Blind quantum computation over a collective-noise channel

TL;DR

This paper introduces a method for blind quantum computation over noisy channels using decoherence-free subspaces, enhancing security and robustness in long-distance quantum communication.

Contribution

It proposes three DFS-based protocols for BQC that maintain security and improve noise resilience, including a novel coherent-light-assisted scheme.

Findings

DFS effectively mitigates collective noise in quantum channels

Protocols preserve unconditional security despite noise

The coherent-light-assisted protocol improves transmission fidelity

Abstract

Blind quantum computation (BQC) allows a client (Alice), who only possesses relatively poor quantum devices, to delegate universal quantum computation to a server (Bob) in such a way that Bob cannot know Alice's inputs, algorithm, and outputs. The quantum channel between Alice and Bob is noisy, and the loss over the long-distance quantum communication should also be taken into account. Here we propose to use decoherence-free subspace (DFS) to overcome the collective noise in the quantum channel for BQC, which we call DFS-BQC. We propose three variations of DFS-BQC protocols. One of them, a coherent-light-assisted DFS-BQC protocol, allows Alice to faithfully send the signal photons with a probability proportional to a transmission rate of the quantum channel. In all cases, we combine the ideas based on DFS and the Broadbent-Fitzsimons-Kashefi protocol, which is one of the BQC protocols, without degrading unconditional security. The proposed DFS-based schemes are generic and hence can be applied to other BQC protocols where Alice sends quantum states to Bob.