We experimentally observe the evolution of two-photon path-entangled states in a planar multimode waveguide, and show how the two-photon correlation recurrence period depends on the relative phase between the two paths.
We study the quantum correlation of path-entangled states of two photons in coupled one-dimensional waveguide arrays with lattice defects. Both off-diagonal and diagonal defects are considered, which show different effects on the quantum correlation of path-entangled two-photon states. Two-photon bunching or anti-bunching effects can be observed and controlled. The two photons are found to have a tendency to bunch at the side lobes with a repulsive off-diagonal defect, and the path-entanglement of the input two-photon state can be preserved during the propagation. We also found that defect modes may play an important role on the two-photon correlation of path-entangled states in the waveguide arrays. Due to the quantum interference effect, intriguing evolution dynamics of the two-photon correlation matrix elements with oscillation frequencies being either twice of or the same as that of a classical light wave, depending on the position of the correlation matrix element, is observed. Our results show that it is possible to manipulate the two-photon correlation properties of path-entangled states in waveguide arrays with lattice defects.
Abstract In this work, we investigate the quantum state reconstruction of the periodic input state in a 1-D waveguide array. In particular, we consider a single-photon multimode entangled W-state with different periodicities as an input to the array and study the effect of periodicity in the output. For comparison, we also study separable single photon periodic input states. We study the evolution of average photon number and the fidelity of the periodic input state and give the exact solution to investigate the revival of single photon multimode periodic input. Our solution is valid for any number of waveguides in the array. Our findings show the revival of the average photon number and almost complete quantum state reconstruction of the initial multimode entangled state for certain periodicities. The results reported here are significant because multimode-entangled states are essential resources for various applications in the physical implementation of photonic quantum technologies.