Quantum and classical signal processing with cryogenic rare earth ion dopants - Jevon Longdell

In this talk I will discuss research we are carrying out into the applications of cryogenic rare earth ion dopants. These include developing quantum memories and repeaters for quantum networks, working toward single dopant detection with whispering gallery mode resonators and creating ultrahigh selectivity optical filters for the optical detection of ultrasound. In particular I will discuss two recent achievements: the demonstration of rephased amplified spontaneous emission; and separating the carrier and ultrasonic sidebands on a scattered field with a record 49 dB selectivity. Rare earth ion dopants 4f->4f transitions are used exensively in phosphors for lighting and in solid state laser materials. The reasons for this the low rate of non-radiative decay for some of the optical excited states, leading to millisecond scale lifetimes. At cryogenic (<4K) temperatures the associated optical transitions become astonishingly narrow, being close to lifetime limited in many cases. Homogeneous linewidths of 60 Hz and transitions with Q factors as high as 4x1012 have been observed. Recent advances in closed cycle cryo-coolers makes this narrow linewidth regime much more accessible.