# Publications

###### Architectural Modeling and Experimental Characterization of SPAD-based Imager developed for Fast-Quantum Ghost Imaging Applications

E. Manuzzato, M. Gandola, M. Perenzoni, L. Gasparini, and R. Passerone

submitted in JUNE 2024: SIE 2024 (to be published at LNEE)

Quantum Ghost Imaging (QGI) uses quantum light proper-ties to investigate biological samples. It involves a single quantum source generating two beams: a visible signal beam detected by an image sensor and an idler beam with sample information detected by a single-channel bucket detector. Temporal correlations between these two detectors are exploited to create a ghost image of the sample at the target wavelength…

###### Off-axis holographic imaging with undetected light

J.R. León-Torres, F. Krajinić, M. Kumar, M. Gilaberte Basset, F. Setzpfandt, V.F. Gili, B. Jelenković, and M. Gräfe

submitted APR 26, 2024: arXiv:2404.17370v1 [physics.optics];

Quantum imaging with undetected light (QIUL) can retrieve amplitude and phase information of an object by exploiting the quantum correlations of photon-pairs generated through spontaneous parametric down conversion (SPDC), where the illumination and detection can be carried at very distinct wavelength ranges. This fact allows to benefit from a mature detection technology in the visible spectral range, while probing the object at a more exotic wavelength. Here we experimentally implement a QIUL approach with Fourier off-axis holography…

###### Quantum Estimation of the Stokes Vector Rotation for a General Polarimetric Transformation

A. Pedram, V.R. Besaga, L. Gassab, F. Setzpfandt, and Ö.E. Müstecaplıoğlu

submitted APR 25, 2024: arXiv:2304.08258v2 [quant.phys];

Classical polarimetry is a well-established discipline with diverse applications across different branches of science. The burgeoning interest in leveraging quantum resources to achieve highly sensitive measurements has spurred researchers to elucidate the behavior of polarized light within a quantum mechanical framework, thereby fostering the development of a quantum theory of polarimetry. In this work, drawing inspiration from polarimetric investigations in biological tissues, …

###### Nonlocality Enhanced Precision in Quantum Polarimetry via Entangled Photons

A. Pedram, V.R. Besaga, F. Setzpfandt, and Ö.E. Müstecaplıoğlu

submitted FEB 19, 2024: Adv Quantum Technol. (2024), 2400059; DOI 10.1002/qute.202400059

A nonlocal quantum approach is presented to polarimetry, leveraging the phenomenon of entanglement in photon pairs to enhance the precision in sample property determination. By employing two distinct channels, one containing the sample of interest and the other serving as a reference, the conditions are explored under which the inherent correlation between entangled photons can increase measurement sensitivity. Specifically, the quantum Fisher information (QFI)…

###### Generation of infrared photon pairs by spontaneous four-wave mixing in a CS2-filled microstructured optical fiber

M. Afsharnia, S. Junaid, S. Saravi, M. Chemnitz, K. Wondraczek, T. Pertsch, M.A. Schmidt, and F. Setzpfandt

submitted OCT 27, 2023: Sci. Rep. **14**, 977 (2024): DOI 10.1038/s41598-024-51482-0

We experimentally demonstrate frequency non-degenerate photon-pair generation via spontaneous four-wave mixing from a novel CS2-filled microstructured optical fiber. CS2 has high nonlinearity, narrow Raman lines, a broad transmission spectrum, and also has a large index contrast with the microstructured silica fiber. We can achieve phase matching over a large spectral range by tuning the pump wavelength, allowing the generation of idler photons in the infrared region, which is suitable for applications in quantum spectroscopy…

###### A 100×100 CMOS SPAD Array with In-Pixel Correlation Techniques for Fast Quantum Ghost Imaging Applications

M. Gandola, E. Manuzzato, M. Perenzoni, F. Dal Farra, V.F. Gili, D. Dupish, A. Vega, T. Pertsch, F. Setzpfandt, and L. Gasparini**ESSCIRC 2023**– IEEE 49th European Solid State Circuits Conference (ESSCIRC), Lisbon, Portugal, 105-108 (2023): DOI 10.1109/ESSCIRC59616.2023.10268722

