40 km Fiber Transmission of Squeezed Light Measured with a Real Local Oscillator

TL;DR

This paper demonstrates the generation and 40 km fiber transmission of squeezed light at 1550 nm, using a real local oscillator with real-time phase control, suitable for long-distance quantum communication.

Contribution

It introduces a stable, telecom-compatible system for transmitting and measuring squeezed states over long distances with a real local oscillator and FPGA control.

Findings

Achieved 3.7 dB noise suppression after 40 km fiber transmission

Maintained phase noise uncertainty around 2.5 degrees

Used standard telecom components for a compact setup

Abstract

We demonstrate the generation, 40 km fiber transmission, and homodyne detection of single-mode squeezed states of light at 1550 nm using real-time phase control of a locally generated local oscillator, often called a "real local oscillator" or "local local oscillator". The system was able to stably measure up to around 3.7 dB of noise suppression with a phase noise uncertainty of around 2.5$^\circ$, using only standard telecom-compatible components and a field-programmable gate array (FPGA). The compactness, low degree of complexity and efficacy of the implemented scheme makes it a relevant candidate for long distance quantum communication in future photonic quantum networks.