Miklos Redei, Stephen J. Summers
We propose some formulations of the notion of "operational independence" of two subsystems of a larger quantum system and clarify their relation to other independence concepts in the literature. In addition, we indicate why the operational independence of quantum subsystems holds quite generally, both in nonrelativistic and relativistic quantum theory.
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Operationally independent events can influence each other in quantum theory
该研究证伪了量子理论中的经典独立性概念，基于量子网络框架和Clauser-Horne-Shimony-Holt不等式构建线性见证量，并探讨了经典独立性最大违背在设备无关量子态与测量认证中的应用。
Whether a quantum computation employs nonlocal resources is operationally undecidable
本研究证明量子计算是否采用非局域资源在操作上不可判定，指出MIP*协议中验证者无法区分MIP*机器与单片量子计算机，相关资源使用理论分析不可靠，对量子计算框架评估有实际意义。
Understanding the core content of quantum mechanics requires us to disentangle the hidden logical relationships between the postulates of this theory. Here we show that the mathematical structure of quantum measurements, the formula for assigning outcome probabilities (Born's rule) and the post-measurement state-update rule, can be deduced from the other quantum postulates, often referred to as "unitary quantum mechanics", and the assumption that ensembles on finite-dimensional Hilbert spaces are characterised by finitely many parameters. This is achieved by taking an operational approach to p…
The trace distance between two quantum states, $ρ$ and $σ$, is an operationally meaningful quantity in quantum information theory. However, in general it is difficult to compute, involving the diagonalization of $ρ- σ$. In contrast, the Hilbert-Schmidt distance can be computed without diagonalization, although it is less operationally significant. Here, we relate the trace distance and the Hilbert-Schmidt distance with a bound that is particularly strong when either $ρ$ or $σ$ is low rank. Our bound is stronger than the bound one could obtain via the norm equivalence of the Frobenius and trace…
Operationally induced preferred basis in unitary quantum mechanics
OIPB框架通过探测器接口诱导基底选择，基于Gleason型唯一性推导Born规则，与退相干和操作理论一致，但与坍缩模型和多世界解释不同。
Semi-device-independent randomness certification on discretized continuous-variable platforms
本文提出一种针对连续变量实现的半设备无关随机性认证方案，通过限制光子态制备到二能级福克子空间，证明在存在现实损耗和参考系偏移的情况下，简单光学装置可实现维度见证违反，认证正min-熵。
In quantum cryptography, device-independent (DI) protocols can be certified secure without requiring assumptions about the inner workings of the devices used to perform the protocol. In order to display nonlocality, which is an essential feature in DI protocols, the device must consist of at least two separate components sharing entanglement. This raises a fundamental question: how much entanglement is needed to run such DI protocols? We present a two-device protocol for DI random number generation (DIRNG) which produces approximately $n$ bits of randomness starting from $n$ pairs of arbitrari…
Quantum correlations and Basis-Independent Coherence Distribution in Two Gravitational Cat States
该研究分析了双势阱中通过引力耦合的两粒子的量子关联与基矢无关的相干性分布，发现局域相干性比集体相干性更抗热涨落，增大引力耦合可优先增强集体相干性。
Operational simultaneous correlations in complementary bases of bipartite states via one-sided semi-device-independent steering
本文利用单侧半设备无关量子导引，为二分态互无偏基中的操作同时关联提供可操作的量化与分类，并通过量子导引椭球给出几何可视化。
We characterize operationally meaningful quantum gains in a paradigmatic model of lossless multiple-phase interferometry and stress insufficiency of the analysis based solely on the concept of quantum Fisher information. We show that the advantage of the optimal simultaneous estimation scheme amounts to a constant factor improvement when compared with schemes where each phase is estimated separately -- contrary to a widely cited results claiming a better precision scaling in terms of the number of phases involved.
