Nature of interference between Autler–Townes peaks in generic multi-level system

In this work we present a theoretical frame work to identify the role and the nature of interference between Autler–Townes (AT) peaks (or dressed states) in generic multi-level system. In three-level system, the two AT peaks interfere pair-wise with each other, almost similar to the two-slit interference. In four-level system, the interference between the three AT peaks is also pair-wise only with no higher order of interference analogous to three-slit interference but has a bit more complicated nature of interference. However, in many practical situations in atomic systems only the simple form of interference similar to three-level system dominates. In the three-level system, the nature of interference (i.e. constructive, destructive or no interference) between the two AT peaks is purely determined by the natural decay rate of the states coupled by the control laser(s). However, in four-level system the nature of interference between the two extreme AT peaks can be tuned from constructive to destructive by tuning the power of the control lasers.