Quantum key distribution with limited classical Bob

TL;DR

This paper introduces two robust quantum key distribution protocols involving a limited classical Bob, and leverages their features to develop a quantum secure direct communication method for transmitting secret messages without prior key sharing.

Contribution

The paper presents novel QKD protocols with a limited classical Bob and demonstrates their application in secure direct communication, expanding the scope of practical quantum communication.

Findings

Protocols are proven to be completely robust.

Limited classical Bob can deterministically choose bits.

A new quantum secure direct communication protocol is constructed.

Abstract

Two QKD protocols with limited classical Bob who performs only limited classical operations (preparing a (fresh) qubit in the classical basis and send it or doing nothing) are presented and are proved completely robust. As limited classical Bob can deterministically choose the bits, we use the feature to construct a quantum secure direct communication protocol, which is the direct communication of secret messages without first producing a shared secret key.