Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                

Fluxon Readout of a Superconducting Qubit

Kirill G. Fedorov, Anastasia V. Shcherbakova, Michael J. Wolf, Detlef Beckmann, and Alexey V. Ustinov
Phys. Rev. Lett. 112, 160502 – Published 25 April 2014
PDFHTMLExport Citation
Abstract
Authors
Article Text
  • ACKNOWLEDGEMENTS
    • Supplemental Material
    References

    Abstract

    An experiment demonstrating a link between classical single-flux quantum digital logic and a superconducting quantum circuit is reported. We implement coupling between a moving Josephson vortex (fluxon) and a flux qubit by reading out of a state of the flux qubit through a frequency shift of the fluxon oscillations in an annular Josephson junction. The energy spectrum of the flux qubit is measured using this technique. The implemented hybrid scheme opens an opportunity to readout quantum states of superconducting qubits with the classical fluxon logic circuits.

    • Figure
    • Figure
    • Figure
    • Figure
    • Received 18 November 2013

    DOI:https://doi.org/10.1103/PhysRevLett.112.160502

    © 2014 American Physical Society

    Authors & Affiliations

    Kirill G. Fedorov1,2,*, Anastasia V. Shcherbakova1, Michael J. Wolf3, Detlef Beckmann3, and Alexey V. Ustinov1,2,4,†

    • 1Physikalisches Institut and DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
    • 2National University of Science and Technology MISIS, Leninsky prospekt 4, Moscow 119049, Russia
    • 3Institute of Nanotechnology, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
    • 4Russian Quantum Center, 100 Novaya Street, Skolkovo, Moscow region 143025, Russia

    • *Present address: Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany. kirill.fedorov@wmi.badw.de
    • †ustinov@kit.edu

    Article Text (Subscription Required)

    Click to Expand

    Supplemental Material (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 112, Iss. 16 — 25 April 2014

    Reuse & Permissions
    Access Options
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      An annular Josephson junction coupled to a flux qubit. The junction is homogeneously biased by an external current source Ib. The flux qubit is controlled by a dc control line current ICL and a microwave signal Iac at the frequency of νe. The purple lines schematically show the flow of the electrical currents. The fluxon equilibrium oscillation frequency ν0 is shifted by an amount δν due to fluxon scattering on the current dipole produced by a flux qubit. Microwave radiation from the fluxon is picked up by a capacitively coupled microstrip antenna and later fed to a cryogenic amplifier (not shown).

      Reuse & Permissions
    • Figure 2
      Figure 2

      (a) The theoretical persistent current Ip of the ground state of the flux qubit versus magnetic frustration (black line) calculated for our flux qubit parameters. The red line shows the expected fluxon frequency shift in kHz for γ=0.4 and μ=0.05. (b) The experimentally measured modulation of the fluxon oscillation frequency due to the coupling to the flux qubit. Black dots show the measured mean frequency of fluxon oscillations. Every point consists of 100 averages; bias is γ=0.39. The red line shows the corresponding fit.

      Reuse & Permissions
    • Figure 3
      Figure 3

      (a) The theoretically expected persistent current Ip for the ground state of the flux qubit versus magnetic flux (black line). The spikes indicate the presumed transitions to the first excited state at flux bias points corresponding to E12=14  GHz flux qubit energy splitting. The green line shows the expected persistent current Ip for the first excited state. (b) Modulation of the fluxon’s oscillation frequency due to the coupling to the qubit, measured in the power domain. Measured power P relates to the power at the fixed frequency offset +50  kHz from the fluxon mean oscillation frequency νf. Every point consists of 10 averages with video filter bandwidth of 10 Hz. The red line depicts the corresponding theory fit.

      Reuse & Permissions
    • Figure 4
      Figure 4

      Fluxon response on the microwave excitation applied to the flux qubit. Color scale corresponds to the detected power. Measured power P relates to the power at the fixed frequency offset +50  kHz from the fluxon mean oscillation frequency νf. Every point consists of 10 averages with video filter bandwidth of 1 Hz. The flux qubit spectrum can be clearly seen as the red-yellow curved trace. The black dashed line depicts the corresponding fit of the flux qubit.

      Reuse & Permissions
    ×

    Sign up to receive regular email alerts from Physical Review Letters

    Log In

    Cancel
    ×

    Search

    Article Lookup

    Paste a citation or DOI
    Enter a citation
    ×