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Nonlinear Probes of quantum localized systems

English title Nonlinear Probes of quantum localized systems
Applicant Müller Markus
Number 166271
Funding scheme Project funding (Div. I-III)
Research institution Condensed Matter Theory Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Condensed Matter Physics
Start/End 01.03.2017 - 30.04.2021
Approved amount 532'989.00
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Keywords (6)

many-body localization; hole burning; LiHoF4; quantum entanglement; quantum computing; quantum annealing

Lay Summary (German)

Lead
Dynamische Lokalisierung ist ein subtiler Mechanismus in Quantensystemen, der es komplexen, ungeordneten Systemen erlaubt, beliebig lange ausserhalb des thermodynamischen Gleichgewichts zu bleiben, auch wenn das System sehr viele Freiheitsgrade enthält. Dies läuft der Ergodenhypothese entgegen, nach der grosse Systeme immer sehr rasch zum recht formlosen Gleichgewicht tendieren. Lokalisierung ermöglicht es, einen Teil der in einem Zustand enthaltenen Information beizubehalten und weiterzuverarbeiten, ohne deren Quantenkohärenz zu zerstören, was für Anwendungen interessant ist. Bisher gibt es noch wenige experimentelle Resultate, die dieses Phänomen demonstrieren und für interessante Effekte ausnutzen. Diese Lücke schliesst das Projekt am Beispiel von Quantenmagneten.
Lay summary

Lead

Dynamische Lokalisierung ist ein subtiler Mechanismus in Quantensystemen, der es komplexen, ungeordneten Systemen erlaubt, beliebig lange ausserhalb des thermodynamischen Gleichgewichts zu bleiben, auch wenn das System sehr viele Freiheitsgrade enthält. Dies läuft der Ergodenhypothese entgegen, nach der grosse Systeme immer sehr rasch zum recht formlosen Gleichgewicht tendieren.  Lokalisierung ermöglicht es, einen Teil der in einem Zustand enthaltenen Information beizubehalten und weiterzuverarbeiten, ohne deren Quantenkohärenz zu zerstören, was für Anwendungen wichtig ist. Bisher gibt es noch wenige experimentelle Resultate, die dieses Phänomen demonstrieren und für interessante Effekte ausnutzen. Diese Lücke schliesst das Projekt am Beispiel von Quantenmagneten.

Inhalt und Ziele des Forschungsprojekts

Hier soll die Lücke zwischen theoretischen Vorhersagen einerseits und Experimenten andererseits geschlossen werden. Speziell werden lokalisierende Quantenmagneten studiert, wobei Experimente an gut charakterisierten magnetischen Materialien Hand in Hand gehen mit theoretischen Untersuchungen. Insbesondere sollen Signaturen der Lokalisierung, z.B. das spektrale Löcherbrennen, untersucht und mit theoretischen Rechnungen und Modellen verglichen werden. Dies ist uns mit zwei verschiedenen Litium-fluoriden, die magnetische seltene Erden (Holmium oder Terbium) enthalten. Durch unsere theoretische und experimentelle Forschung haben verstanden, wie deren Kern- und Elektronenspins zusammenwirken und unter welchen Bedingungen sie quantenmechanisch gut geschützte Objekte abgeben. Die lange Kohärenz solcher Objekte haben wir dann dazuausgenutzt um dynamische Lokalisierung anderer magnetischer Bestandteile zu charakterisieren.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Das Projekt befasst sich mit Grundlagenforschung im Gebiet der Quantenkohärenz in Festkörpern. Es leistet einen Beitrag zum Verständnis, wie die Quantenphysik von vielen Freiheitsgraden studiert, ausgenutzt und verarbeitet werden kann. Dies ist sowohl für zukünftige quantentechnologische Anwendungen relevant als auch für verschiedene Aspekte im festkörperbasierten Quantencomputing.

