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

## TL;DR

This paper develops a theoretical framework to analyze the interference effects between Autler-Townes peaks in multi-level atomic systems, revealing how interference nature can be controlled by system parameters.

## Contribution

It introduces a new theoretical approach to identify and understand interference between AT peaks in multi-level systems, including how to tune interference in four-level systems.

## Key findings

- Interference between AT peaks can be pair-wise similar to multi-slit interference.
- In three-level systems, interference nature depends on decay rates.
- In four-level systems, interference can be tuned from constructive to destructive by laser power.

## Abstract

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. The destructive interference between the AT peaks, gives rise to sharp transparency window known as electromagnetically induced transparency (EIT). In the three-level system, the two AT peaks interferes pair-wise with each other, almost similar to the two-slit interference. In the four-level system, the interference between the three AT peaks is also pair-wise 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 zero/no interference) between the two AT peaks is purely determined by the natural decay rate of the states coupled by the control laser. 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 laser.