Filip Wudarski

Characterizing low-frequency qubit noise

  1. Filip Wudarski,
  2. Yaxing Zhang,
  3. Alexander Korotkov,
  4. A. G. Petukhov,
  5. and M. I. Dykman
Fluctuations of the qubit frequencies are one of the major problems to overcome on the way to scalable quantum computers. Of particular importance are fluctuations with the correlation
time that exceeds the decoherence time due to decay and dephasing by fast processes. The statistics of the fluctuations can be characterized by measuring the correlators of the outcomes of periodically repeated Ramsey measurements. This work suggests a method that allows describing qubit dynamics during repeated measurements in the presence of evolving noise. It made it possible, in particular, to evaluate the two-time correlator for the noise from two-level systems and obtain two- and three-time correlators for a Gaussian noise. The explicit expressions for the correlators are compared with simulations. A significant difference of the three-time correlators for the noise from two-level systems and for a Gaussian noise is demonstrated. Strong broadening of the distribution of the outcomes of Ramsey measurements, with a possible fine structure, is found for the data acquisition time comparable to the noise correlation time.
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