# A Modulator-Free Quantum Key Distribution Transmitter Chip

## TL;DR

This paper introduces a compact, scalable, and power-efficient quantum key distribution transmitter chip that encodes quantum signals at high rates without traditional modulators, advancing practical quantum communication networks.

## Contribution

The authors present a novel modulator-free integrated quantum transmitter using injection-locking for high-speed phase encoding, improving scalability and energy efficiency.

## Key findings

- Achieved record secure key rates under multiple protocols.
- Demonstrated high-speed, power-efficient quantum encoding on a chip.
- Enabled practical integration of quantum key distribution in networks.

## Abstract

Quantum key distribution (QKD) has convincingly been proven compatible with real life applications. Its wide-scale deployment in optical networks will benefit from an optical platform that allows miniature devices capable of encoding the necessarily complex signals at high rates and with low power consumption. While photonic integration is the ideal route toward miniaturisation, an efficient route to high-speed encoding of the quantum phase states on chip is still missing. Consequently, current devices rely on bulky and high power demanding phase modulation elements which hinder the sought-after scalability and energy efficiency. Here we exploit a novel approach to high-speed phase encoding and demonstrate a compact, scalable and power efficient integrated quantum transmitter. We encode cryptographic keys on-demand in high repetition rate pulse streams using injection-locking with deterministic phase control at the seed laser. We demonstrate record secure-key-rates under multi-protocol operation. Our modulator-free transmitters enable the development of high-bit rate quantum communications devices, which will be essential for the practical integration of quantum key distribution in high connectivity networks.

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Source: https://tomesphere.com/paper/1904.02486