In this paper, a 100×100 CMOS Single Photon Avalanche Diode (SPAD) array designed for quantum imaging applications requiring synchronization with an external unpredictable and aperiodic trigger is presented. The targeted application takes advantage of non-classical quantum states of light to achieve quantum ghost imaging in the middle-infrared (MIR) up to 7 μm wavelength by detecting the corresponding entangled photons in the visible spectrum with the SPAD imager…

###### SPOOKY IMAGING FOR BIOMEDICAL SENSING

1st Public Workshop · JUN 28, 2023

- Dr. Valerio Flavio Gili · Fraunhofer IOF:
**Introducing FastGhost** - Dr. Mario Castaneda · Single Quantum BV :
**Single-pixel Detector** - Dr. Massimo Gandola · Fondazione Bruno Kessler:
**SPAD Array**

Forum World of Quantum 2023

Chair: Dr. Stephanie Hesse-Ertelt · Fraunhofer IOF

The FastGhost consortium of partners Fondazione Bruno Kessler, Single Quantum BV, Fraunhofer IOF, Friedrich-Schiller-Universität Jena, and Kungliga Tekniska Hoegskolan aims to move the scheme of ghost imaging from academic curiosity towards applications by extending the spectral range into the mid-infrared and by making it run on a scanning microscope system. The latest results and achievements from the FastGhost project will be presented and discussed…

###### Experimental analysis on image resolution of quantum imaging with undetected light through position correlations

M. Gilaberte Basset, R. Sondenheimer, J. Fuenzalida, A. Vega, S. Töpfer, E.A. Santos, S., F. Setzpfandt, F. Steinlechner, and M. Gräfe

submitted JUN 02, 2023: arXiv:2306.01884 [quant-ph]; Phys. Rev. **A108**, 052610 (2023): DOI 10.1103/PhysRevA.108.052610

Image resolution of quantum imaging with undetected photons is governed by the spatial correlations existing between the photons of a photon pair that has been generated in a nonlinear process. These correlations allow for obtaining an image of an object with light that never interacted with that object. Depending on the imaging configuration, either position or momentum correlations are exploited. We hereby experimentally analyse how the crystal length and pump waist affect the image resolution when using position correlations of photons that have been generated via spontaneous…

###### SUB-MINUTE QUANTUM GHOST IMAGING IN THE INFRARED ENABLED BY A „LOOKING BACK“ SPAD ARRAY

V.F. Gili, D. Dupish, A. Vega, M. Gandola, E. Manuzzato, M. Perenzoni, L. Gasparini, T. Pertsch, and F. Setzpfandt

submitted NOV 23, 2022: arXiv:2211.12913v1 [physics.optics];

Applied Optics **62/12**, 3093 (2023): DOI 10.1364/AO.487084

Quantum Ghost Imaging (QGI) is an intriguing imaging protocol that exploits photon-pair correlations stemming from spontaneous parametric down-conversion (SPDC). QGI retrieves images from two-path joint measurements, where single-path detection does not allow to reconstruct the target image. This technique, has been so far limited in terms of acquisition speed either by raster scanning, or by the slow electronics of intensified cameras. Here we report on a fast QGI implementation exploiting a SPAD array detector…

###### 2023 roadmap for materials for quantum technologies

C. Becher, W. Gao, S. Kar, C. Marciniak, T. Monz,

J.G. Bartholomew, P. Goldner, H. Loh, E. Marcellina, K.E.J. Goh, T.S. Koh, B. Weber, Z. Mu, J.-Y. Tsai, Q. Yan, S. Gyger, S. Steinhauer, V. Zwiller

submitted NOV 17, 2022: Mater. Quantum. Technol. **3**, 012501 (2023): DOI 10.1088/2633-4356/aca3f2

Quantum technologies are poised to move the foundational principles of quantum physics to the forefront of applications. This roadmap identifies some of the key challenges and provides insights on materials innovations underlying a range of exciting quantum technology frontiers. Over the past decades, hardware platforms enabling different quantum technologies have reached varying levels of maturity. This has allowed for first proof-of-principle demonstrations of quantum supremacy, …

