Gigahertz-rate thin-film lithium niobate receiver for time-bin quantum communication

TL;DR

This paper presents a fully integrated, high-speed quantum receiver on a thin-film lithium niobate platform capable of active manipulation and measurement of time-bin quantum states, advancing scalable quantum communication.

Contribution

It introduces a novel, high-bandwidth, integrated quantum receiver that enables active switching and measurement of time-bin states, improving security and flexibility in quantum communication.

Findings

Achieved electro-optic bandwidth exceeding 30 GHz for active switching.

Demonstrated Bell's inequality violation with 38 standard deviations.

Realized stable quantum key distribution with over 25 kbit/s over 12 hours.

Abstract

Time-bin encoded quantum states of light are crucial for quantum technology applications. The integration of manipulation functionalities into chip-scale devices is essential for deploying scalable, high-performance, and cost-effective quantum networks. Here we develop a fully integrated, high-throughput quantum receiver based on the thin-film lithium niobate (TFLN) platform, capable of high-speed electro-optic manipulation of time-bin encoded quantum states. The device's novel architecture enables active switching of time-bin quantum states with an electro-optic bandwidth exceeding 30 Ghz, while supporting real-time arbitrary projective measurements with a bandwidth of over 1 GHz. We showcase its versatility and performance through several applications, including the certification of entanglement with Bell's inequality violation by 38 standard deviations and with >95% visibility. We then apply it to a fiber-based quantum communication scenario, where we experimentally demonstrate an entanglement-based quantum key distribution (QKD) protocol, achieving stable finite-size secure key rates exceeding 25 kbit/s over 12 hours of continuous operation. By leveraging a high-speed active switching scheme, the system overcomes the need for temporal post-selection, eliminating a fundamental loophole that compromises the security of time-bin entanglement-based QKD protocols and relaxes the temporal resolution requirements of single-photon detectors. Moreover, it enables active selection of the projection basis, increasing the flexibility for communication parties. This approach establishes a versatile and scalable architecture for time-bin encoded quantum communication, enabling practical protocols on industry-grade photonic technology.