Ben Scharmann

Modular Superconducting Qubit Architecture with a Multi-chip Tunable Coupler

  1. Mark Field,
  2. Angela Q. Chen,
  3. Ben Scharmann,
  4. Eyob A. Sete,
  5. Feyza Oruc,
  6. Kim Vu,
  7. Valentin Kosenko,
  8. Joshua Y. Mutus,
  9. Stefano Poletto,
  10. and Andrew Bestwick
We use a floating tunable coupler to mediate interactions between qubits on separate chips to build a modular architecture. We demonstrate three different designs of multi-chip tunable
couplers using vacuum gap capacitors or superconducting indium bump bonds to connect the coupler to a microwave line on a common substrate and then connect to the qubit on the next chip. We show that the zero-coupling condition between qubits on separate chips can be achieved in each design and that the relaxation rates for the coupler and qubits are not noticeably affected by the extra circuit elements. Finally, we demonstrate two-qubit gate operations with fidelity at the same level as qubits with a tunable coupler on a single chip. Using one or more indium bonds does not degrade qubit coherence or impact the performance of two-qubit gates.
arxiv pdf

Entanglement Across Separate Silicon Dies in a Modular Superconducting Qubit Device

  1. Alysson Gold,
  2. JP Paquette,
  3. Anna Stockklauser,
  4. Matthew J. Reagor,
  5. M. Sohaib Alam,
  6. Andrew Bestwick,
  7. Nicolas Didier,
  8. Ani Nersisyan,
  9. Feyza Oruc,
  10. Armin Razavi,
  11. Ben Scharmann,
  12. Eyob A. Sete,
  13. Biswajit Sur,
  14. Davide Venturelli,
  15. Cody James Winkleblack,
  16. Filip Wudarski,
  17. Mike Harburn,
  18. and Chad Rigetti
Assembling future large-scale quantum computers out of smaller, specialized modules promises to simplify a number of formidable science and engineering challenges. One of the primary
challenges in developing a modular architecture is in engineering high fidelity, low-latency quantum interconnects between modules. Here we demonstrate a modular solid state architecture with deterministic inter-module coupling between four physically separate, interchangeable superconducting qubit integrated circuits, achieving two-qubit gate fidelities as high as 99.1±0.5\% and 98.3±0.3\% for iSWAP and CZ entangling gates, respectively. The quality of the inter-module entanglement is further confirmed by a demonstration of Bell-inequality violation for disjoint pairs of entangled qubits across the four separate silicon dies. Having proven out the fundamental building blocks, this work provides the technological foundations for a modular quantum processor: technology which will accelerate near-term experimental efforts and open up new paths to the fault-tolerant era for solid state qubit architectures.
arxiv pdf