  We report the experimental demonstration of efficient interaction of multi
kilo electron Volt heralded x-ray photons with a beam splitter. The measured
heralded photon rate at the outputs of the beam splitter is about 0.01 counts/s
which is comparable to the rate in the absence of the beam splitter. We use
this beam splitter together with photon number and photon energy resolving
detectors to show directly that single x ray photons cannot split. Our
experiment demonstrates the major advantage of x rays for quantum optics: the
possibility to observe experimental results with high fidelity and with
negligible background.
