Phase-controlled coherent dynamics of a single spin under closed-contour interaction

摘要

In three-level quantum systems, interference between two simultaneously driven excitation pathways can give rise to effects such as coherent population trapping(1,2) and electromagnetically induced transparency(3). The possibility to exploit these effects has made three-level systems a cornerstone of quantum optics. Coherent driving of the third available transition forms a closed-contour interaction (CCI), which yields fundamentally new phenomena, including phase-controlled coherent population trapping(4,5) and phase-controlled coherent population dynamics(6). Despite attractive prospects, prevalent dephasing in experimental systems suitable for CCI driving has made its observation elusive(7-10). Here, we exploit recently developed methods for coherent manipulation of nitrogen-vacancy electronic spins to implement and study highly coherent CCI driving of a single spin. Our experiments reveal phase-controlled quantum interference, reminiscent of electron dynamics on a closed loop threaded by a magnetic flux, which we synthesize from the driving-field phase(11). Owing to the nature of the dressed states created under CCI, we achieve nearly two orders of magnitude improvement of the dephasing times, even for moderate drive strengths. CCI driving constitutes a novel approach to coherent control of few-level systems, with potential for applications in quantum sensing or quantum information processing.