# Helmut Ritsch
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{{Short description|Austrian physicist}}
{{Infobox scientist
| name = Helmut Ritsch
| image = Helmut Ritsch
| birth_date = {{Birth date and age|1962|03|12|df=y}}
| birth_place = [Innsbruck](/source/Innsbruck), [Austria](/source/Austria)
| fields = {{ubl|[Physics](/source/Physics)|[Quantum mechanics](/source/Quantum_mechanics)|[Quantum optics](/source/Quantum_optics)}}
| workplaces = {{ubl|[University of Innsbruck](/source/University_of_Innsbruck)|[University of Konstanz](/source/University_of_Konstanz)|[JILA, University of Colorado (Boulder)](/source/JILA)|[University of Milan](/source/University_of_Milan)}}
| alma_mater = [University of Innsbruck](/source/University_of_Innsbruck)
| thesis_title = Atomic Dynamics in Classical Stochastic and Quantum Light Fields
| doctoral_advisor = [Peter Zoller](/source/Peter_Zoller)
| known_for = {{ubl|[Cavity QED](/source/Cavity_quantum_electrodynamics)|[Monte Carlo wave function (MCWF) method](/source/Quantum_jump_method)}}
| awards = {{ubl|[Ludwig Boltzmann Prize](/source/Ludwig_Boltzmann_Prize) (1993)|[Erwin Schrödinger Prize](/source/Erwin_Schr%C3%B6dinger_Prize) (2019)}}
| spouse = [Monika Ritsch-Marte](/source/Monika_Ritsch-Marte)
}}
'''Helmut Ritsch''' ({{IPA|de|ˈHɛlmuːt ʀɪtʃ|lang}}; born 12 March 1962 in [Innsbruck](/source/Innsbruck)) is an [Austria](/source/Austria)n [quantum physicist](/source/Quantum_mechanics) and a professor of [theoretical physics](/source/theoretical_physics) at the [University of Innsbruck](/source/University_of_Innsbruck).[{{cite web|title=Univ.-Prof. Mag. Dr. Helmut Ritsch, Institut für Theoretische Physik| publisher=[University of Innsbruck](/source/University_of_Innsbruck)|url=https://www.uibk.ac.at/th-physik/staff/ritsch|access-date=2023-01-15|year=|language=en|pages=|quote=}}][{{cite web|title=Research Group Theoretische Physik, Univ. Innsbruck (Univ. Prof. Helmut Ritsch)|url=https://www.oepg.at/index.php?page=research&use_js=0&step=2&ID1=61&lang=en|publisher=[Austrian Physical Society](/source/Austrian_Physical_Society)}}]
Helmut Ritsch's research concerns the fundamental aspects and applications of [quantum optics](/source/quantum_optics) and [cavity quantum electrodynamics](/source/cavity_quantum_electrodynamics).[{{citation |title=Erwin Schrödinger-Preis 2019: Helmut Ritsch |url=https://stipendien.oeaw.ac.at/en/preise/naturwissenschaften/erwin-schroedinger-preis/preistraeger-innen/helmut-ritsch|publisher=[Austrian Academy of Sciences](/source/Austrian_Academy_of_Sciences)|language=de}}] Together with his theory group, he focuses on [cavity](/source/Optical_cavity) cooling, self-organization, [quantum thermodynamics](/source/quantum_thermodynamics), light forces, [superradiant lasing](/source/Superradiant_laser) and [quantum metrology](/source/quantum_metrology).[{{citation |title=Ritsch Helmut - Google Scholar |url=https://scholar.google.at/citations?user=0ePFxuEAAAAJ&hl=en}}] His significant contributions in those fields have been honoured with prestigious awards and prizes, as the [Ludwig Boltzmann Prize](/source/Ludwig_Boltzmann_Prize) (1993) of the [Austrian Physical Society](/source/Austrian_Physical_Society)[{{citation|title=Awardees of the ÖPG|url=https://www.oepg.at/index.php?page=awards&subpage=winner&lang=en|publisher=[Austrian Physical Society](/source/Austrian_Physical_Society)|access-date=2023-01-15|archive-date=2023-01-15|archive-url=https://web.archive.org/web/20230115170257/https://www.oepg.at/index.php?page=awards&subpage=winner&lang=en}}]
