Nearly Perfect Transmission and Transformation of Entangled States in Topologically Protected Channels

Abstract

Realization of robust transmission and transformation of entangled states with high fidelity is crucial for the applications in quantum information, computing, and communications. However, it is hard to achieve currently because of scattering loss and disorder. Here, an inverse-design scheme is theoretically proposed and experimentally demonstrated to realize nearly perfect transmission and transformation of entangled photon states. The scheme is based on the determination of the transmission and transformation properties of entangled states, which depends on the overlap integrals among the initial states, eigenmodes of the system and target states. Thus, topologically protected channels are designed according to the requirements for the overlap integrals of these states. As a result, robust transmission and transformation of entangled states are achieved with high fidelity. The proposed scheme has been demonstrated experimentally using the constructed quantum walk platform. This work interconnects topology, quantum physics, and inverse design, and opens up a new avenue for quantum engineering.

Topologically protected entanglement switching around exceptional points

“…The problem is that the fidelities of entangled states become very low after these reported topologically protected operations. Although the transformation efficiency of entangled states can be improved by using inverse-design method 16 , 17 , various parameters need to be designed for the transformation between different entangled states. Moreover, the signal also scatters to non-topologically protected channels, resulting in significant losses in the transformation of entangled states.…”

Highly Efficient Transfer of Quantum State and Robust Generation of Entanglement State Around Exceptional Lines

“…[4,5] Around or near the EPs, DOI: 10.1002/lpor.202300794 the abrupt nature of the phase transitions has been shown to lead to many intriguing phenomena, such as topological mode and energy transfers, [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] laser mode selectivity, [42][43][44] EPenhanced mode splitting, [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] lossinduced transparency, [61,62] unidirectional invisibility [63] and many others. [64][65][66][67] Additionally, the coherent flow induced by exceptional points has been experimentally demonstrated in optics, [68] and quantum Liouvillian exception points in open systems have been studied. [69][70][71] In contrast to...…”

“…[ 4,5 ] Around or near the EPs, the abrupt nature of the phase transitions has been shown to lead to many intriguing phenomena, such as topological mode and energy transfers, [ 27–41 ] laser mode selectivity, [ 42–44 ] EP‐enhanced mode splitting, [ 45–60 ] loss‐induced transparency, [ 61,62 ] unidirectional invisibility [ 63 ] and many others. [ 64–67 ] Additionally, the coherent flow induced by exceptional points has been experimentally demonstrated in optics, [ 68 ] and quantum Liouvillian exception points in open systems have been studied. [ 69–71 ] In contrast to the isolated EPs, the eigenvector and eigenenergy of the system degenerate in many positions, these degenerate points are connected, and their tracks form lines, which are called exceptional lines (ELs).…”