Sending-or-not-sending twin-field protocol for quantum key distribution with asymmetric source parameters

The sending-or-not-sending (SNS) protocol of the twin-field quantum key distribution can tolerate large misalignment error and its key rate can exceed the linear bound of repeaterless quantum key distribution. But the original SNS protocol requires the two users to use the same source parameters. Here we propose an SNS protocol with asymmetric source parameters and give the security proof of this protocol. Our asymmetric protocol has a much better performance than that of the original SNS protocol when the channel is asymmetric.