Quantum First-Passage Time: Exact Solutions for a Class of Tight-Binding Hamiltonian Systems

TL;DR

This paper extends the classical first-passage time approach to quantum systems, providing exact analytical solutions for a class of tight-binding Hamiltonians, revealing finite quantum passage times with potential applications in electron transport.

Contribution

It introduces an analytical method for quantum first-passage time calculation in specific Hamiltonian systems, highlighting unique finite-time properties distinct from classical diffusion.

Findings

Quantum first-passage time probability density remains positive and normalized.

The quantum passage time domain is finite, unlike classical diffusive cases.

Derived solutions are relevant to electron transport in biomolecular and nanostructural systems.

Abstract

The Schr\"odinger integral-equation approach for calculating the classical first-passage time (C-fpt) probability density is extended to the case of quantum first-passage time (Q-fpt). Using this extension, we have calculated analytically the Q-fpt probability density for a class of few-site/state tight-binding Hamiltonian systems, e.g., a qubit, as well as for an infinite 1D lattice. The defining feature of such a quantum system is that the passage across the boundary between a subspace (omega) and its complement (omega-bar) is through a unique pair of "door-way" sites such that the first departure from (arrival at) omega corresponds to the first arrival at (departure from) omega-bar. The Q-fpt probability density so derived remains positive over the time interval in which it also normalizes to unity. These conditions of positivity and normalization define the physical time domain for the Q-fpt problem. This time domain is found to remain finite for the few-site/state Hamiltonian systems considered here, which is quite unlike the case for the diffusive C-fpt problems. The door-way sites and the associated Q-fpt probability density derived here should be relevant to inter-biomolecular/nanostructural electron transport phenomena.