  Based on the three-level quantum system, when it is in resonance, according
to any two lattice points closest to Hamiltonian coupling, electrons transition
from high energy level to low energy level and release photons; Or absorb
photons and transition from low energy level to high energy level, thus
obtaining the physical process of quantum walking along a straight line under
the condition of equal probability. Then, the optical radiation in the quantum
walk is mapped into a Gaussian pulse of the electric field, and the Maxwell's
equation is solved by the three dimensional finite-difference time-domain
method to obtain the spatial electric distributio. Finally, the physical
process ofquantum walking on two parallel lines is further discussed, involving
some physical properties such as electromagnetic coupling or coherence, quantum
state exchange and so on. The electric field coupling between two lines can be
calculated by FDTD, which provides a useful tool for the design and analysis of
quantum devices.
