Quantum Mechanics has revolutionized not only our understanding of Nature but also, being the foundation of electronics and lasers, virtually all the instruments we use every day. Then again, we have not yet been able to harness the consequences of the most profoundly quantum phenomena such as state superpositions and particle entanglement. The Second Quantum Revolution has the ambition of building novel "quantum machines" able to fully exploit the properties of both microscopic and macroscopic quantum states.

Quantum sensors, making use of the phenomenon of entanglement in systems promise to reach the fundamental measurement limits determined by the laws of physics and correspondingly improve the current performance of the sensors by orders of magnitude in terms of precision and accuracy, with important application implications in the scientific, industrial, and commercial fields. They can measure with unprecedented precision a wide class of physical quantities, such as magnetic, electric, and inertial fields, times, frequencies, temperatures and pressures.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

Position, navigation, and time (PNT) distributed by the global navigation satellite system (GNSS) have become one of the most relied upon commodities of our civilization. GNSS relies on clocks on satellite, the timing signal of which is send to Earth. On ground both, the resulting position and the timing signal are used in various different cases on ground. We are reliant on the quality of the timing signal.

Quantum technologies offer novel methods of probing atoms or molecules to generate timing signals of higher quality. Additionally, optical cavities or resonators can provide precise timing signals. The main challenge involved with optical resonators is the long term stability in compatibility with the SWaP requirements of space. There are several works to prolong the stability of these systems and improve the quality of the received signal. Regardless of the quality of the GNSS signal, it is subject to manipulation, such as jamming and spoofing. Additionally, areas of absence of GNSS exist, which need to be breached. In these cases (classical) inertial measurement units can be deployed. However, the inherent drift of these systems allow GNSS-free navigation for short periods.

Quantum radars allow to enhance performances of conventional systems by exploiting high order correlations between entangled states of light using quantum illumination protocols. Such systems can be used for short mid-range applications such as unmanned aerial system (UAS) detection or target detection in degraded visual environments (DVE).

In this work we present computational simulations of receiver operating characteristic (ROC) curves of a binary classifier system implementing quantum and classical resources for real case applications comparing benefits and drawbacks given current technological capabilities.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

It has been demonstrated that time-correlated single-photon counting (TCSPC) has the potential to be the preferred choice of detection for high resolution three-dimensional profiling in several challenging scenarios, for example through obscurants and complex multiple surface targets. Over the last few years, the TCSPC technique has been used in highly scattering underwater environments, demonstrating submillimeter resolution in turbid environments with over 8 attenuation lengths between transceiver and target due to its excellent surface to surface resolution and high optical sensitivity. This presentation will describe several transceiver systems for underwater imaging based on a range of silicon single photon avalanche diode (Si-SPAD) detectors, either fabricated in custom planar fabrication technology and in complementary metal-oxide semiconductor (CMOS) technology. Laboratory based experiments and field trials were conducted in several scattering underwater environments, demonstrating imaging up to 9.2 attenuation lengths and ranging up to 14 attenuation lengths when using average optical power up to 50 mW.

The resolution of optical systems, formulated as the smallest possible distance between two point sources for which they still can be dissolved, was for a long time believed to be limited by diffraction, formulated by the Rayleigh criterion. Recent advancements in quantum metrology have shown, by evaluation of the Quantum Cramér Rao bound (QCRB), that the Rayleigh criterion is not a fundamental limit. In our experiment, spatial mode demultiplexing (SPADE) is used to estimate the separation of the sources orders of magnitude below the Rayleigh limit. The experiment is extended to incorporate the measurement of additional parameters, such as power imbalance and centroid position of the two sources, bringing it closer to real-world applicability.

The problem of resolving pointlike light sources not only serves as a benchmark for optical resolution but also holds various practical applications ranging from microscopy to astronomy. In this study, we aim to resolve two thermal sources sharing arbitrary mutual coherence using the spatial mode demultiplexing technique. Our analytical moment-based approach covers scenarios where the coherence and the emission rate of the sources depend on the separation between them, and is not limited to the Poissonian approximation. Studying the examples of the interactive dipoles imaging and imaging of the reflective particles under external illumination, we demonstrate that separation-dependent coherence, which arises in this scenario, can significantly enhance optical resolution. We show that this effect is robust in the presence of the emitters dephasing and detection noise.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

Due to their high sensitivity, wide frequency range, SI-traceability and reduced size at low frequency, Rydberg atoms based- sensors of RF/THz fields hold great prospects for many applications including telecommunications, radar, and THz imaging. So far, almost all of these sensors have consisted in probing by means of EIT spectroscopy the Autler-Townes effect resulting from the interaction between the field and a warm vapor of alkaline Rydberg atoms. Despite significant improvement using heterodyning, this approach suffers several limitations caused by broadening mechanisms inherent to warm vapors, and by using EIT as a probe. We report here on a new approach based on trap-loss spectroscopy of the Autler-Townes effect in cold 87Rb atoms confined in a MOT. The doublet of dressed Rydberg states measured this way obeys well the theoretical model of Autler-Townes effect provided lightshifts from neighboring Rydberg states are considered, suggesting the possibility to infer the characteristics of the field from those of the doublet. Study of the resulting sensor revealed a very good linearity, with residual errors of 1%, and a resolution of 5 µV/cm after an integration time of 2600s.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

Photonic quantum computers offer great potential for defence and security due to their room temperature operation and integrability. However, to best exploit such platforms, it is required to program any algorithm in specific frameworks like measurement-based quantum computing or boson sampling. We show how to use both frameworks, for specific tasks and problems relevant to industry.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

This conference presentation was prepared for SPIE Sensors + Imaging 2024.

Quantum key distribution (QKD) is the quantum technology aimed at distributing secret keys with the provable security, based on the principles of quantum physics. After having been implemented in the point-to-point scenarios between two trusted parties, QKD shall be extended to multi-user networks to increase its efficiency and scalability. The existing solutions for quantum networking rely on probabilistic or time-sharing strategies. We propose continuous-variable quantum passive-optical-network (CV-QPON) based on quadrature modulation, passive optical network and homodyne detection of coherent states, enabling deterministic and simultaneous secret key generation among all network users. We demonstrate key generation between 8 users, each with an 11 km span of access link. Depending on the trust assumptions about users, we report up to 2.1 Mbits/s of total network key generation. The proposed CV-QPON protocols offer a pathway toward low-cost, high-rate, and scalable quantum access networks using standard telecom techniques.