Controlled multi-photon subtraction with cascaded Rydberg superatoms as single-photon absorbers

TL;DR

This paper demonstrates precise control of multi-photon subtraction using cascaded Rydberg superatoms, enabling the removal of up to three photons from light pulses with high fidelity, advancing quantum light state engineering.

Contribution

The work introduces a novel cascaded Rydberg atom system for controlled multi-photon subtraction, with experimental demonstration and theoretical analysis of fidelity limitations.

Findings

Achieved subtraction of up to three photons experimentally.

Identified Raman decay as the main source of infidelity.

Scheme can scale to higher photon subtraction with reduced decay.

Abstract

The preparation of light pulses with well-defined quantum properties requires precise control at the individual photon level. Here, we demonstrate exact and controlled multi-photon subtraction from incoming light pulses. We employ a cascaded system of tightly confined cold atom ensembles with strong, collectively enhanced coupling of photons to Rydberg states. The excitation blockade resulting from interactions between Rydberg atoms limits photon absorption to one per ensemble and engineered dephasing of the collective excitation suppresses stimulated re-emission of the photon. We experimentally demonstrate subtraction with up to three absorbers. Furthermore, we present a thorough theoretical analysis of our scheme where we identify weak Raman decay of the long-lived Rydberg state as the main source of infidelity in the subtracted photon number. We show that our scheme should scale well to higher absorber numbers if the Raman decay can be further suppressed.