# Mach-Zehnder interferometer using frequency-domain beamsplitter

## TL;DR

This paper demonstrates a frequency-domain Mach-Zehnder interferometer capable of high-visibility first-order interference between different wavelengths, with potential applications in quantum information processing.

## Contribution

It introduces a novel frequency-domain MZI using nonlinear optics in lithium niobate, achieving high visibility and analyzing its feasibility for quantum applications.

## Key findings

- Visibility over 0.99 at 50% conversion efficiency
- Feasibility of single photon interference with visibility above 0.9
- Potential for quantum information processing applications

## Abstract

We demonstrated the first-order interference between coherent light at 1580 nm and 795 nm by using frequency-domain Mach-Zehnder interferometer (MZI). The MZI is implemented by two frequency-domain BSs based on a second-order nonlinear optical effect in a periodically-poled lithium niobate waveguide with a strong pump light. We achieved the visibility of over 0.99 at 50% conversion efficiencies of the BSs. Toward photonic quantum information processing, sufficiently small background photon rate is necessary. From the measurement results with a superconducting single photon detector, we discuss the feasibility of the frequency-domain MZI in a quantum regime. Our estimation shows that single photon interference with the visibility above 0.9 is feasible with practical settings.