期刊
PHYSICAL REVIEW A
卷 96, 期 1, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevA.96.012111
关键词
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资金
- Swiss National Science Foundation (SNSF) [200021_ 149109]
- Austrian Science Fund (FWF) [J3462]
- COST Action [MP1006]
- European Research Council (ERC MEC)
- Austrian Science Fund (FWF) [J3462] Funding Source: Austrian Science Fund (FWF)
- Swiss National Science Foundation (SNF) [200021_149109] Funding Source: Swiss National Science Foundation (SNF)
Assuming a well-behaving quantum-to-classical transition, measuring large quantum systems should be highly informative with low measurement-induced disturbance, while the coupling between system and measurement apparatus is fairly simple and weak. Here, we show that this is indeed possible within the formalism of quantum mechanics. We discuss an example of estimating the collective magnetization of a spin ensemble by simultaneous measuring three orthogonal spin directions. For the task of estimating the direction of a spin-coherent state, we find that the average guessing fidelity and the system disturbance are nonmonotonic functions of the coupling strength. Strikingly, we discover an intermediate regime for the coupling strength where the guessing fidelity is quasioptimal, while the measured state is almost not disturbed.
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