# Remote blind state preparation with weak coherent pulses in the field

## TL;DR

This paper demonstrates a practical, long-distance remote blind quantum state preparation protocol using weak coherent pulses, enabling secure quantum cloud computing over 100 km fiber with high fidelity.

## Contribution

The authors propose and experimentally verify a resource-efficient remote blind qubit preparation protocol suitable for long-distance quantum communication.

## Key findings

- Successfully generated 1000 secure qubits with high fidelity
- Demonstrated protocol over 100 km fiber in the field
- Fidelity exceeds quantum no-cloning limit

## Abstract

Quantum computing has seen tremendous progress in the past years. Due to the implementation complexity and cost, the future path of quantum computation is strongly believed to delegate computational tasks to powerful quantum servers on cloud. Universal blind quantum computing (UBQC) provides the protocol for the secure delegation of arbitrary quantum computations, and it has received significant attention. However, a great challenge in UBQC is how to transmit quantum state over long distance securely and reliably. Here, we solve this challenge by proposing and demonstrating a resource-efficient remote blind qubit preparation (RBQP) protocol with weak coherent pulses for the client to produce, using a compact and low-cost laser. We demonstrate the protocol in field, experimentally verifying the protocol over 100-km fiber. Our experiment uses a quantum teleportation setup in telecom wavelength and generates $1000$ secure qubits with an average fidelity of $(86.9\pm1.5)\%$, which exceeds the quantum no-cloning fidelity of equatorial qubit states. The results prove the feasibility of UBQC over long distances, and thus serving as a key milestone towards secure cloud quantum computing.