Physikalisches Institut (PHI)

Research Group Pop

Dr. Ioan Pop Dr. Ioan Pop


Physikalisches Institut
Wolfgang-Gaede-Str. 1
D-76131 Karlsruhe, Germany

and Institute for Quantum Materials and Technologies (IQMT)

mail ioan.pop∂


PhD: 2011 NEEL Institute, CNRS and University of Grenoble, France
Master degree: 2007 Physics, University of Grenoble, France
Diploma degree: 2006 Physics, Babeș-Bolyai University, Cluj-Napoca, Romania


2011-2015 Postdoctoral researcher, Yale University, USA
2007-2011 NEEL Institute, CNRS, Grenoble, France
2007-2010 Teaching assistant, University of Grenoble, France

We have received the generous support of the Alexander von Humboldt foundation through a Sofja Kovalevskaja Award. 

Fields of research

Our research focuses on superconducting quantum circuits.

Josephson junctions have been proven to be reliable building blocks for superconducting quantum memories, high-speed processing units, amplifiers and detectors, operating in the microwave domain. In these types of electrical circuits, which can be manufactured using standard lithography, currents and voltages can exhibit quantum mechanical properties and can be controlled using microwave pulses. This makes them appealing for the study of fundamental quantum phenomena and the implementation of quantum information processing.

We are currently interested in the design and implementation of quantum circuits protected against decoherence.

PostDocs, PhD and Master students wanted.


Prof. Alexey Ustinov, KIT

Prof. Wolfgang Wernsdorfer, KIT

Selected Publications

  1. Granular aluminum: A superconducting material for high impedance quantum circuits
    L. Grunhaupt, M. Spiecker, D. Gusenkova, N. Maleeva, S. T. Skacel, I. Takmakov, F. Valenti, P. Winkel, H. Rotzinger, A. V. Ustinov, and I. M. Pop
    Nature Materials 18, 816 (2019), doi:10.1038/s41563-019-0350-3
    Featured in:
    by Emily Toomey
    News and Views
    by Joel Jan Wang and William D. Oliver (MIT, USA)

  2. Circuit Quantum Electrodynamics of Granular Aluminum Resonators
    N. Maleeva, L. Grünhaupt, T. Klein, F. Levy-Bertrand, O. Dupré, M. Calvo, F. Valenti, P. Winkel, F. Friedrich, W. Wernsdorfer, A. V. Ustinov, H. Rotzinger, A. Monfardini, M. V. Fistul, and I. M. Pop
    Nature Comm. 9, 3889 (2018), doi:10.1038/s41467-018-06386-9, pdf download (ca. 1.1 MB)

  3. Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum
    L. Grünhaupt, N. Maleeva, S. T. Skacel, G. Catelani, M. Calvo, F. Levy-Bertrand, A. V. Ustinov, H. Rotzinger, A. Monfardini, and I. M. Pop
    Phys. Rev. Lett. 121, 117001 (2018), doi:10.1103/PhysRevLett.121.117001, pdf download (ca. 1 MB)

  4. Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles
    I. M. Pop, K. Geerlings, G. Catelani, R. J. Schoelkopf, L. Glazman and M. H. Devoret
    Nature, 508, 369 (2014), doi:10.1038/nature13017, pdf download (ca. 3.6 MB)

  5. Measurement of the effect of quantum phase-slips in a Josephson junction chain
    I. M. Pop, I. Protopopov, F. Lecocq, Z. Peng, B. Pannetier, O. Buisson and W. Guichard
    Nature Physics, 6, 589-592 (2010), pdf download (ca. 420 kB)

