Molecular cooling via Raman transitions and a harmonic spectral modulation of an optical frequency comb: The role of the parity of the chirp in quantum control

TL;DR

This paper presents a method for creating ultracold molecules using an optical frequency comb with spectral phase modulation, highlighting how the parity of the chirp affects quantum control and decoherence mitigation.

Contribution

It introduces a novel spectral phase modulation technique for optical frequency combs that enhances molecular cooling by controlling quantum states through chirp parity.

Findings

Sinusoidal spectral phase modulation creates quasi-dark states reducing decoherence.

Cosine modulation does not produce the same quasi-dark state.

Parity of the spectral chirp is crucial for effective quantum control.

Abstract

A method for creation of ultracold molecules by stepwise adiabatic passage from the Feshbach state to the fundamentally ground state using an optical frequency comb is presented within a semiclassical multilevel model. The sinusoidal modulation of the spectral phase of the comb is implemented that leads to a creation of a quasi-dark dressed state having an insignificant population of the excited state manifold and, thus, efficiently mitigating decoherence in the system. In contrast, the cosine modulation does not lead to the quasi-dark state formation. The results demonstrate the importance of the parity of the spectral chirp in quantum control.