Time- and frequency-domain polariton interference
  We present experimental observations of interference between an atomic spin coherence and an optical field in a {\Lambda}-type gradient echo memory. The interference is mediated by a strong classical field that couples a weak probe field to the atomic coherence through a resonant Raman transition. Interference can be observed between a prepared spin coherence and another propagating optical field, or between multiple {\Lambda} transitions driving a single spin coherence. In principle, the interference in each scheme can yield a near unity visibility. 
G. T. Campbell, M. Hosseini, B. M. Sparkes, P. K. Lam, B. C. Buchler
quant-ph