###### Spectral tailoring of photon pairs from microstructured suspended-core optical fibers with liquid-filled nanochannels

M. Afsharnia, Z. Lyu, T. Pertsch, M.A. Schmidt, S. Saravi, and F. Setzpfandt

submitted APR 25, 2022: Optics Express **30/16**, 29680 (2022):

DOI 0.1364/OE.461331

We theoretically study the generation of photon pairs via spontaneous four-wave mixing (SFWM) in a liquid-filled microstructured suspended-core optical fiber. We show that it is possible to control the wavelength, group velocity, and bandwidths of the two-photon states. Our proposed fiber structure shows a large number of degrees of freedom to engineer the two-photon state. Here, we focus on the factorable state, which shows no spectral correlation in the two-photon components of the state, and allows the heralding…

###### Experimental realization of scanning quantum microscopy

V.F. Gili, C. Piccinini, M. Safari Arabi, P. Kumar, V. Besaga, E. Brambila, M. Gräfe, T. Pertsch, and F. Setzpfandt

submitted APR 14, 2022: Appl. Phys. Lett. **121**, 104002 (2022): DOI 10.1063/5.0095972

Quantum imaging is an ever expanding research field in which the aim is to exploit the quantum nature of light to enhance image reconstruction capabilities. Despite a number of successful demonstrations for quantum imaging, quantum microscopy still seems out of the range for practical applications due to different physical and technical reasons. Here, we propose an imaging method exploiting the quantum correlations of photon pairs and a scanning microscope to achieve fast, single mode quantum imaging. We first test our technique on a metal grating to estimate the resolution capabilities of our system. Moreover, …

###### Fundamental resolution limit of quantum imaging with undetected photons

A. Vega, E.A. Santos, J. Fuenzalida, M. Gilaberte Basset, T. Pertsch, M. Gräfe, S. Saravi, and F. Setzpfandt

submitted MAR 11, 2022: Phys. Rev. Res. **4**, 033252 (2022):

DOI: 10.1103/PhysRevResearch.4.033252

Quantum imaging with undetected photons relies on the principle of induced coherence without induced emission and uses two sources of photon pairs with a signal- and an idler photon. Each pair shares strong quantum correlations in both position and momentum, which allows us to image an object illuminated with idler photons by just measuring signal photons that never interact with the object. In this work, we theoretically investigate the transverse resolution of this nonlocal imaging scheme through a general formalism that treats propagating photons beyond the commonly used paraxial approximation. …

###### 2022 roadmap for materials for quantum technologies

C. Becher, W. Gao, S. Kar, C. Marciniak, T. Monz,

J.G. Bartholomew, P. Goldner, H. Loh, E. Marcellina, K.E.J. Goh, T.S. Koh, B. Weber, Z. Mu, J.-Y. Tsai, Q. Yan, S. Gyger, S. Steinhauer, V. Zwiller

submitted FEB 15, 2022: arXiv:2202.07309 [quant-ph]

Quantum technologies are poised to move the foundational principles of quantum physics to the forefront of applications. This roadmap identifies some of the key challenges and provides insights on materials innovations underlying a range of exciting quantum technology frontiers. Over the past decades, hardware platforms enabling different quantum technologies have reached varying levels of maturity. This has allowed for first proof-of-principle demonstrations of quantum supremacy, for example quantum computers surpassing their classical counterparts, quantum communication with reliable security…

###### Current Crowding in Nanoscale Superconductors within the Ginzburg-Landau Model

M. Jönsson, R. Vedin, S. Gyger, J.A. Sutton, S. Steinhauer, V. Zwiller, M. Wallin, and J. Lidmar

submitted DEC 10, 2021: Phys. Rev. Applied **17**, 064046 (2022): DOI 10.1103/PhysRevApplied.17.064046

The current density in a superconductor with turnarounds or constrictions is nonuniform due to a geometrical current-crowding effect. This effect reduces the critical current in the superconducting structure compared to a straight segment and is of importance when designing superconducting devices. We investigate the current-crowding effect in numerical simulations within the generalized time-dependent Ginzburg-Landau (GTDGL) model. The results are validated experimentally by measuring the magnetic field dependence…