and the [Erwin Schrödinger Prize](/source/Erwin_Schr%C3%B6dinger_Prize) (2019) of the [Austrian Academy of Sciences](/source/Austrian_Academy_of_Sciences).[{{cite web|title= Höchste Wissenschaftspreise der ÖAW verliehen|publisher=[Austrian Academy of Sciences](/source/Austrian_Academy_of_Sciences) |url=https://www.oeaw.ac.at/detail/news/hoechste-wissenschaftspreise-der-oeaw-verliehen/|format=|access-date=2022-12-19|last=|date=|year=|language=de|pages=|quote=}}]
== Life and career==
Ritsch grew up in [Stubaital](/source/Stubaital) in the neighbourhood of [Innsbruck](/source/Innsbruck). He graduated in 1980 from [Akademischen Gymnasium in Innsbruck](/source/Akademisches_Gymnasium_Innsbruck) and studied physics at the [University of Innsbruck](/source/University_of_Innsbruck), where he finished his diploma study in 1985 with a thesis about synchrotron radiation. He began his doctoral studies under [Peter Zoller](/source/Peter_Zoller), which he finished in 1989 with the dissertation "Atomic Dynamics in Classical Stochastic and Quantum Light Fields". Afterwards he worked as a postdoc in Innsbruck, Konstanz, Milan, Boulder and Munich.[{{cite journal |last1=Domoskos |first1=Peter |last2=Ritsch |first2=Helmut |year=2002 |title=Collective Cooling and Self-Organization of Atoms in a Cavity |journal=Physical Review Letters |publisher=APS |volume=89 |issue=25 |article-number=253003 |doi=10.1103/PhysRevLett.89.253003|pmid=12484881 |bibcode=2002PhRvL..89y3003D }}][{{cite journal |last1=Black |first1=Adam |last2=Chan |first2=Hilton |last3=Vuletic |first3=Vladan |year=2003 |title=Observation of Collective Friction Forces due to Spatial Self-Organization of Atoms: From Rayleigh to Bragg Scattering |journal=Physical Review Letters |publisher=APS |volume=91 |issue=20 |article-number=203001 |doi=10.1103/PhysRevLett.91.203001|pmid=14683358 |bibcode=2003PhRvL..91t3001B }}] as a manifestation of the Dicke superradiant [phase transition](/source/phase_transition). This phenomenon has been observed in many experiments, ranging from Bose-Einstein condensates[{{citation | title= Dicke quantum phase transition with a superfluid gas in an optical cavity | date=2010| doi=10.1038/nature09009| url=https://www.nature.com/articles/nature09009| last1=Baumann| first1=Kristian| last2=Guerlin| first2=Christine| last3=Brennecke| first3=Ferdinand| last4=Esslinger| first4=Tilman| journal=Nature| volume=464| issue=7293| pages=1301–1306| pmid=20428162| arxiv=0912.3261| bibcode=2010Natur.464.1301B}}] to non-interacting[{{citation | title = Observation of a superradiant quantum phase transition in an intracavity degenerate Fermi gas| year = 2021| doi = 10.1126/science.abd4385| last1 = Zhang| first1 = Xiaotian| last2 = Chen| first2 = Yu| last3 = Wu| first3 = Zemao| last4 = Wang| first4 = Juan| last5 = Fan| first5 = Jijie| last6 = Deng| first6 = Shujin| last7 = Wu| first7 = Haibin| journal = Science| volume = 373| issue = 6561| pages = 1359–1362| pmid = 34446446| s2cid = 237325206| doi-access = free| bibcode = 2021Sci...373.1359Z}}] and strongly interacting[{{citation | title = Density-wave ordering in a unitary Fermi gas with photon-mediated interactions| arxiv = 2212.04402| last1 = Helson| first1 = Victor| last2 = Zwettler| first2 = Timo| last3 = Mivehvar| first3 = Farokh| last4 = Colella| first4 = Elvia| last5 = Roux| first5 = Kevin| last6 = Konishi| first6 = Hideki| last7 = Ritsch| first7 = Helmut| last8 = Brantut| first8 = Jean-Philippe| journal = Nature| year = 2023| volume = 618| issue = 7966| pages = 716–720| doi = 10.1038/s41586-023-06018-3| pmid = 37225993| pmc = 10284702| bibcode = 2023Natur.618..716H}}] Fermi gases. The atomic self-organization in cavities is currently an active field of research, with the prospect to address some of the most challenging, open questions in nonequilibrium many-body physics in a controlled way.