The Department of Physics organises a special seminar with the title

From CERN to quantum engineering: New quantum sensors for photon detection

Speaker: Prof. Stathes Paganis (National Taiwan University)

on Wednesday 4 March 2026 at 12:15 in amphitheatre A31 (School of Natural Sciences).

Abstract: Starting from research at CERN on the Higgs boson, a series of coincidences led us to realize that there are no single-photon detectors in the optical and infrared range capable of simultaneously measuring the number of photons or their energy with high timing precision. In 2025, we proposed a new type of quantum detector: the Dual-Mode SNSPD.

In conventional Geiger mode, the detector operates at temperatures well below the critical temperature T_c, functioning as an event counter without sensitivity to the number of photons incident on the sensor. In calorimetric mode, the detector operates at temperatures just below T_c and exhibits calorimetric sensitivity in the range of 15–250 equivalent absorbed photons for a photon beam with wavelength 515 nm. In this energy-sensitive mode, photon absorption induces Joule heating in the SNSPD.

Depending on the application, by tuning the detector temperature and bias current using the same readout system, the SNSPD can easily switch between the two modes of operation. Beyond providing solutions for spectroscopy and calorimetry applications requiring precise timing and energy resolution, dual-mode SNSPDs can also enable significant advances in high-speed photon-number-resolving detection through their flexible hybrid architecture, fostering innovation in optical quantum computing and the characterization of quantum light sources. These detectors are ideal for dark matter searches as well as for medical imaging applications.

Short CV: I graduated from Aristotle University of Thessaloniki and received my PhD from the University of Texas at Austin in 1999. Immediately afterward, I joined the Columbia University group to work on the ZEUS experiment at HERA. During this period, together with Allen Caldwell (AWAKE) and Frank Sciulli, we designed, constructed, and commissioned the Luminosity Monitor for the upgraded ZEUS experiment. From 1999 to 2003, I served as head of the Luminosity group and of the Structure Function & Electroweak group.

In 2003, I joined ATLAS (University of Wisconsin) and in 2005 moved to the University of Sheffield, UK, where I became Professor in 2014. Within ATLAS, I worked on the LAr electromagnetic calorimeter and in the Higgs group (4l and 2γ channels). After years of TestBeam analyses, I introduced a new calibration scheme for electrons and photons. I provided calibration for both the Barrel and Endcap calorimeters (2004–2008) and contributed several works that led to significant improvements in Higgs boson measurements. On the physics side, I contributed to the original Higgs→4l discovery analysis and to the Higgs→Zγ analysis. I served as the first coordinator of the Higgs→4l analysis (2 years), Higgs→Zγ coordinator (2 years), Physics Analysis Tools coordinator (3 years), and Higgs group validation coordinator (3 years).

In 2014, I joined National Taiwan University (NTU) and the CMS experiment, focusing on a new detector: HGCAL. In CMS, I work on VBF H→γγ, VH→γγ analyses and on searches for exotic diphoton resonances. I have also published several phenomenology-oriented works. From 2015 to 2019, we established a fully operational detector construction laboratory in Taiwan. I am the founder of the Taiwan Instrumentation & Detector Consortium, a center that has produced detectors for CMS, AMS, sPHENIX, STAR at BNL, and in the future for the EIC.

In 2021, I received the Best Physics Researcher Award in Taiwan from the Physical Society of Taiwan, including a monetary prize.

Since January 2022, I have been elected and serve as Chair of the HGCAL Institute Board at CERN. The CMS High Granularity Calorimeter is a €200 million project involving 67 collaborating universities. I work closely with the project managers on financial matters and on all high-level organizational aspects of the project.

Throughout these years, I have also been a fellow of the Taiwan Center for Astrophysics (LeCosPA), where we develop new approaches to research on Dark Matter, Dark Energy, and the Black Hole information loss paradox. This more ambitious line of research led to the proposal of a new type of quantum detector, the dual-mode SNSPD, together with researchers from CEA/Saclay (APL Quantum 2, 026118 (2025)). My current research group includes approximately 25 researchers, students, engineers, and administrative staff.