The project "QUASIX: Single photon integrated source for QUAntum SIlicon Communications in Space" aims to explore and develop quantum technologies for designing energy-efficient and high-performance communication network for space applications. Integrated quantum photonics is an emerging paradigm enabling quantum optics to scale to new heights of purity and security.

Physicists from the Institute of Photonics and Nanotechnologies – Milan, the Department of Physics - Milan Politecnico and the University of Padova work with Sant'Anna School professor Enrico Forestieri (InReTe Lab – TeCIP Institute) on integrated photon source to achieve high-quality single photons. Through a novel technique, scientists aim to build and improve the infrastructure cyber-resilience and cryptographic agility. As current cryptography in communication and information systems need to be adapted in response to future threats, researchers need to address the scaling of integrated quantum photonics while facing errors in quantum computation due to the circuit-increased complexity. As conventional cryptography is based on computational complexity (which might be broken by a powerful quantum computer), quantum cryptographic protocols and quantum key distribution (QKD) can use authenticated and secure communication channels allowing new fault-tolerant quantum machines to solve problems beyond the capability of current supercomputers. 

Quantum computers capable of cryptographic applications are expected in the near future. Within the next five years, researchers will be able to avert security losses and release standard protocols to mitigate the vulnerability of quantum computing. The project QUASIX combines research activity in material science, nano-device physics, processing techniques, photonic IC fabrication technologies, high-end packaging and characterization/validation of prototypes. Thanks to the synergy between the Istituto di Fotonica e Nanotecnologie (IFN) in Milan and the Istituto per la Microelettronica e Microsistemi (IMM) in Catania, advanced nanostructures will be realized by carrying out controlled doping of silicon.

QUASIX uses quantum physics to secure the distribution of symmetric encryption keys. The principles of quantum physics stipulate that observation of a quantum state cause perturbation. QKD protocols are designed to ensure that any attempt by an eavesdropper to observe the transmitted photons will indeed perturb the transmission. This perturbation will lead to transmission errors, which can be detected by the legitimate users to verify the security of the distributed keys.

The QKD - Quantum Key Distribution requires interactions between the users. Interactions need to be authenticated and then combined to be transformed into a secure communication channel. However, transformation imposes strong limitations on the available bandwidth, because the key distribution rate is lower than conventional optical communications. To provide quantum-safe security and expand data rates over the optical infrastructure, the QUASIX research team will leverage the fabrication of integrated devices and components on a single photon source. With the potential to enable a fully qualified space technology, they are committed to providing higher reliability in terms of power consumption and weight, compatibility between optical fiber and air, speed, tolerance to thermal dilation, and room temperature operation.

Cover photo by Gerd Altmann.