Publications Group Pop

Superconducting granular aluminum resonators resilient to magnetic fields up to 1 Tesla.
Borisov, K.; Rieger, D.; Winkel, P.; Henriques, F.; Valenti, F.; Ionita, A.; Wessbecher, M.; Spiecker, M.; Gusenkova, D.; Pop, I. M.; Wernsdorfer, W.
2020. Applied physics letters, 117 (12), Art.-Nr.: 120502. doi:10.1063/5.0018012
Quantum Versus Classical Switching Dynamics of Driven Dissipative Kerr Resonators.
Andersen, C. K.; Kamal, A.; Masluk, N. A.; Pop, I. M.; Blais, A.; Devoret, M. H.
2020. Physical review applied, 13 (4), Art. Nr.: 044017. doi:10.1103/PhysRevApplied.13.044017
Microscopic charging and in-gap states in superconducting granular aluminum.
Yang, F.; Gozlinski, T.; Storbeck, T.; Grünhaupt, L.; Pop, I. M.; Wulfhekel, W.
2020. Physical review / B, 102 (10), Art.-Nr. 104502. doi:10.1103/PhysRevB.102.104502
Implementation of a Transmon Qubit Using Superconducting Granular Aluminum.
Winkel, P.; Borisov, K.; Grünhaupt, L.; Rieger, D.; Spiecker, M.; Valenti, F.; Ustinov, A. V.; Wernsdorfer, W.; Pop, I. M.
2020. Physical review / X, 10 (3), Art.Nr. 031032. doi:10.1103/PhysRevX.10.031032VolltextVolltext der Publikation als PDF-Dokument
Nondegenerate Parametric Amplifiers Based on Dispersion-Engineered Josephson-Junction Arrays.
Winkel, P.; Takmakov, I.; Rieger, D.; Planat, L.; Hasch-Guichard, W.; Grünhaupt, L.; Maleeva, N.; Foroughi, F.; Henriques, F.; Borisov, K.; Ferrero, J.; Ustinov, A. V.; Wernsdorfer, W.; Roch, N.; Pop, I. M.
2020. Physical review applied, 13 (2), Art. Nr.: 024015. doi:10.1103/PhysRevApplied.13.024015
Onset of phase diffusion in high kinetic inductance granular aluminum micro-SQUIDs.
Friedrich, F.; Winkel, P.; Borisov, K.; Seeger, H.; Sürgers, C.; Pop, I. M.; Wernsdorfer, W.
2019. Superconductor science and technology, 32 (12), 125008. doi:10.1088/1361-6668/ab4918VolltextVolltext der Publikation als PDF-Dokument
Granular aluminium as a superconducting material for high-impedance quantum circuits.
Grünhaupt, L.; Spiecker, M.; Gusenkova, D.; Maleeva, N.; Skacel, S. T.; Takmakov, I.; Valenti, F.; Winkel, P.; Rotzinger, H.; Wernsdorfer, W.; Ustinov, A. V.; Pop, I. M.
2019. Nature materials, 18 (8), 816–819. doi:10.1038/s41563-019-0350-3
DEMETRA: Suppression of the Relaxation Induced by Radioactivity in Superconducting Qubits.
Cardani, L.; Casali, N.; Catelani, G.; Charpentier, T.; Clemenza, M.; Colantoni, I.; Cruciani, A.; Gironi, L.; Gruenhaupt, L.; Gusenkova, D.; Henriques, F.; Lagoin, M.; Martinez, M.; Pirro, S.; Pop, I. M.; Rusconi, C.; Ustinov, A.; Valenti, F.; Vignati, M.; Wernsdorfer, W.
2019. Journal of low temperature physics. doi:10.1007/s10909-019-02265-9
Phonon traps reduce the quasiparticle density in superconducting circuits.
Henriques, F.; Valenti, F.; Charpentier, T.; Lagoin, M.; Gouriou, C.; Martínez, M.; Cardani, L.; Vignati, M.; Grünhaupt, L.; Gusenkova, D.; Ferrero, J.; Skacel, S. T.; Wernsdorfer, W.; Ustinov, A. V.; Catelani, G.; Sander, O.; Pop, I. M.
2019. Applied physics letters, 115 (21), Art.-Nr.: 212601. doi:10.1063/1.5124967
Electrodynamics of granular aluminum from superconductor to insulator: Observation of collective superconducting modes.
Levy-Bertrand, F.; Klein, T.; Grenet, T.; Dupré, O.; Benoît, A.; Bideaud, A.; Bourrion, O.; Calvo, M.; Catalano, A.; Gomez, A.; Goupy, J.; Grünhaupt, L.; Luepke, U. v.; Maleeva, N.; Valenti, F.; Pop, I. M.; Monfardini, A.
