Closed-form expressions for the probability distribution of quantum walk on a line

TL;DR

This paper derives exact mathematical formulas for the probability distribution of quantum walks on a line, considering general coin operators and initial states, enhancing analytical understanding of quantum walk dynamics.

Contribution

It introduces a comprehensive method to obtain closed-form expressions for quantum walk distributions with general coins and initial states, including mixed states, using Fibonacci-Horner basis.

Findings

Validated formulas by matching with simulated distributions

Applicable to various coin operators like Hadamard, Grover, Fourier

Provides a mathematical tool for analyzing qubit systems

Abstract

Theoretical and applied studies of quantum walks are abundant in quantum science and technology thanks to their relative simplicity and versatility. Here we derive closed-form expressions for the probability distribution of quantum walks on a line. The most general two-state coin operator and the most general (pure) initial state are considered in the derivation. The general coin operator includes the common choices of Hadamard, Grover, and Fourier coins. The method of Fibonacci-Horner basis for the power decomposition of a matrix is employed in the analysis. Moreover, we also consider mixed initial states and derive closed-form expression for the probability distribution of the Quantum walk on a line. To prove the accuracy of our derivations, we retrieve the simulated probability distribution of Hadamard walk on a line using our closed-form expressions. With a broader perspective in mind, we argue that our approach has the potential to serve as a helpful mathematical tool in obtaining precise analytical expressions for the time evolution of qubit-based systems in a general context.