Demonstration of unpartible entanglement
通过可重构时间复用干涉仪产生两模双光子态，并利用量子态层析验证了模式无关纠缠的存在，证明纠缠在模式变换下依然保持。
The recently developed framework for quantum theory with no global causal order allows for quantum processes in which operations in local laboratories are neither causally ordered nor in a probabilistic mixture of definite causal orders. The causal relation between the laboratories is described by the process matrix. We show that, if the inputs of the laboratories are measured in a fixed basis, one can introduce an effective process matrix which is operationally indistinguishable from the original one. This effective process matrix can be obtained by applying the von Neumann- Luders update rul…
Semi-Device-Independent Quantum Key Distribution from Operational Assumptions
研究半设备无关量子密钥分发，基于爱丽丝四重制备系综对源做操作假设，推导随机访问码经典边界，通过三设置扩展获安全证书，结果表明其安全性不仅取决于伊芙识别能力，还取决于其排除能力。
The standard formulation of quantum theory relies on a fixed space-time metric determining the localisation and causal order of events. In general relativity, the metric is influenced by matter, and is expected to become indefinite when matter behaves quantum mechanically. Here, we develop a framework to operationally define events and their localisation with respect to a quantum clock reference frame, also in the presence of gravitating quantum systems. We find that, when clocks interact gravitationally, the time localisability of events becomes relative, depending on the reference frame. Thi…
Typical thermalization of low-entanglement states
本文针对低纠缠初始态，通过定义局域哈密顿量上的随机能量平滑，在具有操作意义的精确条件下证明了封闭量子系统的局域热化，并证明该变换不影响局域 Gibbs 态和短时动力学。
One of the key ways in which quantum mechanics differs from relativity is that it requires a fixed background reference frame for spacetime. In fact, this appears to be one of the main conceptual obstacles to uniting the two theories. Additionally, a combination of the two theories is expected to yield non-classical, or "indefinite", causal structures. In this paper, we present a background-independent formulation of the process matrix formalism - a form of quantum mechanics that allows for indefinite causal structure - while retaining operationally well-defined measurement statistics. We do t…
Saturable global quantum sensing
本文提出一种面向操作的全局量子传感方法，在固定但优化的测量与探针设置下获得可饱和精度界限，适用于玻色子高斯和自由费米子传感器，并揭示了最优测量随先验宽度变化的规律。
Two-point measurement correlations beyond the quantum regression theorem
本文超越量子回归定理，提出稳健方法揭示非马尔可夫开放系统中回归假设失效所反映的纠缠、相干性及量子记忆等基本量子特征，并关联至浴谱密度与热流等微观性质。
Thermal Time and Irreversibility from Non-Commuting Observables in Accelerated Quantum Systems
研究热时间在相对论量子场论中如何通过局部探测器模型成为操作意义，发现当状态满足KMS条件且探测器通过非对易可观测量耦合时，可区分性出现。
Exclusion reshapes the operational manifestation of preparation contextuality
本文研究了在无奇偶约束下，排除替代检索任务如何改变准备上下文性的操作表现，发现排除在量子领域具有优势，而检索则没有。通过引入POREC码，证明了在素数符号大小m下，经典和非准备上下文编码提供了紧致的非上下文界限，而首个非平凡情况下的精确量子位最优解违反了这一界限。
Quantifying the intrinsic randomness of quantum measurements
本文研究噪声量子测量中窃听者 Eve 对结果的最大猜测概率，证明在广义测量与混合态情形下，经典关联和量子关联策略会导致不同的内禀随机性界定。
Negative probability values have been widely employed as an indicator of the nonclassicality of quantum systems. Known as a quasiprobability distribution, they are regarded as a useful tool that provides significant insight into the underlying fundamentals of quantum theory when compared to the classical statistics. However, in this approach, an operational interpretation of these negative values with respect to the definition of probability---the relative frequency of occurred event---is missing. An alternative approach is therefore considered where the quasiprobability operationally reveals …
Macroscopic Realism (MR) says that a macroscopic system is always determinately in one or other of the macroscopically distinguishable states available to it. The Leggett-Garg (LG) inequality was derived to allow experimental test of whether or not this doctrine is true; it is also often thought of as a temporal version of a Bell-inequality. Despite recent interest in the inequality, controversy remains regarding what would be shown by its violation. Here we resolve this controversy, which arises due to an insufficiently general and model-independent approach to the question so far. We argue t…
Adversarial Stress Tests for Quantum Certification
本文提出了一种半设备无关的认证框架，通过分析统计偏差与操作模型的对齐性，定义了鲁棒性缺口，以区分统计波动与模型误差。
When Isolated Quantum Systems Appear Classical
本文通过严格界限推导出孤立量子系统在大多数时间操作上不可区分于经典混合态的充分条件，揭示了内在平衡机制可导致经典行为，无需环境退相干。
The presence of contextuality in quantum theory was first highlighted by Bell, Kochen and Specker, who discovered that for quantum systems of three or more dimensions, measurements cannot be viewed as revealing pre-existing properties of the system. More precisely, no model can assign deterministic outcomes to the projectors of a quantum measurement in a way that depends only on the projector and not the context (the full set of projectors) in which it appeared, despite the fact that the Born rule probabilities associated with projectors are independent of the context. A more general, operatio…
When Does Quantum Differential Privacy Compose?
本文研究了量子差分隐私的组合问题，发现经典方法在量子场景中失效，提出基于矩会计的新框架以实现有效的组合保证。
Events as Spacetime Anchors: Local Irreversibility at the Interface of Quantum Field Theory and Relativity
研究探讨量子场论与相对论中事件锚定问题，提出以事件为中心框架，通过局部经典化等三个条件表征事件锚定，在重复碰撞开放系统模型中实现，该框架解决事件何时成稳定时空事实问题，与标准理论兼容且不涉及事件生成相关问题。
Operational Coherent Measurements with Steering and Randomness
本文证明测量集合可用于半设备无关导引当且仅当其相干，并基于此提出一种无需纠缠认证且容忍任意低探测效率的量子随机数生成方案。
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