Quantum key distribution protocol with slow basis change

In many quantum key distribution (QKD) protocols, the receiver has to randomly change a measurement basis for each pulse or each train of pulses. This random change requires us to generate a huge amount of random numbers. It is also cumbersome for some QKD protocols, such as the round-robin differential phase shift QKD protocol, to change the basis rapidly. In this presentation, we address these issues by analyzing the security of QKD protocols with slow basis change. In particular, we show a sufficient condition that allows a QKD protocol to employ the slow basis change. It turns out that the slow basis change does not compromise the key generation rate in a relatively high loss regime when we change the basis as frequently as the photon detection events. Our security proof relaxes technological demands on the receiver side without frustrating the performance.