Środowiskowe Seminarium z Informacji i Technologii Kwantowych

In this talk I will give an overview of a few recent projects related to various topics in quantum information.Driven quantum systems subject to non-Markovian noise are typically difficult to model even if the noise is classical. In the first part of my talk, I will present a systematic method based on a generalized cumulant expansion for deriving a time-local master equation for such systems [1]. I will outline some key features of such a master equation, and show that it can lead to dynamics that is much more accurate than a more standard method that is often used for modeling the effects of correlated noise.In the second part, I will explore how dissipative dynamics of ensembles of two-level systems can be used to enhance Ramsey-based quantum metrology approaches that are limited by detection noise [2]. In particular I will explore how a collective spin decay, an effect that is usually seen as a nuisance because it limits spin-squeezing protocols, can allow a system with extremely imperfect detection to approach the standard-quantum-limit (SQL) within a factor of about (approximately) 2.Finally, I will briefly discuss scqubits: an open-source Python package for simulating and analyzing superconducting circuits [3]. I will outline its core functionality, features, as well as limitations.
[1] PG, A Seif, J Koch, AA Clerk, Quantum 7, 972 (2023)[2] M Koppenhöfer, PG, H-K Lau, AA Clerk, PRX Quantum 3 (3), 030330 (2022)[3] PG, J Koch, Quantum 5, 583 (2021)