High-rate and high-capacity measurement-device-independent quantum key distribution with Fibonacci matrix coding in free space

Abstract

This paper proposes a high-rate and high-capacitymeasurement-device-independent quantum key distribution (MDI-QKD)protocol with Fibonacci-valued and Lucas-valued orbital angularmomentum (OAM) entangled states in free space. In the existingMDI-OAM-QKD protocols, the main encoding algorithm handles encodednumbers in a bit-by-bit manner. To design a fast encoding algorithm,we introduce a Fibonacci matrix coding algorithm, by which, encodednumbers are separated into segments longer than one bit. By doingso, when compared to the existing MDI-OAM-QKD protocols, the newprotocol can effectively increase the key rate and the codingcapacity. This is because Fibonacci sequences are used in preparingOAM entangled states, reducing the misattribution errors (which slowdown the execution cycle of the entire QKD) in QKD protocols.Moreover, our protocol keeps the data blocks as small as possible,so as to have more blocks in a given time interval. Mostimportantly, our proposed protocol can distill multiple Fibonaccikey matrices from the same block of data, thus reducing thestatistical fluctuations in the sample and increasing the final QKDrate. Last but not the least, the sender and the receiver can omitclassical information exchange and bit flipping in the secure keydistillation stage.