###### MID-INFRARED PHOTON-PAIR GENERATION IN AGGAS2

M. Kumar, P. Kumar, A. Vega, M. A. Weissflog, T. Pertsch, and F. Setzpfandt

submitted OCT 04, 2021: arXiv:2110.01511v2 [physics.optics];

Appl. Phys. Lett. **119**, 244001 (2021): DOI 10.1063/5.0074054

We demonstrate non-degenerate photon-pair generation by spontaneous parametric down conversion in a silver gallium sulfide AgGaS2 crystal. By tuning the pump wavelength, we achieve phase matching over a large spectral range. This allows to generate idler photons in the mid-infrared spectral range above 6 μm wavelength with corresponding signal photons in the visible. Also, we show photon pair generation with broad spectral bandwidth. These results are a valuable step towards the development of quantum imaging and sensing techniques in the mid-infrared.

###### Efficient mid-infrared single-photon detection using superconducting NbTiN nanowires with high time resolution in a Gifford-McMahon cryocooler

J.Chang, J.W.N. Los, R. Gourgues, S. Steinhauer, S.N. Dorenbos, S.F. Pereira, H.P. Urbach, V. Zwiller, and I.E. Zadeh

submitted JUL 13, 2021: arXiv:2107.06354v1 [physics.ins-det];

Photonics Research **10/4**, 1063 (2022): DOI 10.1364/PRJ.437834

Shortly after their inception, superconducting nanowire single-photon detectors (SNSPDs) became the leading quantum light detection technology. With the capability of detecting single-photons with near-unity efficiency, high time resolution, low dark count rate, and fast recovery time, SNSPDs outperform conventional single-photon detection techniques. However, detecting lower energy single photons ( <0.8 eV) with high efficiency and low timing jitter has remained a challenge…

###### Quantum holography with undetected light

S. Töpfer, M. Gilaberte Basset, J. Fuenzalida, F. Steinlechner, J. P. Torres, M. Gräfe

submitted JUN 09, 2021: arXiv:2106.04904v3 [quant-ph];

Sci. Adv. **8**, eabl4301 (2022): DOI 10.1126/sciadv.abl4301

Holography exploits the interference of light fields to obtain a systematic reconstruction of the light fields wavefronts. Classical holography techniques have been very successful in diverse areas such as microscopy, manufacturing technology, and basic science. Extending holographic methods to the level of single photons has been proven challenging, since applying classical holography techniques to this regime pose technical problems. Recently the retrieval of the spatial structure of a single photon, using another photon under experimental control with a well-characterized spatial shape as reference, was demonstrated…

###### Classical Ghost Imaging: A Comparative Study of Algorithmic Performances for Image Reconstruction in Prospect of Plenoptic Imaging

M. Braasch, V.F. Gili, T. Pertsch, and F. Setzpfand

submitted MAY 13, 2021: IEEE Photonics Journal **13/3**, 6800914 (2021): DOI 10.1109/JPHOT.2021.3087753

Ghost Imaging has been extensively explored for 25 years for a two reasons: the rich physics of second-order photon correlations that enable this imaging scheme and the possibility of implementing new imaging protocols with interesting real-life applications, e.g. imaging in turbulent media, investigation of sensitive samples in low-flux regimes, 3-D plenoptic imaging, and so on. Since the first demonstration of Ghost Imaging, several extended versions of the Traditional Ghost Imaging algorithm have been proposed…

###### Superconducting nanowire single-photon detectors: A perspective on evolution, state-of-the-art, future developments, and applications

I.E. Zadeh, J. Chang, J.W.N. Los, S. Gyger, A.W. Elshaari, S. Steinhauer, S.N. Dorenbos, and V. Zwiller

submitted JAN 31, 2021: Appl. Phys. Lett. **118**, 190502 (2021): DOI 10.1063/5.0045990

Two decades after their demonstration, superconducting nanowire single-photon detectors (SNSPDs) have become indispensable tools for quantum photonics as well as for many other photon-starved applications. This invention has not only led to a burgeoning academic field with a wide range of applications but also triggered industrial efforts. Current state-of-the-art SNSPDs combine near-unity detection efficiency over a wide spectral range, low dark counts, short dead times, and…