Exceptional points in tunable superconducting resonators

Matti Partanen (Corresponding Author), Jan Goetz, Kuan Yen Tan, Kassius Kohvakka, Vasilii Sevriuk, Russell E. Lake, Roope Kokkoniemi, Joni Ikonen, Dibyendu Hazra, Akseli Mäkinen, Eric Hyyppä, Leif Grönberg, Visa Vesterinen, Matti Silveri, Mikko Möttönen (Corresponding Author)

    Research output: Contribution to journalArticleScientificpeer-review

    38 Citations (Scopus)


    Superconducting quantum circuits are potential candidates to realize a large-scale quantum computer. The envisioned large density of integrated components, however, requires a proper thermal management and control of dissipation. To this end, it is advantageous to utilize tunable dissipation channels and to exploit the optimized heat flow at exceptional points (EPs). Here, we experimentally realize an EP in a superconducting microwave circuit consisting of two resonators. The EP is a singularity point of the effective Hamiltonian, and corresponds to critical damping with the most efficient heat transfer between the resonators without back and forth oscillation of energy. We observe a crossover from underdamped to overdamped coupling across the EP by utilizing photon-assisted tunneling as an in situ tunable dissipative element in one of the resonators. These methods can be used to obtain fast dissipation, for example, for initializing qubits to their ground states. In addition, these results pave the way for thorough investigation of parity-time symmetry and the spontaneous symmetry breaking at the EP in superconducting quantum circuits operating at the level of single energy quanta.
    Original languageEnglish
    Article number134505
    JournalPhysical Review B
    Issue number13
    Publication statusPublished - 7 Oct 2019
    MoE publication typeA1 Journal article-refereed


    We acknowledge the funding from the European Research Council under Consolidator Grant No. 681311 (QUESS), and Marie Skłodowska-Curie Grant No. 795159, the Academy of Finland through its Centres of Excellence Program (Projects No. 312300 and No. 312059) and Grants No. 265675, No. 305237, No. 305306, No. 308161, No. 312300, No. 314302, and No. 316551), the European Union via the Quantum Flagship project QMiCS (Grant No. 820505), the Vilho, Yrjö and Kalle Väisälä Foundation, the Technology Industries of Finland Centennial Foundation, the Jane and Aatos Erkko Foundation, the Alfred Kordelin Foundation, and the Emil Aaltonen Foundation.


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