Quantum photonic integrated circuits at 1550 nm

Project Information

QPIC1550

Grant agreement ID: 101135785

DOI

10.3030/101135785

EC signature date 16 November 2023

Start date 4 December 2023

End date 3 December 2027

Funded under

• Digital, Industry and Space

Total cost

No data

EU contribution

€ 5 998 129,23

Coordinated by

QTI SRL
Italy

Periodic Reporting for period 1 - QPIC1550 (Quantum photonic integrated circuits at 1550 nm)

Reporting period: 2023-12-04 to 2025-06-03

Summary of the context and overall objectives of the project

Quantum photonic integrated circuits (QPICs) operating at the telecom wavelength of 1550 nm are emerging as a foundational technology for quantum communication, computing, and metrology. Their ability to integrate diverse photonic components—such as waveguides, modulators, detectors, and nonlinear materials—onto a single chip enables compact, scalable, and efficient systems for precise single-photon control. Moreover, their compatibility with existing fiber-optic infrastructure makes them a practical and cost-effective solution for real-world quantum applications.

Despite the maturity of photonic integrated circuits in classical optics, adapting them for quantum technologies presents significant challenges. These include the need for high-performance, easily integrable sources and detectors of single and entangled photons, as well as mitigating noise, losses, and environmental instabilities. This project aims to address these limitations by developing a universal PIC platform based on InAs/InP quantum dots and InGaAs/InP detectors, integrated on a silicon nitride platform. Operating at 1550 nm, this platform will support advanced quantum functionalities with improved reliability, scalability, and integration potential.

Key objectives include the creation of high-performance InAs/InP quantum dot sources for single and entangled photons, and the integration of InGaAs/InP single-photon avalanche diodes (SPADs) with SiN waveguides. These components will enable scalable, low-noise, and efficient quantum photonic integrated circuits. The project also introduces the QPIC1550 platform, which combines active InP-based devices with low-loss SiN passives, supporting a wide range of quantum functionalities. This includes the demonstration of fully integrated quantum key distribution (QKD) systems using the BB84 protocol, offering improved stability, cost-efficiency, and scalability.

Building on this foundation, the project will demonstrate the first network of QPICs for Remote Quantum Computing, using deterministic quantum dot sources and low-loss SiN receivers connected via telecom fiber. A theoretical framework will be developed to support distributed quantum processing across multiple nodes. Additionally, the project will showcase quantum clock synchronization using entangled photon sources and detectors, targeting sub-picosecond precision over distances up to 20 km. These demonstrations will highlight the potential of QPIC1550 technology to enable scalable, high-performance quantum networks for communication, computing, and time synchronization.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Key achievements include the successful fabrication of quantum dot (QD) sources in InAs/InP and InGaAs/InAlAs systems, with low fine structure splitting and emission at telecom wavelengths. Two generations of p-i-n QD devices were produced, and InP photonic cavities with QDs were optimized for integration with SiN via micro-transfer printing. SiN circuits were fabricated for initial experiments, and cryogenic packaging tests began. In parallel, InGaAs/InP SPADs were developed for both hybrid and heterogeneous integration with SiN waveguides, along with dedicated read-out electronics.

The project also advanced the integration of III-V components onto SiN platforms using AN800 LGTF 200mm wafer technology. First-generation passive chips were fabricated, followed by a dedicated run producing 168 chips and six patterned wafers for active integration. These chips are now being tested for the four target applications. Packaging designs for room-temperature PICs were completed, with two already delivered for testing. Intermediate-temperature SPAD packaging is in early development, while cryogenic packaging structures are undergoing validation. These efforts collectively lay the groundwork for scalable, high-performance quantum photonic systems tailored to real-world applications.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Given the early stage of the project, currently available results going beyond the state of the art are mainly related to device fabrication and characterisation. The following results have been published in scientific journals and are listed as publications related to the project.

The first result is related to the controlled growth of InAs/InP quantum dots. We have demonstrated the ability to independently tune the surface density and size of QDs by adjusting the conditions of Stranski-Krastanov growth. With this approach, we have demonstrated how the surface density and mean size of QDs can be tuned almost independently from each other. Specifically the QD density can be tuned between 10^7 and 10^9 units per cm^2 by choosing the V/III ratio between 2 and 100.

We developed an alternative technique to electron beam lithography using xenon plasma-focused ion beam (Xe-PFIB) for the fabrication if integrated photonic structures. This approach allows for direct 3D shaping of photonic structures around low-density QDs, overcoming limitations in footprint and photon leakage. The resulting truncated cone-shaped structures significantly enhance photon collection efficiency—up to 90% for a numerical aperture of 0.65—and enable high-purity single-photon emission (~99%) with an extraction efficiency of 24 ± 4% in the telecom C-band.

To support long-term and high-precision optical experiments, a vision-guided stabilization system has been developed. This Python-based software utilizes real-time image correlation techniques from the OpenCV library to automatically correct sample drift with pixel-level accuracy. Designed for near-infrared spectroscopy setups, it addresses the persistent issue of mechanical vibrations and cryostat-induced drift, ensuring consistent excitation and detection from the same sample location over extended periods.