# QKD paper

## Structure of paper

### Introduction

* QKD is important today
* BBM92 is a good protocol to use, as a compromise between key rate and security
* Fiber-based QKD is useful despite the versatility of free-space implementation
* 1310~nm is a good wavelength to use in metropolitan settings
* There are practical advantages of 1310nm being able to run C-band classical traffic
* Existing works are comparable, but we demonstrate with a setup that is designed for portability

### Quantum channel + deployment

Main selling point of the paper.

* We demonstrate continuous QKD run over 9 days with bitrate.
* Rough description of setup and measurement
* Rough description of deployed fiber characteristics
* Active polarization compensation performed

### Clock synchronization


### Classical channel


### Application layer


* Co-propagation achieved in fiber
* QBER contribution

### Discussion



### Comparisons

| Paper | Application | Quantum | Classical | Length | Clocksync |
|--|--|--|--|--|--|
| townsend1997simultaneous | First demo | O-band | C-band | - |
| ✔️ thomas2022entanglement | Entanglement distribution, V=71% | O-band, 417MHz pulsed | C-band, 7dBm | 47km |
| shi2020stable | QKD BBM92 | O-band | - | 10km |
| sanz2025adapting | QKD BBM92 | C-band, Quantum Optics Jena | C-band | 23km |
| clark2025coexistence | QKD BBM92 | C-band | C-band | hollow core |
| fan2023energy | QKD BBM92 | C-band | C-band, 20Gbps | 45km spool |
| krvzivc2023towards | QKD BBM92 | 810nm | - | - | Rb clock |
| pelet2023operational | QKD EB-based?? Homebrew | C-band, SNSPD | - | 50km | Rb clock |
| wang2017long | QKD BB84 | O-band pulsed | C-band | 80km spool |
| ✖️ thomas2023quantum | Teleportation | O-band | C-band | 11km spool |
| wang2024time | QKD BB84, time-MUX | C-band pulsed | C-band, 10dBm | 100km |, as well as strong stimulated Raman and Brioullin scattering
| mao2018integrating | QKD BB84 | O-band | C-band, 21dBm | 66km |