Microwave Photon Echoes from Polyethylene

Photon echoes have been generated in a coaxial cable at frequencies between 1 and 2 GHz. The echoes originate in electric dipole transitions within the inhomogeneously broadened tunneling systems of the partially disordered polyethylene of the cable dielectric. The two-pulse photon echo has been observed in the temperature region between 0.01 and 1.0 K and exhibits a weak decay with time, $\tau$ as $\exp (-\alpha {\tau }^{\frac{1}{2}})$.