Improvement of information leakage resistant quantum dialogue with single photons in both polarization and spatial-mode degrees of freedom

There is a quantum dialogue (QD) protocol by Ye et al. based on single photons in both polarization and spatial-mode degrees of freedom. In order to make two communicants share the initial states of encoding photons, the protocol has employed auxiliary photons the same as encoding ones. However, when they arrive at the responder, auxiliary photons cannot be measured at once. This leads to an extra demand of responders on keeping photons. But the technology of storing photons for some time is difficult to implement at this stage. For this reason, Ye et al.'s QD protocol is lacking in practicability on that. To enhance practicability, the paper uses auxiliary photons different from encoding ones and enables them measured immediately on arrival. This not only is able to make responders know encoding photons' initial states as well, but also does not need to keep photons. This new measure avails of the protocol practicability greatly. So the proposed QD protocol can be thought of as an improvement of Ye et al.'s QD protocol.