Abstract
The exploration of highly connected networks of qubits is invaluable for implementing various quantum algorithms and simulations, as it allows for entangling qubits with reduced circuit depth. Here, we demonstrate a multiqubit sideband tone-assisted Rabi-driven gate. Our scheme is inspired by the ion-qubit Mølmer-Sørensen gate and is mediated by a shared photonic mode and Rabi-driven superconducting qubits, which relaxes restrictions on qubit frequencies during fabrication and supports scalability. We achieve a two-qubit gate with a maximum state fidelity of 95% in 310 ns, a three-qubit gate with a state fidelity of 90.5% in 217 ns, and a four-qubit gate with a state fidelity of 66% in 200 ns. Furthermore, we develop a model of the gate that shows that the four-qubit gate is limited by shared resonator losses and the spread of qubit-resonator couplings, which must be addressed to reach high-fidelity operations.
7 More- Received 17 July 2022
- Accepted 24 October 2022
- Corrected 20 December 2022
DOI:https://doi.org/10.1103/PRXQuantum.3.040322
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Corrections
20 December 2022
Correction: An incorrect version of the abstract was inserted during the proof production cycle and has been set right.
Popular Summary
In harnessing quantum advantages for computation, there is a need for developing high-fidelity operations on qubits. An algorithm can be broken down into single-qubit operations and two-qubit entangling gates. However, as the leading quantum processors today are limited to 50–100 qubits and each qubit is sensitive to decoherence noise [often referred to the noisy intermediate-scale quantum (NISQ) era devices], running algorithms with a long gate depth is difficult. The generation of entanglement on three and more qubits is central for reducing the gate depth. This work demonstrates a multiqubit entangling gate for superconducting qubits on an all-to-all connected processor and draws upon the advantages of Rabi-driven qubits.
The idea of all-to-all connectivity has a long history in many-qubit platforms. It allows for easy access to any subset of qubits for an entangling operation. However, this is not the prevalent scheme for superconducting qubits, because it is difficult to provide enough space for qubits in a scalable manner while maintaining all-to-all connectivity. We use the technique of Rabi-driven qubits to eliminate the need for tunable qubits, reducing the footprint per qubit. Furthermore, the driven frame relaxes restrictions on qubit frequencies during fabrication and offers the protection of dynamical decoupling from noise. These advantages offer a feasible path toward scaling for multiqubit gates, opening up many possibilities for NISQ algorithms and simulations.