Reconfigurable Quantum Key Distribution

Quantum key distribution (QKD) enables information-theoretically secure key exchange between two remote parties. However, practical implementations often are vulnerable to device imperfections, particularly in the state preparation. In this paper, we propose a reconfigurable QKD scheme based on arbitrary pure states. By reducing the number and accuracy of required quantum states, our approach simplifies implementation while enhancing robustness against practical imperfections. Within this framework, the communicating parties can dynamically reconfigure their system, adaptively selecting a subset of states based on the raw key, to implement various QKD protocols. We prove that the security of the proposed scheme can be reduced to that of standard QKD protocols with mutually unbiased bases and full quantum state preparation, thereby inheriting the established security proofs of existing QKD protocols. To the best of our knowledge, the proposed scheme imposes the loosest and most straightforward requirements on state preparation, making it the most simplified QKD scheme to date. Notably, this reconfiguration provides greater resilience against state preparation flaws and can be seamlessly integrated into current systems without requiring any hardware modifications. Our work bridges the gap between theoretical security and practical implementation, paving the way for more reliable QKD deployments in real-world scenarios.