Tan Xiangguan, Zhang Yuxia, Qiu Tianhui
College of Electronic and Information Engineering, Shandong University of Science and Technology, Qingdao, 266590, China.
School of Science, Qingdao University of Technology, Qingdao, 266520, China.
Sci Rep. 2024 May 2;14(1):10139. doi: 10.1038/s41598-024-60742-y.
In this paper, we investigate the violation of the quantum witness, the entropic Leggett-Garg inequality (LGI) and the no-coherence-generating-and-detecting (NCGD) dynamics, under projective and coarsening measurements. We consider a qubit in the three scenarios: coherent dynamics, in the presence of dissipation, and in the presence of dephasing. For the pure qubit, we find that in the case of the projective measurement, the non-violation conditions of the quantum witness and the NCGD are the same; while the non-violation conditions of the entropic LGI and the quantum witness do not contain each other, i.e., a suitable conjunction of the quantum witness and the entropic LGI may be better for testing macrorealism. Also, for the pure qubit with coarsening measurement similar results can be obtained. For the dissipative qubit with projective measurement, the quantum witness and the NCGD can be both violated for a wider parameter regime than the entropic LGI. For the dissipative qubit with coarsening measurement, the violation of the NCGD is the most robust compared to the quantum witness and the entropic LGI. For the dephasing qubit with projective and coarsening measurements, the relationship among the quantum witness, the entropic LGI and the NCGD is similar to that of the pure qubit. In addition, we find that for pure, dissipative and dephasing qubits, the robustness of the coarsening measurement in final resolution is more vulnerable than that of the coarsening measurement in reference for the entropic LGI.
在本文中，我们研究了在投影测量和粗粒化测量下量子见证者、熵的莱格特 - 加格不等式（LGI）以及无相干生成与检测（NCGD）动力学的违背情况。我们考虑一个量子比特在三种情形下的情况：相干动力学、存在耗散时以及存在退相时。对于纯量子比特，我们发现，在投影测量的情况下，量子见证者和NCGD的非违背条件是相同的；而熵的LGI和量子见证者的非违背条件并不相互包含，即量子见证者和熵的LGI的适当结合可能更有利于检验宏观实在论。同样，对于进行粗粒化测量的纯量子比特，也能得到类似结果。对于进行投影测量的耗散量子比特，在比熵的LGI更宽的参数范围内，量子见证者和NCGD都可能被违背。对于进行粗粒化测量的耗散量子比特，与量子见证者和熵的LGI相比，NCGD的违背最为稳健。对于进行投影测量和粗粒化测量的退相量子比特，量子见证者、熵的LGI和NCGD之间的关系与纯量子比特的情况类似。此外，我们发现，对于纯量子比特、耗散量子比特和退相量子比特，就熵的LGI而言，最终分辨率下粗粒化测量的稳健性比参考情况下粗粒化测量的稳健性更易受到影响。