[{{cite journal |last1=Mivehvar |first1=Farokh |last2=Piazza |first2=Francesco |last3=Donner |first3=Tobias |last4=Ritsch |first4=Helmut |title=Cavity QED with quantum gases: new paradigms in many-body physics |journal=Advances in Physics |date=2 January 2021 |volume=70 |issue=1 |pages=1–153 |doi=10.1080/00018732.2021.1969727 |s2cid=231855430 |url=https://www.tandfonline.com/doi/abs/10.1080/00018732.2021.1969727 |issn=0001-8732|arxiv=2102.04473 |bibcode=2021AdPhy..70....1M }}]
=== Monte Carlo wave function (MCWF) method ===
{{Main|Quantum jump method}}
Monte Carlo wave function method, also known as quantum jump method, is a computational tool used in dissipative systems to approximate the density matrix of a quantum system. The method was developed in 1992 independently by Dum, Zoller and Ritsch and Dalibard, Castin and Mølmer.
=== QuantumOptics.jl ===
QuantumOptics.jl[{{Cite web |title=A Julia Framework for Open Quantum Dynamics |url=https://qojulia.org}}] is a numerical framework written in the [Julia](/source/Julia_(programming_language)) that facilitates simulations of various kinds of [open quantum system](/source/open_quantum_system)s. It is inspired by the Quantum Optics Toolbox for MATLAB and the Python framework [QuTiP](/source/QuTiP). QuantumOptics.jl is being developed in Helmut Ritsch's CQED group at the Institute for Theoretical Physics of the [University of Innsbruck](/source/University_of_Innsbruck) since 2017, with the 1.0 version being released in July 2021. QuantumOptics.jl remains [open-source](/source/Open-source_software) and is hosted on [GitHub](/source/GitHub). There are several Add-Ons related to and/or dependent on QuantumOptics.jl.[{{Cite web |title=QuantumOptics.jl Add-Ons |url=https://qojulia.org/addons}}] For example, QuantumCumulants.jl[{{Cite web |title=QuantumCumulants.jl |url=https://github.com/qojulia/QuantumCumulants.jl |publisher=[GitHub](/source/GitHub)}}] is a package for the symbolic derivation of mean-field equations for quantum mechanical operators in Julia.
=== Dipole-Dipole interactions ===
A significant part of his research also involves the investigation of collective effects of atoms with light-induced interactions, including the emergence of [superadiance](/source/Superradiance) and subradiance in long-range interacting quantum emitters with dipole-dipole interactions.
== Honours and awards ==
* 2019 [Erwin Schrödinger Prize](/source/Erwin_Schr%C3%B6dinger_Prize) of the [Austrian Academy of Sciences](/source/Austrian_Academy_of_Sciences) for his outstanding research achievements in the field of [quantum optics](/source/quantum_optics), in particular for his fundamental contributions to the theoretical understanding of light–matter interaction and [cavity quantum electrodynamics (CQED)](/source/Cavity_quantum_electrodynamics).[{{citation |title=Visiting Fellows
|url=https://jila.colorado.edu/workcollaborate/visiting-fellows-list |publisher=[Joint Institute for Laboratory Astrophysics (JILA)](/source/JILA)}}]
* 2008 Scottish Universities Physics Alliance (SUPA) Distinguished Visitor Award, Glasgow.
* 2004 Dr. Otto Seibert Wissenschafts-Förderungs-Preis.
* 1993 [Ludwig Boltzmann Prize](/source/Ludwig_Boltzmann_Prize) of the [Austrian Physical Society](/source/Austrian_Physical_Society) (jointly with [M. Ritsch-Marte](/source/Monika_Ritsch-Marte)).