森 雄一朗 氏（東大/高エネルギー加速器研究機構理論センター）令和元年11月12日
Kochi University of Technology
Unified Quantum Device Laboratory Seminar
⭐Speaker: Mr. Yuichiro Mori (U. Tokyo / KEK Theory Center).
⭐Date&Time : 11 / 12 / 2019 (Fri) 16:40-17:50
⭐Place: Kami Campus, room B107
⭐Title: On the Validity of Weak Measurement applied for Precision Measurement
Aharonov’s weak value A_w, which is defined with using the observable A linearly, can take any complex value. The weak value can be obtained by averaging the outputs of the measuring instrument in a weak measurement as well as the expectation value can be obtained by averaging the outputs in a standard measurement. Consequently, the averaged outputs of the measuring instrument can be larger than that is reachable in the standard measurement. Weak value amplification is an application of this property and it has been used intensively in recent years for precision measurement. However, this does not come for free. In fact, the price we pay for amplifying the weak value is that the rate of passing the screening at postselection is diminished, which implies that we obtain only scanty data if we amplify too much, causing unwanted noise to invalidate what we have measured. This problem is well studied in some models. However, all these studies are based on some models of noise and/or disturbance despite that these elements are intrinsically difficult to pin down in practice. We present a general framework of examining the validity of weak measurement to deal with measurement uncertainty in the weak measurement in which the trade-off relation between the amplification factor and the level of uncertainty can be discussed explicitly and analyze the validity of the two seminal experiments.
Y. Mori, J. Lee and I. Tsutsui, J. Phys. B in press 2019; arXiv:1901.06831