Related Experiment Video
Updated: Aug 24, 2026

Conducting Hyperscanning Experiments with Functional Near-Infrared Spectroscopy
Published on: January 19, 2019
Observation of antinormally ordered Hanbury Brown-Twiss correlations
Koji Usami1, Yoshihiro Nambu, Bao-Sen Shi
1Department of Material Science and Engineering, Tokyo Institute of Technology, Yokohama 226-0026, Japan. usami@frl.cl.nec.co.jp
Abstract:
We have measured antinormally ordered Hanbury Brown-Twiss correlations for coherent states of the electromagnetic field by using a stimulated parametric down-conversion process. Photons were detected by stimulated emission, rather than by absorption, so that the detection responded not only to actual photons but also to zero-point fluctuations via spontaneous emission. The observed correlations were distinct from normally ordered ones as they showed excess positive correlations, i.e., photon bunching effects, which arose from the thermal nature of zero-point fluctuations.
Related Concept Videos
Correlation of Experimental Data
For example, a spherical particle moving through a viscous fluid experiences drag. Dimensional analysis shows that the drag force depends on the particle's diameter, velocity, and...
Correlations
Friedman Two-way Analysis of Variance by Ranks
Correlation
Two variables, for example, a and b, are said to be positively correlated if both variables move in the same direction. In other words, a positive correlation exists between two variables, a and b, if:
Spearman's Rank Correlation Test
Spearman's test calculates correlation by...
Correspondence Bias

