Too entangled to quantum compute one-way
Too entangled to quantum compute one-way
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量子计算单向过于纠缠
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
D. Bacon
中科院分区：
文献类型：
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作者：
D. Bacon
利用量子效应的计算机似乎能够超越它们的经典计算机。例如，量子计算机可以有效地因式分解整数，而我们的现代经典计算机还没有已知的算法可以有效地执行此任务[1]。考虑到这种额外的计算能力，一个自然要问的问题是“是什么赋予了量子计算机额外的计算能力？”这个问题本质上是很难的——试着问自己传统经典计算机的力量从何而来，你会发现自己正在思考计算复杂性这个广阔而富有挑战性的领域的核心问题。尽管如此，在回答量子系统何时无法提供计算加速的问题方面已经取得了相当大的成功。纠缠研究中出现了一个特别引人注目的故事——一种特殊的量子力学性质，描述了量子系统各部分之间测量的相互依赖性。这项工作表明，在计算过程中的某个时刻没有足够纠缠的量子系统无法用于构建性能优于经典计算机的量子计算机[2]。由于纠缠量子系统无法通过局部经典理论来复制，因此加速需要纠缠的想法似乎很自然。但现在两个小组 [3, 4] 在《物理评论快报》上发表了论文，提出了令人惊讶的结果：有时过多的纠缠会破坏量子计算机的能力！
Computers that exploit quantum effects appear capable of outperforming their classical brethren. For example, a quantum computer can efficiently factor a whole number, while there is no known algorithm for our modern classical computers to efficiently perform this task [1]. Given this extra computational punch, a natural question to ask is “What gives quantum computers their added computational power?” This question is intrinsically hard—try asking yourself where the power of a traditional classical computer comes from and you will find yourself pondering questions at the heart of the vast and challenging field known as computational complexity. In spite of this, considerable success has been made in answering the question of when a quantum system is not capable of offering a computational speedup. A particularly compelling story has emerged from the study of entanglement—a peculiar quantum mechanical quality describing the interdependence of measurements made between parts of a quantum system. This work has shown that a quantum system without enough entanglement existing at some point in the process of a computation cannot be used to build a quantum computer that outperforms a classical computer [2]. Since entangled quantum systems cannot be replicated by local classical theories, the idea that entanglement is required for speedup seems very natural. But now two groups [3, 4] have published papers in Physical Review Letters that put forth a surprising result: sometimes too much entanglement can destroy the power of quantum computers!