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QI: Fachverband Quanteninformation
QI 11: Implementations IV
QI 11.7: Vortrag
Mittwoch, 11. März 2026, 11:45–12:00, BEY/0245
A charge-basis tomographic protocol for superconducting qubits — •Elena Lupo1, Daniel Long2, Daniel Dahan3, Konstantin Yavilberg3, Malcolm R. Connolly2, Eytan Grosfeld3, and Eran Ginossar4 — 1Forschungszentrum Jülich, 52428 Jülich, Germany — 2Imperial College London, SW7 2AZ London, UK — 3Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel — 4University of Surrey, GU2 7XH Guildford, UK
The use of accurate models and parameters in superconducting circuits is essential for the understanding and control of quantum states. While conventional spectroscopic techniques allow the extraction of excited-state populations, transition frequencies, and decay rates, information about quantum coherence can only be obtained through phase-sensitive methods such as quantum state tomography, which is usually performed in the system's energy basis. Here we introduce a complementary tomographic protocol for the reconstruction of the ground state of a superconducting circuit with a generic Josephson junction potential [1]. The state reconstruction is done in the basis of its relative charge across the junction - a representation that can provide new insights into the quantum circuit and can assist in validating its Hamiltonian model. The method combines the flux-tuning of a split Josephson junction and adiabatic evolution to achieve the desired density matrix reconstruction of the circuit's ground state. Further possible applications of this method include the study of hybrid superconductor-semiconductor junctions [2]. [1] Lupo et al, arXiv: 2502.07748; [2] Dahan et al, arXiv: 2502.07684.
Keywords: Quantum state tomography; superconducting circuit; charge-basis tomography