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About myself

I am a theoretical physicist working at the intersection between nanophysics and quantum optics.

Since August 2016, I am director at the Max Planck Institute for the Science of Light in Erlangen. I also hold a part-time position at the university.

CV Florian Marquardt

Florian Kai Marquardt (Dr. phil.)


Born 16.7.1974 in Berlin (Berlin-Charlottenburg), Federal Republic of Germany; German citizenship

Theoretical Physicist, with research mostly at the intersection between nanophysics and quantum optics

Research topics: optomechanics, quantum optics, decoherence, electronic transport in nanostructures, superconducting circuit cavity quantum electrodynamics, nonequilibrium quantum many-body physics, classical nonlinear dynamics


  • 2016-now Scientific Director at the Max Planck Institute for the Science of Light, Erlangen, Germany. Part-time professor at the university in Erlangen.
  • 2010-2016 Full professor (chair) at Universität Erlangen-Nürnberg at Erlangen, Germany
  • 2005-2010 Junior research group leader (junior professor, Emmy-Noether program) at Ludwig-Maximilians Universität München (LMU), Germany
  • 2003-2005 Postdoctoral fellow at Yale University, USA (group of Steve Girvin)
  • 2002-2003 Postdoctoral fellow in the Swiss National Center for Competence in Research in Nanoscale Science (NCCR), Basel
  • 1999-2002 PhD student at the University of Basel, Switzerland (group of Christoph Bruder)


  • 1999-2002 PhD student at the University of Basel, Switzerland (group of Christoph Bruder); Thesis on "Models of dephasing at low temperatures"; "summa cum laude"
  • 1992-1993, 1994-1998 Studies of physics (Diplom), Universität Bayreuth, Germany; Diploma thesis on vortex motion in superconductors (with Prof. Dierk Rainer); Diploma "with distinction"
  • 1992 Abitur (final high school exam) at Theodor-Heuss Gymnasium Nördlingen, Germany; final grade 1.0

Awards, fellowships and significant grants

  • 2007: Emmy-Noether group leader fellowship of the German Science Foundation (DFG), grant period: 2007-2012
  • 2009: Walter Schottky prize 2009 of the German Physical Society (DPG), "for groundbreaking work on the theory of optomechanical systems"
  • 2011: ERC Starting Grant of the European Research Council, grant period: 2011-2016


Main Scientific Achievements

My main contributions to science are at the intersection between nanophysics and quantum optics, and especially in the new field of cavity optomechanics. Cavity optomechanics deals with the interaction between light and mechanical motion. I started working on the theory of optomechanics in 2004, during my postdoc stay at Yale, jointly with Steve Girvin and Jack Harris. At the time, optomechanics was not a visible research area, despite pioneering work dating back much earlier (Braginsky in the 70s, the Walther group at the MPQ in the 80s, the LKB group around Heidmann in the 90s, and some theory work by the Knight group and the Tombesi group in the 90s). In 2004, we worked out the classical nonlinear dynamics of cavity-optomechanical systems, predicting the nonlinear attractor diagram (arXiv Feb 05, PRL 06). This has now become the cornerstone for any work on nonlinear dynamics in optomechanics. The timing was fortunate: While we completed our analysis, the Karrai group published the first experiment on intrinsic back-action cooling of a cavity-optomechanical system using photothermal forces, and shortly after completion of our work, the Vahala group announced their experimental observations of optomechanical dynamics in microtoroids.

Starting in 2006, the field of cavity optomechanics rapidly attracted increased attention, with a number of new systems becoming available. One of the primary goals in this early stage was laser-cooling of mechanical motion. At the beginning of 2007, we published the complete quantum theory of optomechanical cooling, predicting the fundamental quantum limits set by the laser shot noise (arXiv Jan 07, PRL 07). This became the theoretical foundation for all subsequent experiments on optomechanical laser-cooling down to the ground state (finally achieved in 2011). In the same work, we also predicted what afterwards became known as the strong-coupling regime of optomechanics, where the optical and mechanical mode hybridize to form new 'photon-phonon polaritons'. That is the regime now being used for state swap between mechanical and optical quantum states.

Starting in 2009, I became interested in the many-body dynamics of optomechanical systems, inspired by the newly available experimental platform of photonic crystals. Our group was the first to propose "optomechanical arrays" in the form of an array of coupled localized optical and mechanical modes (arXiv Jul 10, PRL 11). Several years later, such arrays are now becoming available experimentally, e.g. in the form of coupled disk resonators (Lipson group Cornell/Columbia) and photonic crystal coupled cavity arrays (Painter group Caltech). In the classical regime, their dynamics is described by nonlinear stochastic field theories, which are of high intrinsic theoretical interest, and they display rich collective dynamics (such as the synchronization predicted in our 2011 work, or pattern formation). As we showed later, they will also serve as a platform for quantum many-body physics and as 'metamaterials' that allow the optically tunable transport of photons and phonons. In this way, optomechanical arrays could become for photons and phonons what 'optical lattices' are for cold atoms.

