Semiquantum key distribution using initial states in only one basis without the classical user measuring

TL;DR

This paper introduces a novel semiquantum key distribution protocol that minimizes quantum resources by restricting the quantum user to one basis and removing the classical user's measurement, while maintaining security.

Contribution

It presents the first SQKD protocol with a single-basis quantum user and no measurement capability for the classical user, proving its unconditional security.

Findings

Protocol is unconditionally secure.

Achieves key distribution with minimal quantum resources.

Provides a key rate expression in the asymptotic limit.

Abstract

From the perspective of resource theory, it is interesting to achieve the same quantum task using as few quantum resources as possible. Semiquantum key distribution (SQKD), which allows a quantum user to share a confidential key with a classical user who prepares and operates qubits in only one basis, is an important example for studying this issue. To further limit the quantum resources used by users, in this paper, we constructed the first SQKD protocol which restricts the quantum user to prepare quantum states in only one basis and removes the classical user's measurement capability. Furthermore, we prove that the constructed protocol is unconditionally secure by deriving a key rate expression of the error rate in the asymptotic scenario. The work of this paper provides inspiration for achieving quantum superiority with minimal quantum resources.