Trevor Chistolini

Performance of Superconducting Resonators Suspended on SiN Membranes

  1. Trevor Chistolini,
  2. Kyunghoon Lee,
  3. Archan Banerjee,
  4. Mohammed Alghadeer,
  5. Christian Jünger,
  6. M. Virginia P. Altoé,
  7. Chengyu Song,
  8. Sudi Chen,
  9. Feng Wang,
  10. David I. Santiago,
  11. and Irfan Siddiqi
Correlated errors in superconducting circuits due to nonequilibrium quasiparticles are a notable concern in efforts to achieve fault tolerant quantum computing. The propagation of quasiparticles
causing these correlated errors can potentially be mediated by phonons in the substrate. Therefore, methods that decouple devices from the substrate are possible solutions, such as isolating devices atop SiN membranes. In this work, we validate the compatibility of SiN membrane technology with high quality superconducting circuits, adding the technique to the community’s fabrication toolbox. We do so by fabricating superconducting coplanar waveguide resonators entirely atop a thin (∼110 nm) SiN layer, where the bulk Si originally supporting it has been etched away, achieving a suspended membrane where the shortest length to its thickness yields an aspect ratio of approximately 7.4×103. We compare these membrane resonators to on-substrate resonators on the same chip, finding similar internal quality factors ∼105 at single photon levels. Furthermore, we confirm that these membranes do not adversely affect the resonator thermalization rate. With these important benchmarks validated, this technique can be extended to qubits.
arxiv pdf

Scalable High-Performance Fluxonium Quantum Processor

  1. Long B. Nguyen,
  2. Gerwin Koolstra,
  3. Yosep Kim,
  4. Alexis Morvan,
  5. Trevor Chistolini,
  6. Shraddha Singh,
  7. Konstantin N. Nesterov,
  8. Christian Jünger,
  9. Larry Chen,
  10. Zahra Pedramrazi,
  11. Bradley K. Mitchell,
  12. John Mark Kreikebaum,
  13. Shruti Puri,
  14. David I. Santiago,
  15. and Irfan Siddiqi Singh
The technological development of hardware heading toward universal fault-tolerant quantum computation requires a large-scale processing unit with high performance. While fluxonium qubits
are promising with high coherence and large anharmonicity, their scalability has not been systematically explored. In this work, we propose a superconducting quantum information processor based on compact high-coherence fluxoniums with suppressed crosstalk, reduced design complexity, improved operational efficiency, high-fidelity gates, and resistance to parameter fluctuations. In this architecture, the qubits are readout dispersively using individual resonators connected to a common bus and manipulated via combined on-chip RF and DC control lines, both of which can be designed to have low crosstalk. A multi-path coupling approach enables exchange interactions between the high-coherence computational states and at the same time suppresses the spurious static ZZ rate, leading to fast and high-fidelity entangling gates. We numerically investigate the cross resonance controlled-NOT and the differential AC-Stark controlled-Z operations, revealing low gate error for qubit-qubit detuning bandwidth of up to 1 GHz. Our study on frequency crowding indicates high fabrication yield for quantum processors consisting of over thousands of qubits. In addition, we estimate low resource overhead to suppress logical error rate using the XZZX surface code. These results promise a scalable quantum architecture with high performance for the pursuit of universal quantum computation.
arxiv pdf