基于冗余图态的多人协作量子计算

Collaborative quantum computation with redundant graph state

量子计算是一种基于量子力学基本原理设计的新型计算模型,在某些特定问题上表现出了远超经典计算机的处理能力.随着量子计算任务复杂度的提高,如何分配量子计算资源,实现多方协作的量子计算,将成为量子计算领域待解决的一个重要问题.本文在一次性量子计算的基础上,提出了基于冗余图态的多人协作量子计算方案.不同于传统图态中每个节点仅对应一个粒子,冗余图态中每个节点都对应若干粒子.参与量子计算的每一方都将分配到一组完整涵盖各节点的粒子,各方将自行协商完成图态的分割以及后续的测量,从而实现多人协作的量子计算.在本方案中,参与量子计算的各方可以根据自身任务的需要来确定量子计算的合作方式并进行资源分配,使量子计算具备更高的灵活性与开放性.此外,本文还提出了一个两方协作制备任意单比特量子态的光学实验方案.

Quantum computation is a computing model based on quantum theory,which can outperform the classical computation in solving certain problems.With the increase of the complexity of quantum computing tasks,it becomes important to distribute quantum computing resources to multi-parties to cooperatively fulfill the complex tasks.Here in this paper a scheme based on the one-way quantum computing model is proposed to realize collaborative quantum computation.The standard one-way quantum computing model is based on graph states.With graph states used as resources,one can realize a universal quantum computer through using singlequbit measurements and feed-forward.In contrast to the standard one-way computation,the main resource for collaborative quantum computation is a redundant graph state(also a multi-particle highly entangled state).Unlike in the traditional graph state where each particle corresponds to a specific node,in a redundant graph state,several particles correspond to a single node,which means that each node of the graph has several redundant copies.With the help of a redundant graph state,several parties can share a graph state flexibly at will.A redundant graph state is prepared and then distributed to several parties where each of them obtains a full copy of all nodes.By communicating with each other and measuring the particles in different ways,a standard graph state is prepared and distributed among these parties.The collaborative computation then finishes through the common one-way quantum computing operations.Besides the general scheme,a concrete optical implementation of a two-party cooperative single-qubit quantum state preparation based on a six-photon redundant graph state is also put forward.Such a redundant graph state is proposed to be prepared by using the spontaneous parametric down-conversion entangled source and quantum interference.With this redundant graph state,a standard three-node graph state can be shared with the two parties in an arbitrary way.This scheme does not only make the collaborative quantum computation across several parties possible and flexible,but also guarantee the privacy of each party’s operations.This feature would be particularly useful in the case where the computing resource is obtained from an outside provider.This scheme paves the way for realizing quantum computation in more general and complicated applications.