Direct link to Lay Summary Last update: 29.03.2021

Responsible applicant and co-applicants

Employees

Publications

Publication
Universal Quantum Computing Using Electronuclear Wavefunctions of Rare-Earth Ions
Grimm Manuel, Beckert Adrian, Aeppli Gabriel, Müller Markus (2021), Universal Quantum Computing Using Electronuclear Wavefunctions of Rare-Earth Ions, in PRX Quantum, 2(1), 010312-010312.
Ultra-high-resolution software-defined photonic terahertz spectroscopy
Hermans Rodolfo I., Seddon James, Shams Haymen, Ponnampalam Lalitha, Seeds Alwyn J., Aeppli Gabriel (2020), Ultra-high-resolution software-defined photonic terahertz spectroscopy, in Optica, 7(10), 1445-1445.
Taking advantage of multiplet structure for lineshape analysis in Fourier space
Beckert Adrian, Sigg Hans, Aeppli Gabriel (2020), Taking advantage of multiplet structure for lineshape analysis in Fourier space, in Optics Express, 28(17), 24937-24937.
Testing of asymptomatic individuals for fast feedback-control of COVID-19 pandemic
Müller Markus, Derlet Peter M, Mudry Christopher, Aeppli Gabriel (2020), Testing of asymptomatic individuals for fast feedback-control of COVID-19 pandemic, in Physical Biology, 17, 065007.

Collaboration

Group / person Country
Types of collaboration
G. Jeschke Switzerland (Europe)
- Publication
- Research Infrastructure
Tom Rosenbaum, CalTech United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
Karl Kraemer, University Bern Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
QSIT Lunch seminar Individual talk Quantum Computing with rare earth ions 03.06.2021 ETH Zürich, Switzerland Grimm Manuel;
Interactive CUNY/BU workshop: Driving, tuning and controlling correlated systems: From switching to quantum computation Talk given at a conference Using nuclear spins and hyperfine coupling to control and manipulate quantum matter 30.04.2021 New York, United States of America Müller Markus;
Group Meeting N. Spaldin ETH Individual talk Quantum computation with rare earth ions 23.01.2020 Zürich, Switzerland Grimm Manuel;
Nonequilibrium Dynamics In Correlated Systems And Quantum Materials Talk given at a conference Many-body localization in a dense interacting quantum system 15.12.2019 Krvavec, Slovenia Aeppli Gabriel;
PSI Condensed Matter Retreat Talk given at a conference Quantum computation with rare earth ions 30.10.2019 Brugg, Switzerland Grimm Manuel;
CMT Seminar Individual talk Coherence and quantum computing with rare earth magnets 22.08.2019 Nordita Stockholm, Sweden Müller Markus;
CMT Seminar Individual talk Hole burning in rare earth magnets 12.07.2019 City University of NY, United States of America Müller Markus;
Breakdown Of Ergodicity In Isolated Quantum Systems Talk given at a conference Localization and coherence of electron-nuclear spin excitations in rare earth magnets 07.06.2019 GGI Florence, Italy Müller Markus;
Condensed Matter Theory Seminar Individual talk Coherent oscillators, spectral hole-burning and emerging q-bits in rare earth magnets 16.05.2019 TU Dresden, Germany Müller Markus;
PSI photon science mini symposium Talk given at a conference LiY1-xHoxF4: a candidate material for solid-state qubits 01.05.2019 PSI Villigen, Switzerland Beckert Adrian;
MaNEP Winter School 2019 Poster LiY1-xHoxF4: a candidate material for solid-state qubits 08.01.2019 Les Diablerets, Switzerland Beckert Adrian;
TTCM 2018 Poster Holeburning in LiHoYF4 08.10.2018 Genf, Switzerland Grimm Manuel;
Workshop on Strong Electron Correlations in Quantum Materials: Inhomogeneities, Frustration, and Topology Talk given at a conference Many-body localization in a dense interacting quantum system 14.08.2018 Sao Paolo, Brazil Aeppli Gabriel;
Conference on Quantum Dynamics of Disordered Interacting Systems Talk given at a conference Coherent oscillators and spectral hole-burning in rare earth magnets 11.06.2018 ICTP Trieste, Italy Grimm Manuel; Müller Markus;
Swiss-Sino Workshop Talk given at a conference Emergence of coherent oscillators in rare earth magnets 07.05.2018 PSI Villigen, Switzerland Müller Markus;
SPIE Photonics Europe, Strasbourg Individual talk LiY(1-x) HoxF4 – a candidate material for the implementation of solid state qubits 01.04.2018 Strasbourg, France Beckert Adrian;
BU/ICAM Workshop on Nonthermal Quantum Matter Talk given at a conference Many-body localization in a dense interacting quantum system 12.03.2018 Boston, United States of America Aeppli Gabriel;
Gordon Research Conf on Ultrafast phenomena in cooperative systems Poster LiY1-xHoxF4: a candidate material for solid-state qubits 01.02.2018 Houston TX, United States of America Beckert Adrian;
PSI condensed matter retreat Talk given at a conference LiY(1-x) HoxF4 – a candidate material for the implementation of solid state qubits 01.11.2017 Brugg, Switzerland Beckert Adrian;