One of the most exciting developments regarding our understanding of transport and bandstructures is the recent realization that topological properties of matter waves can be crucially important. In this context, we have been able to provide the first proposal for topologically protected transport of sound waves in the solid state (arXiv Sep 14, PRX 15). Engineering such transport is a nontrivial task, since it requires to impart non-reciprocal phases onto the motion of these sound waves. We have shown how to exploit the optomechanical interaction for this purpose, which has the added benefit of generating a system that can be optically tuned, excited, and read out. This is in contrast to later proposals and experiments (from 2015 onwards) that rely on a fixed geometry. The field of phonon topological transport is currently still in its infancy (in contrast to the cases of electrons, photons, and cold atoms), and the optomechanical approach will offer significant flexibility in this area.

In addition to optomechanics, my work has covered areas such as decoherence, superconducting qubits, and general many-body physics. For example, in a very early work on superconducting qubits, we introduced the Jaynes-Cummings model from atomic physics into the area of superconducting circuits (PRB 01), and this served as one of the precursors for the subsequent circuit cavity QED developments at Yale.

You may read more on our Research page.

Participation in network grants (selected)

  • "Sonderforschungsbereich (SFB) 631" of the German Science Foundation (DFG), on solid-state based quantum information processing (Principal Investigator), 2007-2010
  • SFB/Transregio 12, on "Symmetries and Universality in Mesoscopic Physics" (Investigator), 2007-2011
  • Nanosystems Initiative Munich (NIM), cluster of excellence within the excellence initiative of the DFG (Junior Investigator), 2006-2010
  • DARPA Grant "ORCHID" on optomechanical systems, DARPA agency, USA (Principal Investigator), 2010-2015
  • European Marie-Curie Initial Training Network (ITN) on cavity optomechanics (cQOM), PI, 2012-2016

Invited talks

(Co-)Organization of Conferences (selected)

  • 2008 International Workshop "Nanomechanical systems approaching the quantum regime" at the Arnold Sommerfeld Center for Theoretical Physics, Munich (with E. Weig, J. v. Delft, W. Zwerger, M. Khiselev)
  • 2009 438. Heraeus Seminar "Quantum Optics of Nano- and Micromechanical Systems", Bad Honnef (with M. Aspelmeyer and T. Kippenberg)
  • 2013 International Centre for Theoretical Physics Trieste, Workshop on "Frontiers of Nanomechanics" (with M. Blencowe, J. v. Delft, I. Favero, K. Lehnert, and E. Weig, and M. Khiselev)
  • 2014 Gordon Research Conference "Mechanical Systems in the Quantum Regime", Ventura Beach, California (with A. Clerk)
  • 2015 Les Houches Summer School "Optomechanics" (with P.-F. Cohadon and J. Harris)


  • Special lectures on: "Mesoscopic physics and nanophysics" (summer 2005 and 2006), "Open quantum systems" (winter 2005/06), "Theoretical solid state physics" (winter 2006/07), "Quantum-coherent nanostructures" (summer 2007), "Nanophysics and quantum optics" (summer 2010), "Recent progress in cavity optomechanics" (winter 2012/13), "Foundations of Quantum Mechanics" (summer 2013)
  • Regular undergraduate course lectures on: Thermodynamics and Statistical Physics (winter 2010/11, winter 2014/15), Theoretical physics for material physicists (statistical physics; summer 2011, summer 2012), Advanced Quantum Mechanics (winter 2011/12, winter 2013/14), "Quanta and fields" for material physicists (winter 2012/13)
  • Lecturing at various schools: "Summer School on Quantum Hall Systems and Quantum Dots" (September 2006) in Turkey, summer school "Quantum Noise and Quantum Optics in the Solid State" at Bad Honnef (August 2007), Windsor Summer School on Condensed Matter Physics (Windsor, UK, August 2010), Les Houches workshop on "Quantum Machines" (July 2011), Summer school attached to the QIPC 2011 conference at Diavolezza, Switzerland (September 2011), Tutorial lecture on graphene at the Newton Institute Workshop on Relativistic Operators in Cambridge (July/August 2012), ITN cQOM school and workshop at Erlangen and Munich (October 2013), Workshop at Fai della Paganella (Januar 2014)
  • Co-organizer of workshops and schools: Arnold Sommerfeld summer school (Munich) in October 2007, "Nanomechanical systems approaching the quantum regime" (Munich, September 2008), workshop "Interactions in Hybrid Nanosystems" of the Nanosystems Initiative Munich at Chiemsee (May 2008), Bad Honnef workshop on optomechanics (summer 2009), "Frontiers of Nanomechanics" (2013 International Centre for Theoretical Physics Trieste), "Mechanical Systems in the Quantum Regime" (2014 Gordon Research Conference, Ventura Beach, California), Les Houches Summer School "Optomechanics" (2015)

Video recordings of lectures:

My aims in research and teaching

I have learned one good rule from successful theorists, which is: keep things as simple as possible. The idea is not to solve the most complicated problem with the most sophisticated methods. Rather I always want to capture the essential features in a simplified model, and to work out its crucial aspects in the simplest way possible. At least, that is the goal.

In teaching, I try to emphasize the physics. I always try to prevent good students from getting carried away with the mathematics (even though mastery of the mathematical machinery is important, of course).

Public calendar

I have set up a public calendar, so you can see in advance when and where I will be traveling. This is useful for arranging meetings and scheduling talks etc. It should be up-to-date, as it is directly published from my iCal calendar on my Mac.