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arXiv 1004.0377quant-phcs.CC
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量子建议的一个完整特征

A Full Characterization of Quantum Advice

Scott Aaronson, Andrew Drucker

摘要:

我们证明了以下令人惊讶的结果:给定n个量子比特上的任何量子态rho,在poly(n)量子比特上存在局部哈密顿量H(例如,两量子比特相互作用的总和),使得H的任何基态都可以用于在固定多项式大小的所有量子线路上模拟ρ。就复杂性类而言,这意味着BQP/qpoly包含在QMA/poly中,这取代了Aaronson之前的结果,即BQP/qpoly包含在PP/poly中。事实上,我们可以准确地描述量子建议,在力量上等同于不可信的量子建议与可信的经典建议的结合。证明我们的主要结果需要结合大量以前的工具-包括Alon等人关于实值概念类学习的结果,Aaronson关于量子态可学习性的结果,以及Aharonov和Regev关于“QMA+超级验证器”的结果-并且还创建了一些新的工具。主要的新工具是所谓的多数证书引理,它与机器学习的提升密切相关,并且似乎有可能找到独立的应用。在最简单的版本中,这个引理说如下。给定n个变量的布尔函数的任意集合S,S中的任意函数f都可以表示为m=O(n)个函数f1,...,fm在S中,使得每个fi是S中与O(log |S|)输入/输出约束兼容的唯一函数。

英文摘要:

We prove the following surprising result: given any quantum state rho on n qubits, there exists a local Hamiltonian H on poly(n) qubits (e.g., a sum of two-qubit interactions), such that any ground state of H can be used to simulate rho on all quantum circuits of fixed polynomial size. In terms of complexity classes, this implies that BQP/qpoly is contained in QMA/poly, which supersedes the previous result of Aaronson that BQP/qpoly is contained in PP/poly. Indeed, we can exactly characterize quantum advice, as equivalent in power to untrusted quantum advice combined with trusted classical advice. Proving our main result requires combining a large number of previous tools -- including a result of Alon et al. on learning of real-valued concept classes, a result of Aaronson on the learnability of quantum states, and a result of Aharonov and Regev on "QMA+ super-verifiers" -- and also creating some new ones. The main new tool is a so-called majority-certificates lemma, which is closely related to boosting in machine learning, and which seems likely to find independent applications. In its simplest version, this lemma says the following. Given any set S of Boolean functions on n variables, any function f in S can be expressed as the pointwise majority of m=O(n) functions f1,...,fm in S, such that each fi is the unique function in S compatible with O(log|S|) input/output constraints.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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