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QI: Fachverband Quanteninformation

QI 17: Decoherence and Open Systems II

QI 17.5: Vortrag

Donnerstag, 12. März 2026, 16:00–16:15, BEY/0137

Exceptional Points and Optimized Encoding under Continuous Measurement — •Yves Rottstaedt¹, Andrei Pavlov², Alexander Shnirman², Yuval Gefen³, and Bernd Rosenow¹ — ¹Universität Leipzig, Leipzig, Germany — ²Karlsruhe Institut für Technologie, Karlsruhe, Germany — ³Weizmann Institute of Science, Rechovot, Israel

We study a system of three qubits subject to blind continuous stabilizer measurements and stochastic bit-flip errors. The resulting open-system dynamics are governed by a non-Hermitian Liouvillian superoperator, which exhibits an exceptional point (EP) at a specific critical error rate: two eigenvalues coalesce and their eigenmodes merge into a single vector, forming a nontrivial Jordan chain. Motivated by this structure, we construct a logical-qubit basis directly from the Liouvillian eigenmodes, thereby incorporating both measurement-induced dissipation and error processes into the encoded subspace. By analyzing the Jordan chain at the EP, we identify dynamical features that enhance logical-state stability over short and intermediate times. We then optimize the logical basis to reproduce these EP-induced properties for arbitrary error rates, effectively extending the favorable dynamical behavior beyond the singular point.

Keywords: Exceptional Points; Continuous Measurement; Qubit Encoding