Control of Four-Level Quantum Coherence via Discrete Spectral Shaping of an Optical Frequency Comb

TL;DR

This paper demonstrates precise control of a four-level atomic system using a femtosecond frequency comb, highlighting the importance of spectral phase shaping and optimizing pulse shapes to enhance two-photon transition rates.

Contribution

It introduces a method for high-resolution coherent control of a four-level system via spectral phase shaping of an optical frequency comb, achieving significant transition rate enhancement.

Findings

Phase coherence established between two-photon transitions in cold Rb atoms.

Spectral phase control influences the optical response of the system.

Pulse shaping increases two-photon transition rate by 256%.

Abstract

We present an experiment demonstrating high-resolution coherent control of a four-level atomic system in a closed (diamond) type configuration. A femtosecond frequency comb is used to establish phase coherence between a pair of two-photon transitions in cold Rb atoms. By controlling the spectral phase of the frequency comb we demonstrate the optical phase sensitive response of the diamond system. The high-resolution state selectivity of the comb is used to demonstrate the importance of the signs of dipole moment matrix elements in this type of closed-loop excitation. Finally, the pulse shape is optimized resulting in a 256% increase in the two-photon transition rate by forcing constructive interference between the mode pairs detuned from an intermediate resonance.