New scheme for measurement-device-independent quantum key distribution

We propose a new scheme for measurement-device-independent quantum key distribution (MDI-QKD) with a two-mode state source. In this scheme, the trigger state is split into different paths and detected at both senders; thus, four types of detection events can be obtained. Based on these events, the signal state is divided into four non-empty sets that can be used for parameter estimation and key extraction. Additionally, we carry out a performance analysis on the scheme with two-intensity (vacuum state and signal state) heralded single-photon sources. We also numerically study the statistical fluctuation in the actual system. Our simulations show that the error rate and the secure transmission distance of our two-intensity scheme are better than those of existing three- and four-intensity MDI-QKD schemes with different light sources. Considering statistical fluctuations, the maximum secure distance of our scheme can reach 344 km when the data length is 10¹³ and remains as long as 250 km when the data length is 10¹⁰. Moreover, our scheme improves the system performance and reduces the challenges of implementing the system.