Quantum indeterminacy and the eigenstate-eigenvalue link

Ulrich Mohrhoff

There are reasons to doubt that making sense of the wave function (other than as a probability algorithm) will help with the project of making sense of quantum mechanics. The consistency of the quantum-mechanical correlation laws with the existence of their correlata is demonstrated. The demonstration makes use of the fact (which is implied by the indeterminacy principle) that physical space is not partitioned "all the way down," and it requires that the eigenvalue-eigenstate link be replaced by a different interpretive principle, whose implications are explored.

Lars‐Göran Johansson

Moses Fayngold

A state of a single particle can be represented by a quantum blob in the corresponding phase space, or by a cell in its 2-D subspace. Its area is frequently stated to be no less than one half of the Plank constant, implying that such a cell is an indivisible quantum of the 2-D phase space. But this is generally not true, as is evident, for instance, from representation of some states in the basis of innately discrete observables like angular momentum. Here we consider some dispersed states involving the evanescent waves (EW) different from that in the total internal reflection. Such states are represented by a set of separated point-like cells, but with a large total indeterminacy. An idealized model has a discrete Wigner function forming an infinite periodic array of dots on the phase plane. The question about the total momentum indeterminacy in such state is discussed. We argue that the transverse momentum eigenstates corresponding to the considered EW-s cannot be singled out by any known measurement procedure, and the whole infinite set of the corresponding eigenvalues can contribute only a certain fraction to the observed momentum indeterminacy which remains finite.

X. P. Xu, Yusuke Ide, Norio Konno

It is generally believed that network structure has a profound impact on diverse dynamical processes taking place on networks. Tiny changes in the structure may cause completely different dynamics. In this paper, we study the impact of single extra link on the coherent dynamics modeled by continuous-time quantum walks. For this purpose, we consider the continuous-time quantum walk on the cycle with an additional link. We find that the additional link in cycle indeed causes a very different dynamical behavior compared to the dynamical behavior on the cycle. We analytically treat this problem, calculate the Laplacian spectrum, and approximate the eigenvalues and eigenstates using the Chebyshev polynomial technique and perturbation theory. It is found that the probability evolution exhibits a similar behavior like the cycle if the exciton starts far away from the two ends of the added link. We explain this phenomenon by the eigenstate of the largest eigenvalue. We prove symmetry of the long-time averaged probabilities using the exact determinant equation for the eigenvalues expressed by Chebyshev polynomials. In addition, there is a significant localization when the exciton starts at one of the two ends of the extra link; we show that the localized probability is determined by the largest eigenvalue and there is a significant lower bound for it even in the limit of infinite system. Finally, we study the problem of trapping and show the survival probability also displays significant localization for some special values of network parameters, and we determine the conditions for the emergence of such localization. All our findings suggest that the different dynamics caused by the extra link in cycle is mainly determined by the largest eigenvalue and its corresponding eigenstate. We hope the Laplacian spectral analysis in this work provides a deeper understanding for the dynamics of quantum walks on networks.

W. D. Heiss, A. A. Kotz