QUANTum communications with Integrated high-dimensional biphoton FrequencY states – QUANTIFY

In recent years, we have witnessed the advent of what is now called the second quantum revolution: whereas previously we essentially observed the quantum nature of physical objects and used their properties at a macroscopic level, we now have the technological capabilities to manipulate these objects individually and make them interact in a controlled way for specific applications. The QUANTIFY project falls within this context, and more precisely within the scope of quantum communication, while keeping in mind the potential for transversal applications of the technology we are developing, in particular in the field of quantum metrology.
The starting point of the project are the AlGaAs sources developed at the MPQ Laboratory, which present several advantages: small footprint (typical volume well below 1mm3), operation at room temperature, emission of entangled photons in the telecommunication C-band, compatibility with electrical injection, high second-order non-linearity, and electro-optical effect. Thanks to the complementary expertise of the consortium members, QUANTIFY's objective is to capitalize on these results, focused on component aspects, and to demonstrate that this platform with its many assets can now lead to high-performance quantum key distribution (QKD) systems.
The work is organized into two main tasks:
In the first part of our project we will work on the improvement of the performance of the multi-user QKD protocol based on entanglement, by exploiting the peculiarity characterizing the state emitted by the AlGaAs sources : wide spectral band, frequency anticorrelations and polarization entanglement. This work is structured in two parts: the implementation of a quantum key distribution protocol with several user pairs, and the implementation of a network connecting each user to all others through a connected graph principle.
In the second part of our project, we wish to explore the frequency-comb structure of the states emitted by our source. We aim at demonstrating that high-dimensional QKD can be used in practice to increase the information throughput and security of these systems, which is useful for a large number of applications.
The project will benefit from the complementarity and recognized expertise of the three partners.
The team of the Quantum Phenomena and Materials (MPQ) Laboratory will contribute with its expertise in semiconductor device modeling and design, integrated non-linear optical device fabrication and characterization, and quantum optics measurements.
The LIP6 Laboratory team will contribute with its know-how on the design and analysis of quantum cryptography protocols in a system and telecom network context.
Nokia Bell Labs will participate in the project through the study and validation of the most relevant technologies for the architecture of a quantum key distribution network, the coherent manipulation of the quantum frequency comb states, and will contribute to the implementation of the test network to validate key distribution experiments.
The project represents an ambitious goal and an important step forward compared to the state of the art in three aspects: technology, system architecture, and quantum key distribution protocols. The results of QUANTIFY will have an impact that goes beyond the objectives of the project and will have immediate applications in the field of quantum communication, information and metrology. The compactness, simplicity and robustness of the systems developed in this project will thus make it possible to take a further step towards the wide diffusion of quantum technologies in real-world applications.