We ask the question how the (weak) equivalence principle established in classical gravitational physics should be reformulated and interpreted for massive quantum objects that may also have internal degrees of freedom (dof). This inquiry is necessary because even elementary concepts like a classical trajectory are not well defined in quantum physics -- trajectories originating from quantum histories become viable entities only under stringent decoherence conditions. From this investigation we posit two logically and operationally distinct statements of the equivalence principle for quantum systems: Version A: The probability distribution of position for a free-falling particle is the same as the probability distribution of a free particle, modulo a mass-independent shift of its mean. Version B: Any two particles with the same velocity wave-function behave identically in free fall, irrespective of their masses. Both statements apply to all quantum states, including non-classical ones, and also for composite particles with quantum internal dof. We also investigate the consequences of the interaction between internal and external dof induced by free fall. For a class of initial states, we find a dephasing for the translational dof, namely, the suppression of the off-diagonal terms of the density matrix, in the position basis. We also find a gravitational phase shift in the reduced density matrix of the internal dof that does not depend on the particle's mass. For classical states, the phase shift has a natural classical interpretation in terms of gravitational red-shift and special relativistic time-dilation.
Equivalence Principle and Field Quantization in Curved Spacetime
为了遵守等效原理，弯曲时空中的场只能在每个点的邻域内量子化，在那里可以构造一个自由下落的具有z e r o曲率的M i n k o w s k i标架。在每一个这样的坐标系中，引力的几何力都可以被一个自相互作用的自旋为2的场所代替，正如费曼在1962年提出的那样。在距离黑洞一个固定的距离$R$处，每个自由下落的体积元中的真空就像是一个热浴，所有粒子的温鲁温度T_U= \hbar GM/2πc R ^2。在视界R= 2 GM/c^2处，下降真空的Hawking温度T_H= \hbar c^3/8πGMk_B。
Equivalence of the measures of non-Markovianty for open two-level systems
为了刻画开放系统中量子时间演化偏离马尔可夫过程的程度，人们提出了不同的度量。我们证明了Breuer，Laine和Piilo [Phys. Rev. Lett. 103，210401（2009）]和Rivas，Huelga和Plenio [Phys. Rev. Lett. 105，050403（2010）]具有完全相同的非马尔可夫时间演化间隔，因此当它们应用于通过Jaynes-Cummings模型或退相模型耦合到环境的开放两能级系统时，它们实际上彼此等价。这种等价性意味着这三种测度以不同的方式捕捉到了量子演化过程的非马尔可夫性的本质特征。我们还表明，在第一个措施的定义中的最大化，实际上可以删除所考虑的模型，而不影响检测非马尔可夫性的措施的灵敏度。
Spontaneous wave function collapse from non-local gravitational self-energy
State University of Tetovo（泰托沃国立大学）；California State University, Fresno（加州州立大学弗雷斯诺分校）；Universidade de Lisboa（里斯本大学）；Instituto de Astrofísica e Ciências do Espaco（天文与空间科学研究所）
Mixed-state phases induced by power-law quantum channels
Joint Quantum Institute, NIST/University of Maryland（联合量子研究所，美国国家标准与技术研究院/马里兰大学）；Joint Center for Quantum Information and Computer Science, NIST/University of Maryland（联合量子信息与计算机科学中心，美国国家标准与技术研究院/马里兰大学）；Department of Physics and Astronomy, Center for Quantum Research and Technology, University of Oklahoma（俄克拉荷马大学物理与天文学系、量子研究与技术中心）
