Improving BB84 Efficiency with Delayed Measurement via Quantum Memory

In this paper, we introduce a novel modification to the BB84 Quantum Key Distribution (QKD) protocol, aimed at enhancing its efficiency through the use of quantum memory and delayed measurement. In the standard BB84 protocol, the receiver immediately measures the qubits sent by the sender using randomly chosen bases. Due to mismatches between the sender and receiver's bases, a significant portion of the qubits are discarded, reducing the overall key generation rate. Our proposed protocol allows the receiver to store the received qubits in quantum memory and defer measurement until after the sender reveals her basis choices, effectively eliminating the need to discard mismatched qubits. This modification improves the key generation efficiency while maintaining the core security features of the standard BB84 protocol. By avoiding the unnecessary loss of qubits, our protocol achieves a higher secret key rate without introducing additional vulnerabilities. We present a detailed step-by-step explanation of the delayed measurement process. Although this approach does not alter the security guarantees of BB84, it represents a significant improvement in efficiency, making the protocol more viable for large-scale quantum communication networks.