High efficiency in mode selective frequency conversion

TL;DR

This paper analyzes the limitations of frequency conversion efficiency in quantum protocols, identifies time-ordering corrections as a key factor, and proposes cascaded architectures and Magnus expansion techniques to mitigate these effects and enhance efficiency.

Contribution

It introduces a new understanding of efficiency limits via time-ordering corrections and suggests novel cascaded and Magnus expansion methods to improve mode-selective frequency conversion.

Findings

TOCs limit upconversion efficiency to around 80%

Cascaded FC protocols act as attenuators of TOCs

Magnus expansion can be used to increase conversion efficiency

Abstract

Frequency conversion (FC) is an enabling process in many quantum information protocols. Recently, it has been observed that upconversion efficiencies in single-photon, mode-selective FC are limited to around 80%.In this letter we argue that these limits can be understood as time-ordering corrections (TOCs) that modify the joint conversion amplitude of the process. Furthermore we show, using a simple scaling argument, that recently proposed cascaded FC protocols that overcome the aforementioned limitations act as "attenuators" of the TOCs. This observation allows us to argue that very similar cascaded architectures can be used to attenuate TOCs in photon generation via spontaneous parametric down-conversion. Finally, by using the Magnus expansion, we argue that the TOCs, which are usually considered detrimental for FC efficiency, can also be used to increase the efficiency of conversion in partially mode selective FC.