Tunable impedance matching for Josephson junction reflection amplifier

Visa Vesterinen, Juha Hassel, Heikki Seppä

    Research output: Contribution to journalArticleScientificpeer-review

    3 Citations (Scopus)


    It has been recently demonstrated that a single Josephson junction with a properly engineered impedance environment can be used as a reflection amplifier approaching the quantum limit at microwave frequencies. In this article the authors describe an improved microwave setup for such a device. Voltage-tunable capacitors enable precise impedance matching across a wide range of operating points. Also, a branch-line coupler instead of a microwave circulator is used for the separation of the input and the output signals to make the system more compact and affordable. Furthermore, a custom-designed bias tee is introduced. The authors present characterization results of individual components as well as of the complete system. In particular, noise spectroscopy is used to study amplifier stability as a function of input matching.
    Original languageEnglish
    JournalIEEE Transactions on Applied Superconductivity
    Issue number3
    Publication statusPublished - 2013
    MoE publication typeA1 Journal article-refereed
    EventApplied Superconductivity Conference, ASC 2012 - Portland, United States
    Duration: 7 Oct 201212 Oct 2012


    • Impedance matching
    • Josephson effect
    • microwave amplifiers


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