Mimicking the Hadamard discrete-time quantum walk with a time-independent Hamiltonian

TL;DR

This paper demonstrates that a carefully optimized time-independent Hamiltonian can mimic the dynamics of a Hadamard discrete-time quantum walk, including probability distribution, entanglement, and transition to classical behavior.

Contribution

It introduces a novel approach to replicate quantum walk dynamics using a single, time-independent Hamiltonian, simplifying the model and broadening understanding of quantum simulations.

Findings

Time-independent Hamiltonian can approximate quantum walk dynamics

Optimized parameters reproduce probability distribution and entanglement

Classical regime equivalence confirmed

Abstract

The discrete-time quantum walk dynamics can be generated by a time-dependent Hamiltonian, repeatedly switching between the coin and the shift generators. We change the model and consider the case where the Hamiltonian is time-independent, including both the coin and the shift terms in all times. The eigenvalues and the related Bloch vectors for the time-independent Hamiltonian are then compared with the corresponding quantities for the effective Hamiltonian generating the quantum walk dynamics. Restricted to the non-localized initial quantum walk states, we optimize the parameters in the time-independent Hamiltonian such that it generates a dynamics similar to the Hadamard quantum walk. We find that the dynamics of the walker probability distribution and the corresponding standard deviation, the coin-walker entanglement, and the quantum-to-classical transition of the discrete-time quantum walk model can be approximately generated by the optimized time-independent Hamiltonian. We, further, show both dynamics are equivalent in the classical regime, as expected.