# Suppressing deleterious effects of spontaneous emission in creating bound states in cold atom continuum

## TL;DR

This paper proposes a method using vacuum-induced coherence to suppress spontaneous emission, enabling the creation of bound states in the continuum in cold atoms, which was previously hindered by decay effects.

## Contribution

It introduces a novel approach employing vacuum-induced coherence to counteract spontaneous emission, facilitating the experimental realization of bound states in continuum in cold atom systems.

## Key findings

- Vacuum-induced coherence can cancel spontaneous emission effects.
- Microwave dressing of molecular states achieves necessary conditions for VIC.
- Proposes a feasible experimental setup for BIC in cold atoms.

## Abstract

In a previous paper [B. Deb and G. S. Agarwal, Phys. Rev. A 90, 063417 (2014)], it was theoretically shown that, magneto-optical manipulation of low energy scattering resonances and atom-molecule transitions could lead to the formation of a bound state in continuum (BIC), provided there is no spontaneous emission. We find that even an exceedingly small spontaneous decay from exited molecular states can spoil the BIC. In this paper, we show how to circumvent the detrimental effect of spontaneous emission by making use of vacuum-induced coherence (VIC) which results in the cancellation or suppression of spontaneous emission. VIC occurs due to the destructive interference between two spontaneous decay pathways. An essential condition for VIC is the non-orthogonality of the transition dipole moments associated with the decays. Furthermore, the interference between decay pathways requires that the spacing between the two decaying states must be comparable to or smaller than the square root of the product of the two spontaneous linewidths. We demonstrate that these conditions can be fulfilled by microwave dressing of two appropriately chosen molecular excited states, opening a promising prospect for the experimental realization of BIC of cold atoms.