Improving resilience of quantum-gravity-induced entanglement of masses to decoherence using three superpositions
Improving resilience of quantum-gravity-induced entanglement of masses to decoherence using three superpositions
复制标题
使用三种叠加提高量子引力引起的质量纠缠对退相干的恢复能力
作者：
M. Schut;J. Tilly;Ryan J. Marshman;S. Bose;A. Mazumdar
最近提出了一种称为量子引力诱导质量纠缠（QGEM）的协议，旨在使用2个量子比特的纠缠来测试引力的量子性质。只有当两个空间叠加的质量之间的力通过中介虚引力子的交换发生时，纠缠才能出现。在本文中，我们研究了QGEM设置的可能改进，通过引入嵌入量子位的第三质量，现在有3个量子位来见证引力产生的纠缠。我们比较了不同的实验设置与2和3量子比特的纠缠产生，发现3量子比特的设置，其中叠加是相互平行的导致最高的纠缠产生率在$\tau = 5 $ s。我们将证明，3量子位设置对更高的退相干率更具弹性。如果退相干率$\gamma$<0.11 $ Hz，而3-qubit设置的$\gamma <0.16 $ Hz，则可以在实验上检测到2-qubit设置的纠缠。然而，引入额外的量子位意味着需要更多的测量来表征实验中的纠缠。我们进行了实验模拟和估计，3量子比特的设置将允许检测在QGEM协议中的纠缠在$O（10^4）-O（10^5）$测量时，$\gamma \在[0.1，0.15] $ Hz $99.9\%$的确定性。此外，我们发现，所需的测量的数量可以减少到O（10^3）-O（10^5）$，如果测量时间表是使用联合泡利基测量优化。对于$\gamma>0.06 $ Hz，3-qubit设置与2-qubit设置相比在表征纠缠所需的最小测量次数方面是有利的。因此，这里提出的设置提供了一个有前途的新途径，实现QGEM实验。
Recently a protocol called quantum gravity induced entanglement of masses (QGEM) that aims to test the quantum nature of gravity using the entanglement of 2 qubits was proposed. The entanglement can arise only if the force between the two spatially superposed masses is occurring via the exchange of a mediating virtual graviton. In this paper, we examine a possible improvement of the QGEM setup by introducing a third mass with an embedded qubit, so that there are now 3 qubits to witness the gravitationally generated entanglement. We compare the entanglement generation for different experimental setups with 2 and 3 qubits and find that a 3-qubit setup where the superpositions are parallel to each other leads to the highest rate of entanglement generation within $\tau = 5 $ s. We will show that the 3-qubit setup is more resilient to the higher rate of decoherence. The entanglement can be detected experimentally for the 2-qubit setup if the decoherence rate $\gamma$ is $\gamma<0.11 $ Hz compared to $\gamma<0.16 $ Hz for the 3-qubit setup. However, the introduction of an extra qubit means that more measurements are required to characterize entanglement in an experiment. We conduct experimental simulations and estimate that the 3-qubit setup would allow detecting the entanglement in the QGEM protocol at a $99.9\%$ certainty with $O(10^4)-O(10^5)$ measurements when $\gamma \in [0.1,0.15] $ Hz. Furthermore, we find that the number of needed measurements can be reduced to $O(10^3)-O(10^5)$ if the measurement schedule is optimised using joint Pauli basis measurements. For $\gamma>0.06 $ Hz the 3-qubit setup is favourable compared to the 2-qubit setup in terms of the minimum number of measurements needed to characterize the entanglement. Thus, the proposed setup here provides a promising new avenue for implementing the QGEM experiment.
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