Speaker
Description
Quantum walks provide a powerful platform for exploring non-classical transport phenomena and for designing controllable quantum dynamics in discrete systems. Here, we investigate the transport properties of a one-dimensional discrete-time quantum walk driven by a three-qubit Greenberger–Horne–Zeilinger (GHZ) entangled coin state, focusing on the contrasting effects of position-dependent (PD) and position-independent (PI) coin operators. The quantum evolution is analyzed under two distinct conditional shift protocols for a range of rotation angles $\theta$, with the resulting dynamics characterized through position-space probability distributions and Shannon entropy. We demonstrate that the combined influence of multipartite coin entanglement, coin rotation, spatial dependence, and the choice of conditional shift operator enables precise control over quantum transport. In the limiting cases $\theta=0$ and $\theta=\pi/2$, the dynamics recover transport regimes analogous to those observed in Bell-state quantum walks, whereas intermediate rotation angles exhibit distinct spreading behaviors ranging from boundary-peaked ballistic transport to enhanced spatial delocalization. The evolution of Shannon entropy provides a quantitative characterization of these transitions, revealing the role of GHZ-induced coherence and interference in shaping the walker dynamics. Our results establish position-dependent operations on multipartite entangled coin states as a versatile approach for controlling transport and localization phenomena in quantum walks, with potential applications in quantum simulation, quantum information processing, and programmable quantum transport systems.
