Comments on "An experimental test of non-local realism" by S. Groeblacher, T. Paterek, R. Kaltenbaek, C. Bruckner, M. Zukovski, M. Aspelmeyer, and A. Zeilinger, Nature 446 (2007), 871-875
A simple proof of a key inequality required by the paper's analysis is presented. An introductory section discussing the paper's setup may be helpful to some readers. An alternative statistical analysis is suggested.
The deep-rooted concept of ``realism''---a viewpoint according to which an external reality exists independent of observation, may have been shaken to some extent by a recent surprising advance in experimental test of a broad class of nonlocal hidden-variable (NLHV) theories [S. Gr\"oblacher, T. Paterek, R. Kaltenbaek, \ifmmode \check{C}\else \v{C}\fi{}. Brukner, M. \ifmmode \dot{Z}\else \.{Z}\fi{}ukowski, M. Aspelmeyer, and A. Zeilinger, Nature (London) 446, 871 (2007)], though there exists a detection loophole. In this paper a feasible propose for a loophole-free test of non-local realism is discussed based on the independent readout of two electron spins of donors 31P in semiconductors in different cavities entangled through a 4.4 dB bright squeezed coherent light and a postselection based on homodyne measurement. The electron spins are read out by using optically induced spin to charge transduction detected by radio-frequency single electron transistor.