2019. Physical review / B, 99 (9), Art. Nr.: 094506. doi:10.1103/PhysRevB.99.094506
Interplay between Kinetic Inductance, Nonlinearity, and Quasiparticle Dynamics in Granular Aluminum Microwave Kinetic Inductance Detectors.
Valenti, F.; Henriques, F.; Catelani, G.; Maleeva, N.; Grünhaupt, L.; Von Lüpke, U.; Skacel, S. T.; Winkel, P.; Bilmes, A.; Ustinov, A. V.; Goupy, J.; Calvo, M.; Benoît, A.; Levy-Bertrand, F.; Monfardini, A.; Pop, I. M.
2019. Physical review applied, 11 (5), 054087. doi:10.1103/PhysRevApplied.11.054087
Circuit quantum electrodynamics of granular aluminum resonators.
Maleeva, N.; Grünhaupt, L.; Klein, T.; Levy-Bertrand, F.; Dupre, O.; Calvo, M.; Valenti, F.; Winkel, P.; Friedrich, F.; Wernsdorfer, W.; Ustinov, A. V.; Rotzinger, H.; Monfardini, A.; Fistul, M. V.; Pop, I. M.
2018. Nature Communications, 9, Article: 3889. doi:10.1038/s41467-018-06386-9VolltextVolltext der Publikation als PDF-Dokument
Tunable ohmic environment using Josephson junction chains.
Rastelli, G.; Pop, I. M.
2018. Physical review / B, 97 (20), Art.-Nr.: 205429. doi:10.1103/PhysRevB.97.205429
Simultaneous Monitoring of Fluxonium Qubits in a Waveguide.
Kou, A.; Smith, W. C.; Vool, U.; Pop, I. M.; Sliwa, K. M.; Hatridge, M.; Frunzio, L.; Devoret, M. H.
2018. Physical review applied, 9 (6), Art.-Nr. 064022–1. doi:10.1103/PhysRevApplied.9.064022
Fluxon-based quantum simulation in circuit QED.
Petrescu, A.; Türeci, H. E.; Ustinov, A. V.; Pop, I. M.
2018. Physical review / B, 98 (17), Art.Nr. 174505. doi:10.1103/PhysRevB.98.174505
Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum.
Grünhaupt, L.; Maleeva, N.; Skacel, S. T.; Calvo, M.; Levy-Bertrand, F.; Ustinov, A. V.; Rotzinger, H.; Monfardini, A.; Catelani, G.; Pop, I. M.
2018. Physical review letters, 121 (11), 117001. doi:10.1103/PhysRevLett.121.117001
Driving Forbidden Transitions in the Fluxonium Artificial Atom.
Vool, U.; Kou, A.; Smith, W. C.; Frattini, N. E.; Serniak, K.; Reinhold, P.; Pop, I. M.; Shankar, S.; Frunzio, L.; Girvin, S. M.; Devoret, M. H.
2018. Physical review applied, 9 (5), 054046. doi:10.1103/PhysRevApplied.9.054046
Bistability in a mesoscopic Josephson junction array resonator.
Muppalla, P. R.; Gargiulo, O.; Mirzaei, S. I.; Venkatesh, B. P.; Juan, M. L.; Grünhaupt, L.; Pop, I. M.; Kirchmair, G.
2018. Physical review / B, 97 (2), Art.Nr. 024518. doi:10.1103/PhysRevB.97.024518
Inductively shunted transmon qubit with tunable transverse and longitudinal coupling.
Richer, S.; Maleeva, N.; Skacel, S. T.; Pop, I. M.; DiVincenzo, D.
2017. Physical review / B, 96 (17), Art.Nr. 174520. doi:10.1103/PhysRevB.96.174520
An argon ion beam milling process for native AlOₓ layers enabling coherent superconducting contacts.
Grünhaupt, L.; Lüpke, U. von; Gusenkova, D.; Skacel, S. T.; Maleeva, N.; Schlör, S.; Bilmes, A.; Rotzinger, H.; Ustinov, A. V.; Weides, M.; Pop, I. M.
2017. Applied physics letters, 111 (7), Art. Nr. 072601. doi:10.1063/1.4990491
Quantization of inductively shunted superconducting circuits.
Smith, W. C.; Kou, A.; Vool, U.; Pop, I. M.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.
2016. Physical review / B, 94 (14), 144507. doi:10.1103/PhysRevB.94.144507
Planar Multilayer Circuit Quantum Electrodynamics.
Minev, Z. K.; Serniak, K.; Pop, I. M.; Leghtas, Z.; Sliwa, K. M.; Hatridge, M. J.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.
2016. Physical Review Applied, 5 (4), 044021. doi:10.1103/PhysRevApplied.5.044021