= Fermionic atom antibunching
The 2007 paper <Comparison of the Hanbury Brown-Twiss effect for bosons and fermions by T. Jeltes and others> compares polarized <helium-3> <fermions> with <helium-4> <bosons>. The <chemical atoms> occupy a <metastable atomic level>. Switching off <magnetic trapping of neutral atoms> releases them onto a <microchannel plate detector> with a delay-line anode, 63 cm below. Position and arrival-time readouts give three-dimensional pair separations by <time-of-flight atom detection>. About 1000 clouds per <isotope> supply <histograms>; normalization removes the broad cloud shape.
The <pair detection correlation> dips below one for <helium-3> and rises above one for <helium-4>. The same apparatus, matched <temperatures> near $0.5\,\mu\mathrm K$, nearly identical trapping potentials, negligible interactions, and <magnetic field> gradient checks of <spin> polarization support an exchange-statistics interpretation. Finite detector resolution suppresses contrast; trap switch-off and resolution uncertainties limit quantitative agreement. A diverging <laser> lens deepens the dip, but its aberrations preclude a precise lens-model test. This detects exchange correlations, rather than measuring occupation of one selected <spin orbital>.<Comparison of the Hanbury Brown-Twiss effect for bosons and fermions by T. Jeltes and others>[pp. 3–7, Methods, Figs. 1–3; supplementary pp. 14–16]{ref}
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