Tuesday 4:30 pm (Freiburg) / 7:30 am (Vancouver)
14.04.26 – Merline Cherukarathadathil Ulahannan
(University of Freiburg)
21.04.26 – Maria Popovic (University of Milan, Italy)
28.04.26 – Alexie Boyer (University of Strasbourg, France)
05.05.26 – Krzysztof Jachymski (University of Warsaw, Poland)
12.05.26 – Martin Pichotka (University of Freiburg)
19.05.26 – Manuel Gessner (University of Valencia, Spain)
02.06.26 – Frank Schlawin (University of Hamburg)
16.06.26 – Iva Brezinova (TU Vienna, Austria)
23.06.26 – Peter Ratzikis (IESL-FORTH, Greece)
30.06.26 – Madhusree Roy-Chowdhury (University of Kassel)
14.07.26 – Nicolas Treps (Sorbonne University, France)
21.04.26 – Maria Popovic (University of Milan, Italy)
Multiparameter quantum estimation of circulant graphs
In multiparameter estimation, compatibility conditions and Cramér-Rao bounds dictate the loss of information on individual parameters and the limits on estimation precision, while few systems allow for a fully analytical approach. Here, we present the analytical derivation of precision limits for the simultaneous estimation of vertex coupling strengths in circulant graphs, probed by the continuous-time quantum walk of a particle. We demonstrate that the weak compatibility condition is always satisfied, and show instances for which the estimations of the individual parameters are statistically independent. We analyse the classical Cramér-Rao bound derived from position measurements on the quantum walker, and evaluate how measurement time and experimental limitations – such as coarse-grained measurements – affect the estimation efficiency for two couplings. Furthermore, we derive the optimal initial states of the probe that achieve best estimation precision. Our findings highlight the role of graph symmetry in saturating multiparameter estimation precision bounds, and establish a benchmark for quantum metrology in networked systems.
Chair: Alessandra Colla
14.04.26 – Merline Cherukarathadathil Ulahannan (University of Freiburg)
Design for a Monochromatic, High-Repetition-Rate XUV Beamline for Time-Resolved Photoelectron–Photoion Coincidence Spectroscopy
In the first part of this talk, I will present my Master’s project carried out at TIFR Hyderabad, where I worked on building a laser-driven X-ray diffraction apparatus. Using a kHz femtosecond Ti:Sapphire laser (800 nm, 25 fs, 2.5 mJ, 1 kHz) focused onto a 20 μm methanol jet in vacuum, I generated a hot dense plasma producing highly energetic electrons (~2 MeV). The resulting highly energetic electrons was used for generating X-rays (~8 keV) which we tried to use for XRD.
In the next section I present our plans for a monochromatic XUV beamline with high-repetition rates of up to 120 kHz for time-resolved photoelectron photoion coincidence spectroscopy. The beamline will be based on a cascaded harmonic generation scheme [1] driven by an Yb Laser. The 800 μJ near IR pulses will be first spectrally broadened by self-phase modulation in a gas-filled multipass cell and compressed to ~40, after which the pulse is passed through a BBO crystal to generate the second harmonic (515 nm). The resulting pulses will be used to efficiently drive the HHG process in a gas jet producing XUV radiation in the range between 10 and 20 eV. After separation of the XUV from the driving field we will use a time-preserving monochromator [2] with a single plane diffraction grating in off-plane geometry for spectral selection while maintaining pulse durations of tens of femtoseconds.
A home-built nonlinear optical parametric amplifier pumped by the same Yb Laser will supply frequency-tunable ultrashort pump pulses in the visible and UV spectral range. This beamline will be used in performing time-resolved XUV photoelectron–photoion coincidence spectroscopy in molecular complexes.
References:
- Comby et al., Opt. Express 27, 20383 (2019).
- Frassetto et al., Opt. Express 19, 19169 (2011).
Chair: Sebastian Hartweg
