Deterministic generation of hybrid entangled states using quantum walks

Recently, hybrid entanglement (HE), which involves entangling a qubit with a coherent state, has demonstrated superior performance in various quantum information processing tasks, particularly in quantum key distribution [arXiv:2305.18906 (2023)]. Despite its theoretical advantages, the practical generation of these states in the laboratory has been a challenge.

In this context, we introduce a deterministic and efficient approach for generating HE states using quantum walks. Our method achieves a remarkable fidelity of 99.90 % with just 20 time steps in a one-dimensional split-step quantum walk. This represents a significant improvement over prior approaches that yielded HE states only probabilistically, often with fidelities as low as 80%. Our scheme not only provides a robust solution to the generation of HE states but also highlights a unique advantage of quantum walks, thereby contributing to the advancement of this burgeoning field. Moreover, our scheme is experimentally feasible with the current technology.