Perfect state transfer in quantum photonic networks based on Fourier modes
We propose a quantum network consisting of optical waveguides in the linear regime for quantum state transfer. The circular topology of our network introduces novel functionalities that enable us to analytically identify the conditions under which perfect state transfer (PST) is achievable. We utilize the properties of the Fourier modes, in particular the zero Fourier modes, which provide a protected subspace for the efficient propagation of quantum states, resulting in PST to the diametrically opposite site in a network with any number of sites $N = 4n$. The coupling profiles in the photonic network modulate the number of zero-energy eigenmodes, with uniform couplings yielding more than evanescent ones, confirming that the expedition of observed PST originates from the collapse of the eigenvalue spectrum into three distinct eigenvalue blocks, including $N/2$ manifolds of zero Fourier modes. We investigate PST in both discrete- and continuous-variable input regimes, using single photon state, Schr\"odinger cat states, and two-mode squeezed vacuum state. Our findings apply to the engineering of quantum networks and photonic lattices, paving the way for applications in controlled routing in integrated quantum circuits.