Author: Lisa

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Solving quantum impurity problems with matrix-product states in the temporal domain We introduce an efficient method to simulate dynamics of an interacting quantum impurity coupled to non-interacting fermionic reservoirs, based on a matrix-product state (MPS) representation of the reservoirs’ Feynman-Vernon influence functionals (IF). The efficiency of such representation rests on the moderate entanglement of the IF viewed as a “temporal state”, dubbed temporal entanglement (TE). By analytically studying TE for a general class of reservoir’s initial states, we establish that for initial states with finite-range correlations TE obeys an area law, whereas Fermi-sea-type initial states yield logarithmic scaling of TE with time, closely related to the scaling of real-space entanglement in (1+1)-dimensional conformal field theory. Hence, we describe an explicit algorithm for converting the IF temporal state to an optimal MPS form, which can be subsequently contracted with arbitrary impurities with modest effort. We apply our method to quantum quenches and transport in a single- and multi-level impurity Anderson model, including highly non-equilibrium setups, and find favorable performance compared to state-of-the-art methods. The polynomial scaling of computational resources required for an accurate computation of dynamics indicates that a broad class of out-of-equilibrium quantum impurity problems are efficiently solvable.

From the 3rd to the 8th of March, Alice and Daniel attended the American Physical Society’s March Meeting 2024 in Minneapolis, a scientific research conference convening 13,000 physicists and students from around the world to connect and collaborate across academia, industry, and major labs. Check out thier slides [1, 2] for the March meeting on quantum optimal control and Rydberg atoms.

Francesco attended the second workshop of the series on quantum many-body systems out of equilibrium, organised by Prof. Rosario Fazio at the Institut Henri Poincaré in Paris. Francesco also presented his work at Dr Marco Schirò’s group at College the France, and collaborated with Dr Gian Marcello Andolina and Junior Prof. Filippo Vicentini.

Avvisi pubblici per la presentazione di proposte progettuali di attività di Ricerca finanziate dall’Unione europea nell’ambito di NextGenerationEU, con fondi MUR PNRR Missione 4 Componente 2, Investimento 1.3, 1.4 e 1.5, rivolti a soggetti esterni ai Centri Nazionali, ai Partenariati Estesi e agli Ecosistemi dell’Innovazione, quali: le Micro, Piccole e Medie imprese (MPMI), esterne al CN e che concorrono in modalità singola, aventi i parametri dimensionali di cui all’allegato I del REG (CE) n. 800/2008 della Commissione del 6 agosto 2008 (Regolamento generale di esenzione per categoria) in GUUE L 214 del 9.8.2008 le Grandi Imprese (GI), esterne al CN le Università italiane Statali, esterne al CN le Università italiane non Statali legalmente riconosciute ed accreditate MUR, esterne al CN gli Organismi di Ricerca (OdR) ai sensi del regolamento (UE) 651/2014, punto 83, esterni al CN La deadline per la partecipazione è il 12/02/2024 mentre tutti i dettagli sono disponibili nel bando.  

Phila, who finished her PhD in our group in 2022, has been honoured with the “Ernst-Ising-Dissertation-Prize” for outstanding physics dissertations from the University of Cologne. The annual award is kindly sponsored by the Wilhelm and Else Heraeus Foundation. Phila’s thesis, titled “Quantum Optimal Control of Spin Systems and Trapped Atoms,” has been selected as one of two recipients for the year 2022. Her dissertation is concerned with the improvement of quantum optimal control methods and their application to a range of systems. Thus it shows how these control strategies interconnect and boost the rise of quantum technologies across different platforms. Phila conducted her PhD between the Universities of Cologne and Padua in the groups of Prof Tommaso Calarco and Prof Simone Montangero. The official award ceremony will take place in Cologne in spring 2024.