Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting a gated $\mathrm{In}\mathrm{As}$ - $\mathrm{Al}$ Josephson junction to a coplanar waveguide resonator, we demonstrate the use of a superconducting element with wideband gate tunability. We show that the resonant frequency is controlled via a gate-tunable Josephson inductance and that the nonlinearity of the $\mathrm{In}\mathrm{As}$ - $\mathrm{Al}$ junction is nondissipative as is the case with conventional ${\mathrm{Al}\mathrm{O}}_{\mathrm{x}}\text{-Al}$ junctions. As the gate voltage is decreased, the inductive participation of the junction increases up to $44\mathrm{%}$, resulting in the resonant frequency being tuned by over $2\phantom{\rule{0.2em}{0ex}}\mathrm{GHz}$ . Utilizing the wide tunability of the device, we demonstrate that two resonant modes can be adjusted such that they strongly hybridize, exhibiting an avoided-level crossing with a coupling strength of $51\phantom{\rule{0.2em}{0ex}}\mathrm{MHz}$ . Implementing such voltage-tunable resonators is the first step toward realizing wafer-scale continuous voltage control in superconducting circuits for qubit-qubit coupling, quantum limited amplifiers, and quantum memory platforms.Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting a gated $\mathrm{In}\mathrm{As}$-$\mathrm{Al}$ Josephson junction to a coplanar waveguide resonator, we demonstrate the use of a superconducting element with wideband gate tunability. We show that the resonant frequency is controlled via a gate-tunable Josephson inductance and that the nonlinearity of the $\mathrm{In}\mathrm{As}$-$\mathrm{Al}$ junction is nondissipative as is the case with conventional ${\mathrm{Al}\mathrm{O}}_{\mathrm{x}}\text{-Al}$ junctions. As the gate voltage is decreased, the inductive participation of the junction increases up to $44\mathrm{%}$, resulting in the resonant frequency being tuned by over $2\phantom{\rule{0.2em}{0ex}}\mathrm{GHz}$. Utilizing the wide tunability of the device, we demonstrate that two resonant modes can be adjusted such that they strongly hybridize, exhibiting an avoided-level crossing with a coupling strength of $51\phantom{\rule{0.2em}{0ex}}\mathrm{MHz}$. Implementing such voltage-tunable resonators is the first step toward realizing wafer-scale continuous voltage control in superconducting circuits for qubit-qubit coupling, quantum limited amplifiers, and quantum memory platforms.

arXiv:2210.02491Physical Review AppliedMar 7, 202330 citations

The tunable Josephson resonator and its application to superconducting quantum computation

Joshua Strong

Jan 1, 20090 citations

Josephson junction arrays as a variable inductor in RF circuits and tunable filters

V. K. Kaplunenko, Gerd M Fischer

We report on the investigation of the effects of the nonlinear inductance of huge Josephson junction arrays on high-quality RF circuits. The inductance of a single junction is far too small for use in many RF applications; however, Josephson junction stacks and especially intrinsic Josephson junctions in crystalline-layered superconductors open new opportunities. The stack inductance can be altered by changing a DC Josephson current either using an external bias current or an external magnetic field applied to a closed superconducting loop containing two stacks connected in parallel. Using stacks of Josephson junctions in the LC resonators, a tunable 4-pole, 15 MHz band-pass filter with a centre frequency at 1.1 GHz was designed. The filter was simulated in the time domain and the response was converted to the frequency domain. It was found that using an input power level of −62 dBm, corresponding to 0.5% of the junctions' critical current, a linear approximation for the stack nonlinear inductance can be used. By changing the applied magnetic field, a tuning range of 20% was demonstrated with a tuning speed of 2 µs or better. An estimate of the losses is also given. In addition, power handling up to −26 dBm is reported using increasing circuit complexity.We report on the investigation of the effects of the nonlinear inductance of huge Josephson junction arrays on high-quality RF circuits. The inductance of a single junction is far too small for use in many RF applications; however, Josephson junction stacks and especially intrinsic Josephson junctions in crystalline-layered superconductors open new opportunities. The stack inductance can be altered by changing a DC Josephson current either using an external bias current or an external magnetic field applied to a closed superconducting loop containing two stacks connected in parallel. Using stacks of Josephson junctions in the LC resonators, a tunable 4-pole, 15 MHz band-pass filter with a centre frequency at 1.1 GHz was designed. The filter was simulated in the time domain and the response was converted to the frequency domain. It was found that using an input power level of −62 dBm, corresponding to 0.5% of the junctions' critical current, a linear approximation for the stack nonlinear inductance can be used. By changing the applied magnetic field, a tuning range of 20% was demonstrated with a tuning speed of 2 µs or better. An estimate of the losses is also given. In addition, power handling up to −26 dBm is reported using increasing circuit complexity.

Superconductor Science and TechnologyFeb 19, 200417 citations

Tunable coupling between two superconducting resonators

Frank Deppe, F. Wulschner, A. Baust +7 more

Bulletin of the American Physical SocietyMar 3, 20140 citations

Low-loss tunable metamaterials using superconducting thin-film circuits with Josephson junctions

S. Butz, P. Jung, Alexey Vladimirovich Ustinov

We report on experiments with superconducting Josephson metamaterials. In such a material, conventional split ring resonators are replaced by superconducting loops that are interrupted by Josephson junctions, so called rf-SQUIDs. Like the split ring resonators, they can be seen as LCresonators that couple to the magnetic component of the incoming wave. The advantage of superconducting thin-film metamaterials is that due to the tunable intrinsic inductance of the Josephson junction, the resonance frequency of the rf-SQUID can be changed by applying an external dc magnetic field. We present experimental results that show the tunability of the resonance frequency of these devices.We report on experiments with superconducting Josephson metamaterials. In such a material, conventional split ring resonators are replaced by superconducting loops that are interrupted by Josephson junctions, so called rf-SQUIDs. Like the split ring resonators, they can be seen as LCresonators that couple to the magnetic component of the incoming wave. The advantage of superconducting thin-film metamaterials is that due to the tunable intrinsic inductance of the Josephson junction, the resonance frequency of the rf-SQUID can be changed by applying an external dc magnetic field. We present experimental results that show the tunability of the resonance frequency of these devices.

Jan 1, 20120 citations

Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting a gated

\mathrm{In}\mathrm{As}

\mathrm{Al}

Josephson junction to a coplanar waveguide resonator, we demonstrate the use of a superconducting element with wideband gate tunability. We show that the resonant frequency is controlled via a gate-tunable Josephson inductance and that the nonlinearity of the

\mathrm{In}\mathrm{As}

\mathrm{Al}

junction is nondissipative as is the case with conventional

{\mathrm{Al}\mathrm{O}}_{\mathrm{x}}\text{-Al}

junctions. As the gate voltage is decreased, the inductive participation of the junction increases up to $44\mathrm{%}$, resulting in the resonant frequency being tuned by over

2\phantom{\rule{0.2em}{0ex}}\mathrm{GHz}

. Utilizing the wide tunability of the device, we demonstrate that two resonant modes can be adjusted such that they strongly hybridize, exhibiting an avoided-level crossing with a coupling strength of

51\phantom{\rule{0.2em}{0ex}}\mathrm{MHz}

. Implementing such voltage-tunable resonators is the first step toward realizing wafer-scale continuous voltage control in superconducting circuits for qubit-qubit coupling, quantum limited amplifiers, and quantum memory platforms.