Novel method for preparing high-indistinguishable coherent states

Physical optics

The preparation of indistinguishable quantum states by remote users is one of the crucial tasks in MDI-QKD. To solve this problem, laser injection techniques or modulation of the CW laser on the transceiver side are used. These techniques require a complex setup or a pair of modulators. Here we present a different setup for generating coherent states, using one modulator and one gain-switched laser per transceiver, to find a balance between the complexity of the setup and its cost. The level of indistinguishability achieved allows our scheme to be used in high-speed MDI-QKD protocols.