一个相对相位决定有噪声贝尔对的操作阈值
One Relative Phase Orders Operational Thresholds of Noisy Bell Pairs
- Stony Brook University（石溪大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文证明，对于任意噪声的贝尔混合态，其操作阈值由上界决定，且噪声与贝尔相干性间的相对相位单调控制阈值，并可通过部分层析成像认证能力。
AI中文摘要：
与两量子比特纠缠集和CHSH非局域集不同，可导引集和贝尔非局域集没有已知的一般闭式判据。对于任何此类操作能力，若其失效态构成在局域酉变换下封闭的凸集，并且对于具有任意噪声的贝尔混合态，噪声的$X$部分给出了确定性阈值的上界，即混合态获得该能力所需的贝尔权重之上界。该上界是固定$X$部分的十五个泡利期望值中七个所能支持的最紧上界。同一定理表明，若状态的$X$部分具有该能力，则状态本身也具有该能力，因此对状态的部分层析成像可以认证其能力。当噪声具有$X$形式时，混合态携带噪声与贝尔相干性之间的相对相位，该相位无法通过局域酉变换消除，并通过干涉控制阈值。我们证明了一个单调性定律：无论该能力是否存在闭式判据，阈值在该相位下都是非递减的。
英文摘要：
Unlike the two-qubit entangled and CHSH-nonlocal sets, the steerable and Bell-nonlocal ones have no known general closed-form criterion. For any such operational ability whose failing states form a convex set closed under local unitaries, and for a Bell mixture with arbitrary noise, the $X$ part of the noise gives an upper bound on the definitive threshold, the Bell weight above which the mixture attains the ability. That bound is the tightest that the seven of the fifteen Pauli expectation values fixing the $X$ part can support. The same theorem shows that a state has the ability whenever its $X$ part does, so partial tomography of a state can certify its ability. When noise is of $X$ form, the mixture carries a relative phase between the noise and Bell coherences that cannot be gauged away by local unitaries, and it controls the threshold through interference. We prove a monotonicity law: the threshold is nondecreasing in this phase, whether or not a closed-form criterion for the ability exists.
