Verifying the observer dependence of quasiparticle counts in the   analogue gravity of dilute ultracold quantum gases
  The quasiparticle content of a quantum field depends on the observer, in particular on its motional state, on the way the observer's detector couples to the quantum field, and on the frequency standard in which the detector carried by the observer measures the quanta to be detected. I review a procedure of making this fundamental property of quantum field theory experimentally manifest using quantum-optical means in Bose-Einstein condensates. 
Uwe R. Fischer
cond-mat.quant-gas gr-qc quant-ph