Spatial and spectral coherent control with frequency combs

Quantum coherent control(1-6) is a powerful tool for steering the outcome of quantum processes towards a desired final state by the accurate manipulation of quantum interference between multiple pathways. Although coherent control techniques have found applications in many fields of science(7-12), the possibilities for spatial and high-resolution frequency control have remained limited. Here, we show that the use of counter-propagating broadband pulses enables the generation of fully controlled spatial excitation patterns. This spatial control approach also provides decoherence reduction, which allows the use of the high-frequency resolution of an optical frequency comb(13,14). We exploit the counter-propagating geometry to perform spatially selective excitation of individual species in a multicomponent gas mixture, as well as frequency determination of hyperfine constants of atomic rubidium with unprecedented accuracy. The combination of spectral and spatial coherent control adds a new dimension to coherent control, with applications in nonlinear spectroscopy, microscopy and high-precision frequency metrology, among others.