David van Zanten

Postdoc, Center for Quantum Devices, Niels Bohr Institute

Putting the gate-tunable Josephson inductance to use in SAG based Josephson junction arrays.

The inductance of Josephson junctions (JJ) is a rather exceptional attribute and is used in a broad range of superconducting circuits. For example, the unbiased inductance is rather large compared to conventional coplanar waveguide resonators, which makes JJ ideal elements in high impedance resonators. On the other hand, the strong nonlinearity makes JJ very suitable for (traveling wave) parametric amplifiers, in which the junctions are strongly AC driven.

Conventional application often use Al/Al2O3 technology to make JJs. Such junctions have many weakly transmitting channels, which limits the non-linearity. Recent advances in hybrid semiconductor-superconductor material have produced JJs with few channels of tunable transmission. It is expected that this type of JJ can produce 1) much larger non-linearity and 2) resonators with tunable impedance/frequency.

In this (rather unusual) talk I will propose a logical sequence of experiments with JJ arrays, each exploiting the properties of proximitized JJ. I will start with experiments with short chains (N<10)1,2, after which I’ll address experiments in which JJ arrays are used as resonators3–8. Finally, I will cover experiments in which JJ arrays are used as non-linear transmission lines9,10.

The project is in a very early stage, and no new experimental results will be shown. However, I hope this talk will inspire and trigger a discussion about putting gate tunable JJ arrays to use. The referenced papers scan be found in qdev dropbox. 

  1. Siddiqi, I. et al. Direct Observation of Dynamical Bifurcation between Two Driven Oscillation States of a Josephson Junction. Phys. Rev. Lett. 94, 027005 (2005).
  2. Stehlik, J. et al. Fast Charge Sensing of a Cavity-Coupled Double Quantum Dot Using a Josephson Parametric Amplifier. Phys. Rev. Appl. 4, 014018 (2015).
  3. Stockklauser, A. et al. Strong Coupling Cavity QED with Gate-Defined Double Quantum Dots Enabled by a High Impedance Resonator. Phys. Rev. X 7, 011030 (2017).
  4. Masluk, N. A., Pop, I. M., Kamal, A., Minev, Z. K. & Devoret, M. H. Microwave Characterization of Josephson Junction Arrays: Implementing a Low Loss Superinductance. Phys. Rev. Lett. 109, 137002 (2012).
  5. Weißl, T. et al. Bloch band dynamics of a Josephson junction in an inductive environment. Phys. Rev. B 91, 014507 (2015).
  6. Rolland, C. et al. Antibunched photons emitted by a dc-biased Josephson junction. 1, (2018).
  7. Hofheinz, M. et al. Bright Side of the Coulomb Blockade. Phys. Rev. Lett. 106, 217005 (2011).
  8. Kuzmin, R., Mencia, R., Grabon, N., Mehta, N. & Manucharyan, V. E. Quantum electrodynamics of a superconductor-insulator phase transition. 3, 1–6 (2018).
  9. Macklin, C. et al. A near-quantum-limited Josephson traveling-wave parametric amplifier. Science (80-. ). 350, 307–310 (2015).
  10. White, T. C. et al. Traveling wave parametric amplifier with Josephson junctions using minimal resonator phase matching. Appl. Phys. Lett. 106, 242601 (2015).