arXiv subjects

Gianluca De Santis

Publications and source records attributed to Gianluca De Santis.

6 recordsLinked to original sources

arXiv2026

Terrestrial readiness campaign for space-to-ground quantum communications with a space-qualified entangled photon-pair system

Realizing a global quantum internet relies on the deployment of robust satellite-based entanglement distribution links. While pioneering demonstrations have established the feasibility of such links, the transition to operational infrastructure demands the validation of robust, integrated space-to-ground architectures. Here, we report on a free-space Quantum Key Distribution experiment conducted over a 1.8 km free-space link using an engineering model of the quantum payload onboard the SpeQtre satellite and the Abu Dhabi Quantum Optical Ground Station. By implementing a BBM92 protocol with polarization-entangled photons, a secret key rate of approximately 7.56 kbps with a mean quantum bit error rate of 4.78%+-0.24% was produced. The deployed system featured spectral and spatial filtering approaches identical to those in the space segment, thus validating the link budget and background rejection capabilities under realistic atmospheric conditions. These results confirm the operational compatibility between the ground and space segments, establishing a critical performance baseline for the SpeQtre mission and future space-based, large-scale quantum networks.

quant-ph↗

arXiv2025

Quantum Random Number Generator with Internal Consistency Check and Public Verification

Quantum Random Number Generators provide true physical randomness based on quantum processes, essential for cryptographic and scientific applications. However, practical implementations face challenges in robustness and verifiability: ensuring that the entropy source remains secure and stable over time, and enabling independent confirmation of randomness quality without compromising security. We present a system based on a simple looped beam splitter architecture that uses only passive optical components. The device features an intrinsic self-testing mechanism derived from the stability of detection-probability ratios, allowing continuous validation of correct operation. In addition, the same physical process generates two independent random sequences with identical entropy: a private sequence, used for secure applications, and a public one, enabling external statistical verification with zero mutual information between them. This approach demonstrates that robust, self-testing, and publicly verifiable quantum randomness can be achieved with minimal optical complexity without jeopardizing security.

quant-ph↗

arXiv2025

Impact of polarization mode dispersion on entangled photon distribution

Polarization mode dispersion (PMD) in optical fibers poses a major challenge for maintaining the fidelity of quantum states for quantum communications. In this work, a comprehensive model linking the probability of quantum measurement errors (infidelity) to PMD is developed and validated by experimental measurements of differential group delay and quantum bit error rate (QBER). Our research proposes effective methods to mitigate PMD effects for broadband entangled photons and evaluates the impact of higher-order PMD effects. The model provides an experimentally verified framework for the optimization of commercial quantum key distribution systems in deployed fiber optic lines.

quant-ph↗

arXiv2024

Versatile Optical Ground Station for Satellite-based Quantum Key Distribution in Abu Dhabi

With the growing number of satellite-based Quantum Key Distribution (QKD) payload launches, it becomes essential to ensure compatibility across different platforms for satellite tracking and quantum signal acquisition. In this paper, the Technology Innovation Institute (TII) presents the development of the Abu Dhabi Quantum Optical Ground Station (ADQOGS) for secure free-space optical communications. With the know-how of GA-Synopta's experienced engineering team, we have developed a versatile multi-wavelength quantum acquisition and tracking system tailored to support various upcoming space-based QKD missions, crucial for the practical implementation of global quantum communication networks. This system is capable of handling multiple wavelengths, ranging from 600 nm to 1560 nm for downlink beacons and 1530 nm to 1610 nm for uplink beacons. It includes a free-space quantum module adequate to detect QKD signals at $780\pm10$ nm and $850\pm3$ nm and offers spatial and spectral filtering capabilities along with a motorized polarization correction system.

quant-ph↗

arXiv2024

Parallel trusted node approach for satellite quantum key distribution

Quantum key distribution (QKD) via satellite links is the only currently viable solution to create quantum-backed secure communication at a global scale. To achieve intercontinental coverage with available technology one must adopt a "flying trusted node" paradigm, in which users fully trust the satellite platform. Here, inspired by the concept of distributed secret sharing and the imminent projected launch of several QKD-equipped satellites, we propose a parallel trusted node approach, in which key distribution is mediated by several satellites in parallel. This has the effect of distributing the trust, removing single points of failure and reducing the necessary assumptions. In addition, we discuss the versatility that an optical ground station should provide to execute such a protocol and, in general, to be fully integrated into a multi-party global quantum network.

quant-ph↗

arXiv2023

Generation and characterization of polarization-entangled states using quantum dot single-photon sources

Single-photon sources based on semiconductor quantum dots find several applications in quantum information processing due to their high single-photon indistinguishability, on-demand generation, and low multiphoton emission. In this context, the generation of entangled photons represents a challenging task with a possible solution relying on the interference in probabilistic gates of identical photons emitted at different pulses from the same source. In this work, we implement this approach via a simple and compact design that generates entangled photon pairs in the polarization degree of freedom. We operate the proposed platform with single photons produced through two different pumping schemes, the resonant excited one and the longitudinal-acoustic phonon-assisted configuration. We then characterize the produced entangled two-photon states by developing a complete model taking into account relevant experimental parameters, such as the second-order correlation function and the Hong-Ou-Mandel visibility. Our source shows long-term stability and high quality of the generated entangled states, thus constituting a reliable building block for optical quantum technologies.

quant-ph↗