论文标题
QCD中带有顶级夸克的量子信息
Quantum information with top quarks in QCD
论文作者
论文摘要
顶级夸克代表了独特的高能系统，因为可以测量它们的自旋相关性，从而可以研究高能煤层的Qubits的量子力学基本方面。我们在这里介绍了高能对撞机的量子染色体动力学（QCD）产生的顶级态度（$ t \ bar {t} $）的量子状态的一般框架。我们认为，通常根据生产旋转密度矩阵给出了可以在对撞机中探测的总量子状态，这必然导致混合状态。我们计算从最基本的QCD过程产生的$ t \ bar {t} $对的量子状态，在不同的相位空间的不同区域中发现纠缠和违反CHSH的存在。我们表明，$ t \ bar {t} $ pair的任何现实的HADRONIC生产都是这些基本QCD过程的统计混合物。我们专注于在LHC和Tevatron上进行的质子 - 蛋白质和质子 - 抗蛋白碰撞的实验相关病例，分析了量子状态与碰撞能量的依赖性。我们为纠缠和CHSH侵入性特征提供实验性可观察物。在LHC上，这些签名是通过对单个可观察的可观察到的，在纠缠的情况下，这代表了违反cauchy-schwarz的不平等现象。我们将文献中提出的$ t \ bar {t} $对的量子断层扫描协议的有效性扩展到更通用的量子状态以及任何生产机制。最后，我们认为在对撞机中测量的CHSH违规只是违反贝尔定理的一种薄弱形式，必然包含许多漏洞。
Top quarks represent unique high-energy systems since their spin correlations can be measured, thus allowing to study fundamental aspects of quantum mechanics with qubits at high-energy colliders. We present here the general framework of the quantum state of a top-antitop ($t\bar{t}$) quark pair produced through quantum chromodynamics (QCD) in a high-energy collider. We argue that, in general, the total quantum state that can be probed in a collider is given in terms of the production spin density matrix, which necessarily gives rise to a mixed state. We compute the quantum state of a $t\bar{t}$ pair produced from the most elementary QCD processes, finding the presence of entanglement and CHSH violation in different regions of phase space. We show that any realistic hadronic production of a $t\bar{t}$ pair is a statistical mixture of these elementary QCD processes. We focus on the experimentally relevant cases of proton-proton and proton-antiproton collisions, performed at the LHC and the Tevatron, analyzing the dependence of the quantum state with the energy of the collisions. We provide experimental observables for entanglement and CHSH-violation signatures. At the LHC, these signatures are given by the measurement of a single observable, which in the case of entanglement represents the violation of a Cauchy-Schwarz inequality. We extend the validity of the quantum tomography protocol for the $t\bar{t}$ pair proposed in the literature to more general quantum states, and for any production mechanism. Finally, we argue that a CHSH violation measured in a collider is only a weak form of violation of Bell's theorem, necessarily containing a number of loopholes.
