High-Coherence Kerr-Cat Qubit in 2D Architecture

Authors

Ahmed Hajr, University of California - Berkeley
Bingcheng Qing, University of California - Berkeley
Ke Wang, University of California - Berkeley
Gerwin Koolstra, University of California - Berkeley
Zahra Pedramrazi, University of California - Berkeley
Ziqi Kang, University of California - Berkeley
Larry Chen, University of California - Berkeley
Long B. Nguyen, University of California - Berkeley
Christian Jünger, University of California - Berkeley
Noah Goss, University of California - Berkeley
Irwin Huang, University of Rochester
Bibek Bhandari, Chapman University
Nicholas E. Frattini, Yale University
Shruti Puri, Yale University
Justin Dressel, Chapman UniversityFollow
Andrew N. Jordan, Chapman UniversityFollow
David I. Santiago, Lawrence Berkeley National Laboratory,
Irfan Siddiqi, University of California - Berkeley

Document Type

Article

Publication Date

11-20-2024

Abstract

The Kerr-cat qubit is a bosonic qubit in which multiphoton Schrödinger cat states are stabilized by applying a two-photon drive to an oscillator with a Kerr nonlinearity. The suppressed bit-flip rate with increasing cat size makes this qubit a promising candidate to implement quantum error correction codes tailored for noise-biased qubits. However, achieving strong light-matter interactions necessary for stabilizing and controlling this qubit has traditionally required strong microwave drives that heat the qubit and degrade its performance. In contrast, increasing the coupling to the drive port removes the need for strong drives at the expense of large Purcell decay. By integrating an effective band-block filter on chip, we overcome this trade-off and realize a Kerr-cat qubit in a scalable 2D superconducting circuit with high coherence. This filter provides 30 dB of isolation at the qubit frequency with negligible attenuation at the frequencies required for stabilization and readout. We experimentally demonstrate quantum nondemolition readout fidelity of 99.6% for a cat with eight photons. Also, to have high-fidelity universal control over this qubit, we combine fast Rabi oscillations with a new demonstration of the 𝑋⁢(𝜋/2) gate through phase modulation of the stabilization drive. Finally, the lifetime in this architecture is examined as a function of the cat size of up to ten photons in the oscillator, achieving a bit-flip time higher than 1 ms and only a linear increase in the phase-flip rate, in good agreement with the theoretical analysis of the circuit. Our qubit shows promise as a building block for fault-tolerant quantum processors with a small footprint.

Comments

This article was originally published in Physical Review X, volume 14, in 2024. https://doi.org/10.1103/PhysRevX.14.041049

Recommended Citation

A. Hajr, B. Qing, K. Wang, G. Koolstra, Z. Pedramrazi, Z. Kang, L. Chen, L. B. Nguyen, C. Jünger, N. Goss, I. Huang, B. Bhandari, N. E. Frattini, S. Puri, J. Dressel, A. N. Jordan, D. I. Santiago, and I. Siddiqi, High-coherence Kerr-cat qubit in 2D architecture, Phys. Rev. X 14, 041049 (2024). https://doi.org/10.1103/PhysRevX.14.041049

Peer Reviewed

1

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.