Bonn 2025 – scientific programme
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QI: Fachverband Quanteninformation
QI 36: Poster – Quantum Information (joint session QI/Q)
QI 36.44: Poster
Thursday, March 13, 2025, 17:00–19:00, Tent
Characterization and mitigation of optical side-channels in QKD — •Evelyn Edel1, Moritz Birkhold1, 2, Lukas Knips1,2,3, Sebastian Melik4, and Harald Weinfurter1,2,3 — 1Ludwig Maximilian University, Munich, Germany — 2Munich Center for Quantum Science and Technology, Munich, Germany — 3Max Planck Institute of Quantum Optics, Garching, Germany — 4University of Gdańsk, Gdańsk, Poland
Unlike classical key distribution methods reliant on computationally hard problems, quantum key distribution (QKD) achieves information-theoretic security by the principles of quantum mechanics. The decoy-state BB84 protocol offers a practical scheme for realizing free-space QKD sender modules, allowing the use of highly attenuated laser pulses as a photon source. Yet, device imperfections could make side channel attacks by an eavesdropper possible. This work presents a characterization of spectral side channels in our sender module, arising from imperfect spectral overlap. For pulse generation, the module under investigation hosts four vertical-cavity surface-emitting lasers (VCSELs) in a monolithic array, one for each polarization state. Using a spectrometer also in combination with a streak camera, we analyze the spectral behavior and time-dependent variations of these diodes for different bias and modulation currents. To minimize the resulting side channels, Peltier modules are tested for cooling individual diodes. This setup will allow us to identify VCSEL arrays with the best spectral overlaps and quantize the information leaked to an eavesdropper, facilitating the future optimization of our modules.
Keywords: QKD; Quantum Key Distribution; BB84; Satellite-based Quantum Communication