Quantum Sensing is a rapidly growing branch of research within the area of quantum science and technology offering key resources, beyond classical ones, with clear potential for realization of novel (quantum) sensors. The activity of our lab is focused on the exploitation of quantum resources offered by photons to boost the performance of novel quantum sensors, drawing an innovative programme of challenging applications. We are building on the idea of the Quantum Ghost Spectroscopy (QGS), i.e. the counterpart in the frequency domain of Quantum Ghost Imaging (QGI), and we are addressing challenges in basic research, targeting novel applications. Ghost imaging (GI) is a sophisticated method to image an object without analysing the light that passed through it and the framework of QGI extends such possibility to the quantum domain usually through the use of spatial quantum correlations of photon pairs generated via Spontaneous Parametric Down Conversion (SPDC). However, focusing on spatial correlations only is quite restrictive, as such corre lations can be in the spectral or polarization domain as well, and the analysis of one of the correlated photons provides information on what has occurred to its twin. Therefore, if the SPDC source generates pairs of photons in a nondegenerate configuration, i.e. belonging to different wavelength ranges (the first in the VIS and the second in the IR range), it could be possible to link IR and VIS components of the emission in such a way that spectral information in the former range can be assessed by looking only at the latter. This means that the requirements for accurate measurements are shifted from the IR to the VIS domain, for which much more solid, reliable and cost-effective solutions are available. Hence, the time-frequency domain reveals a huge potential for several applications and frequency correlations represent a versatile tool that can be exploited to enable the spectral analysis of objects where a direct measurement would not be feasible (e.g. security). This approach has been employed for the detection of several possible harmful threats showing optical properties in the NIR spectral regions. Classical and quantum schemes have been compared assessing the metrological advantage achievable by the second approach [1]. It has been demonstrated also that it is possible to reveal the presence of a target fast and accurately by comparing a low resources measurement with a reference [2]. By suitably adapting the implemented approach we were able to unify QGS and QGI and to obtain more information from a single measurement [3] demonstrating that it could be possible to reveal spectral features of the target and to localize it.
This work paves the way to future developments based on a multi-degrees of freedom approach towards the hyperspectral quantum ghost imaging. The use of a nondegenerate source has allowed us also to build and test a quantum spectrometer working in the NIR wavelengths employing the usual detectors for the visible region, showing the effectiveness of this technique with several different samples [4]
The QGS has also been exploited to explore the impact of white and colored noise on quantum correlations [5]. The obtained results reveal that quantum correlations remain robust in the presence of white noise, whereas colored noise has a detrimental effect. This work represents an important advancement in the effective and efficient adoption of quantum correlations in quantum-based protocols and provides a valuable insight into the resilience of quantum correlations—central to all quantum protocols.
[1] A. Chiuri, et al., Ghost imaging as loss estimation: Quantum versus classical schemes, Phys. Rev. A 105 (2022)
[2] A. Chiuri, et al., Fast remote spectral discrimination through ghost spectrometry, Phys. Rev. A 109 (2024)
[3] A. Chiuri, et al., Quantum Ghost Imaging Spectrometer, ACS Photonics 10 (2023)
[4] A. Chiuri, et al., Near Infrared Quantum Ghost Spectroscopy for Threats Detection, Eur. Phys. J. Plus (2025) 140: 186 (2025)
[5] L. Sansoni, et al., An experimental investigation of quantum frequency correlations resilience against white and colored noise, https://doi. org/10.48550/arXiv.2503.16314 (2025)