Jean Olivier Simoneau

Quantum error correction of a grid-state qubit with state preparation and measurement errors below 10−3

  1. Sara Turcotte,
  2. Lucas St-Jean,
  3. Amélie L. Pessonneaux,
  4. Ross Shillito,
  5. Bohdan Kulchytskyy,
  6. Eliott Ouellet,
  7. Jean Olivier Simoneau,
  8. Florian Hopfmueller,
  9. Matthew Hamer,
  10. Pascal Lemieux,
  11. Dany Lachance-Quirion,
  12. Baptiste Royer,
  13. and Nicholas E. Frattini
Grid state qubits offer a hardware-efficient approach to large-scale fault-tolerant quantum computing. They access the information redundancy required for quantum error correction by
exploiting the large Hilbert space naturally available in harmonic oscillators. Superconducting architectures are particularly suitable to implement grid state qubits due to their fast and high-fidelity operations. Grid states in superconducting circuits enable quantum error correction (QEC) with performance beyond break-even. However, the state preparation and measurements (SPAM) errors of grid states has been a significant limitation to computational performances. In this work, we leverage high-performance QEC to enable repeat-until-success state preparation of both cardinal and magic states of the single-mode grid-state qubit. We combine this with an improved measurement protocol that corrects for both finite-energy envelope and auxiliary qubit readout errors, and increases robustness to photon loss. Our experiments, using both techniques, achieve a combined state-preparation and measurement error below 10−3. This represents two orders-of-magnitude improvement over the state of the art, bringing this platform on par with standard SPAM error levels measured in transmon qubits.
arxiv pdf

Photocount statistics of the Josephson parametric amplifier: a question of detection

  1. Jean Olivier Simoneau,
  2. Stéphane Virally,
  3. Christian Lupien,
  4. and Bertrand Reulet
Parametric amplifiers are known to squeeze the vacuum state of the electromagnetic field, which results in predictable statistics of the photocounts at their output. However, recent
theoretical work arXiv:1112.4159 predicts a very different statistical distribution for an amplifier based on a Josephson junction. We test the hypothesis experimentally and recover the expected squeezed vacuum statistics. We explain this discrepancy by showing theoretically how the photocount statistics is dictated by the detection process, from single mode (our experiment) to multimode, fully resolved in frequency (as in arXiv:1112.4159).
arxiv pdf

Discrete photon statistics from continuous microwave measurements

  1. Stéphane Virally,
  2. Jean Olivier Simoneau,
  3. Christian Lupien,
  4. and Bertrand Reulet
Photocount statistics are an important tool for the characterization of electromagnetic fields, especially for fields with an irrelevant phase. In the microwave domain, continuous rather
than discrete measurements are the norm. Using a novel approach, we recover discrete photon statistics from the cumulants of a continuous distribution of field quadrature measurements. The use of cumulants allows the separation between the signal of interest and experimental noise. Using a parametric amplifier as the first stage of the amplification chain, we extract useful data from up to the sixth cumulant of the continuous distribution of a coherent field, hence recovering up to the third moment of the discrete statistics associated with a signal with much less than one average photon.
arxiv pdf