one does not know about p if one knows x i.e. the usual quantum statement.
We review how external electric fields reshape the information content of spatially confined atoms, and we contrast the response to a uniform static field with that to a monochromatic, time-dependent laser field. The central quantities are the Shannon entropies in position and momentum space, Sr and Sp, and their sum ST = Sr +Sp, which obeys the BBM bound. Using the confined hydrogen atom (CHA) and the particle in a spherical box (PISB), its tight confinement limit, as reference systems, we first show that the field-free total entropy of the CHA depends non-monotonically on the confining radius whereas that of the PISB is strictly scale invariant. We then present Stark maps of the entropies for the ten lowest m = 0 levels at the confining radius of 6 a.u. The ground-state polarizability is reduced from the free-atom value 4.5 a.u. to 4.06 a.u. in the CHA but is 46.8 a.u. in the PISB, and the entropic response of the two systems differs correspondingly.
Analytical solutions of the Schrödinger equation for the one-dimensional quantum well with all possible permutations of the Dirichlet and Neumann boundary conditions (BCs) in perpendicular to the interfaces uniform electric field [Formula: see text] are used for the comparative investigation of their interaction and its influence on the properties of the system. Limiting cases of the weak and strong voltages allow an easy mathematical treatment and its clear physical explanation; in particular, for the small [Formula: see text], the perturbation theory derives for all geometries a linear dependence of the polarization on the field with the BC-dependent proportionality coefficient being positive (negative) for the ground (excited) states. Simple two-level approximation elementary explains the negative polarizations as a result of the field-induced destructive interference of the unperturbed modes and shows that in this case the admixture of only the neighboring states plays a dominant role. Different magnitudes of the polarization for different BCs in this regime are explained physically and confirmed numerically. Hellmann-Feynman theorem reveals a fundamental relation between the polarization and the speed of the energy change with the field. It is proved that zero-voltage position entropies [Formula: see text] are BC independent and for all states but the ground Neumann level (which has [Formula: see text]) are equal to [Formula: see text] while the momentum entropies [Formula: see text] depend on the edge requirements and the level. Varying electric field changes position and momentum entropies in the opposite directions such that the entropic uncertainty relation is satisfied. Other physical quantities such as the BC-dependent zero-energy and zero-polarization fields are also studied both numerically and analytically. Applications to different branches of physics, such as ocean fluid dynamics and atmospheric and metallic waveguide electrodynamics, are discussed.