Wave Function Collapse in a Mesoscopic Device

We determine the non-local in time and space current-current cross correlator $<\widehat{I}(x_1,t_1)\widehat{I}(x_2,t_2)>$ in a mesoscopic conductor with a scattering center at the origin. Its excess part appearing at finite voltage exhibits a unique dependence on the retarded variable $t_1-t_2-(|x_1|-|x_2|)/ v_{\rm\scriptscriptstyle F}$,with$v_{\rm\scriptscriptstyle F}$ the Fermi velocity. The non-monotonic dependence of the retardation on $x_1$ and its absence at the symmetric position $x_1=-x_2$ is a signature of the wave function collapse, which thus becomes amenable to observation in a mesoscopic solid state device.