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In Bell test experiments, there may be problems of experimental design or set-up that affect the validity of the experimental findings. These problems are often referred to as "loopholes". See the article on Bell's theorem for the theoretical background to these experimental efforts (see also J.S. Bell). The purpose of the experiment is to test whether nature is best described using a local hidden variable theory or by the quantum entanglement theory of quantum mechanics. The "detection efficiency", or "fair sampling" problem is the most prevalent loophole in optical experiments. Another loophole that has more often been addressed is that of communication, i.e. locality. There is also the "disjoint measurement" loophole which entails multiple samples used to obtain correlations as compared to "joint measurement" where a single sample is used to obtain all correlations used in an inequality. To date, no test has simultaneously closed all loopholes. Ronald Hanson of Delft University of Technology claims the first Bell experiment that closes both the detection and the communication loopholes.〔()〕 (This was not an optical experiment in the sense discussed below; the entangled degrees of freedom were electron spins rather than photon polarization.) Nevertheless, correlations of classical optical fields also violate Bell's inequality.〔http://arxiv.org/pdf/1506.01305v2.pdf - Shifting the Quantum-Classical Boundary: Theory and Experiment for Statistically Classical Optical Fields〕 In some experiments there may be additional defects that make "local realist" explanations of Bell test violations possible;〔Santos, E., The failure to perform a loophole-free test of Bell’s Inequality supports local realism. Foundations of Physics 34: 1643-1673 (2004)〕 these are briefly described below. Many modern experiments are directed at detecting quantum entanglement rather than ruling out local hidden variable theories, and these tasks are different since the former accepts quantum mechanics at the outset (no entanglement without quantum mechanics). This is regularly done using Bell's theorem, but in this situation the theorem is used as an entanglement witness, a dividing line between entangled quantum states and separable quantum states, and is as such not as sensitive to the problems described here. In October 2015, scientists from the Kavli Institute of Nanoscience reported that the quantum entanglement phenomenon is strongly supported based on a "loophole-free Bell test" study. ==Loopholes== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Loopholes in Bell test experiments」の詳細全文を読む スポンサード リンク
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