# Low-loss polarization control in fiber systems for quantum computation

## TL;DR

This paper presents a low-loss polarization control method in fiber systems that maintains high interference visibility for quantum computing, using fiber stretchers to optimize polarization states.

## Contribution

The authors introduce a novel polarization control technique that minimizes optical loss while maximizing interference visibility in fiber-based quantum systems.

## Key findings

- Maintained over 99.9% visibility for three hours
- Used fiber stretchers with 0.02 dB loss
- Enhanced fiber system suitability for quantum computing

## Abstract

Optical quantum information processing exploits interference of quantum light. However, when the interferometer is composed of optical fibers, degradation of interference visibility due to the finite polarization extinction ratio becomes a problem. Here we propose a method to optimize interference visibility by controlling the polarizations to a crosspoint of two circular trajectories on the Poincar\'{e} sphere. Our method maximizes visibility with low optical loss, which is essential for quantum light, by using fiber stretchers as polarization controllers. We also experimentally demonstrate our method, where the visibility was maintained basically above 99.9% for three hours using fiber stretchers with an optical loss of 0.02 dB (0.5%). Our method makes fiber systems promising for practical fault-tolerant optical quantum computers.