Self-organised

Title Date Place
LiREF Meeting PSI/ETH/EPFL 24.09.2019 Zürich, Switzerland
LiREF Meeting PSI/ETH/EPFL 20.05.2019 PSI Villigen, Switzerland
Li REF Meeting PSI/ETH/EPFL 06.10.2017 Lausanne, Switzerland
LiREF Meeting PSI/ETH/EPFL 22.06.2017 Zurich, Switzerland

Awards

Title Year
Posterpreis der NES Division (PSI) 2018

Associated projects

Number Title Start Funding scheme
133815 Setup for studies of quantum phenomena in condensed matter systems at ultra-low temperatures in magnetic vector fields 01.04.2012 R'EQUIP
170760 High-field THz source for pump-probe experiments at SwissFEL 01.11.2017 R'EQUIP
146870 Quantum Magnetism - Spinons, Skyrmions and Dipoles 01.04.2013 Project funding (Div. I-III)
183304 Microwaves for coherent control of quantum matter and magnonic devices 01.12.2018 R'EQUIP
200558 Off-equilibrium quantum magnetism 01.10.2021 Project funding (Div. I-III)
183330 CristallinaXTREME: X-ray Diffraction under Extreme Conditions 01.11.2019 R'EQUIP

Abstract

Localisation in quantum systems remains both fundamental to science as well as technology. It is an old subject, starting with the work of Anderson, whose name is associated with disorder-induced localisation - and Mott who predicted a localisation transition due to the repulsion between electrons. The combined problem of many-body localisation persists to this day, despite considerable recent theoretical progress. Over the last few years, the problem has acquired practical relevance for systems of quantum devices, most notably the "D-wave" processor which attempts to implement adiabatic quantum computation, whose utility as a matter of principle may be limited by localisation effects. Indeed, such effects may impede the adiabatic adjustment of the system ground state, as well as finite temperature thermalisation. However, from an opposite point of view, this is a highly desired effect: Interacting but nevertheless localised systems constitute promising platforms for the quantum information processing of coherent, spatially localised degrees of freedom in thermodynamically large systems.These developments notwithstanding, there are few sharp experimental results in the field, and theory has not focused on devising detailed experimental tests. The present proposal joins experiment and theory to focus on a particular probe of localised states, namely the non-linear response function and spectral hole-burning in quantum magnets. Those are solid state materials which combine several features that favour localisation. The compounds under study will be the rare earth (RE) lithium fluorides, which exhibit a variety of ordered and disordered magnetic states as a function of random occupancy of the RE site by magnetic and non-magnetic ions. They also undergo quantum phase transitions as a function of transverse field imposed in the laboratory. The combination of a well-specified Hamiltonian, tunable disorder and quantum fluctuations made these insulators the original testbed for "quantum annealing". They exhibit saturation in their non-linear response and the phenomenon of spectral hole-burning, which suggest spatial localisation of excitations despite the interacting environment.Recent measurements further indicate a strong dependence of the non-linear response on transverse field, as well as on the coupling to the external thermal bath. The existing data are understood only at a qualitative level, especially because there are neither theory nor data as to the underlying microscopic spin correlations at the origin of the collective degrees of freedom that remain quantum coherent, despite their embedding in the solid. In this project, we will develop the phenomenology as well as microscopic theory. We will perform the neutron and X-ray scattering measurements that yield space- and time-dependent spin correlation functions, also in the presence of the AC drive fields responsible for hole-burning. The combination of these efforts is expected to provide an understanding of hole-burning and the emergence of quantum coherence in quantum magnets and advance the understanding of many-body localisation in general.Our project entails the first targeted experimental and theoretical study of many-body localisation in a magnetic material, thereby lifting the field of many-body localisation to a new level and paving the way towards firm conclusions about the implications of many-body localisation for quantum information.
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