Realization of High-Fidelity CZ and ZZ -Free iSWAP Gates with a Tunable Coupler

By Youngkyu Sung, L. Ding, Jochen Braumuller, A. Vepsalainen, B. Kannan, Morten Kjaergaard, A. Greene, G. Samach, C. McNally, David K. Kim and 7 more. 2020

328 citations recorded by the source corpus.

High-fidelity two-qubit gates at scale are a key requirement to realize the full promise of quantum computation and simulation. The advent and use of coupler elements to tunably control two-qubit interactions has improved operational fidelity in many-qubit systems by reducing parasitic coupling and frequency crowding issues. Nonetheless, two-qubit gate errors still limit the capability of near-term quantum applications. The reason, in part, is the existing framework for tunable couplers based on the dispersive approximation does not fully incorporate three-body multi-level dynamics, which is essential for addressing coherent leakage to the coupler and parasitic longitudinal ($ZZ$) interactions during two-qubit gates. Here, we present a systematic approach that goes beyond the dispersive approximation to exploit the engineered level structure of the coupler and optimize its control. Using this approach, we experimentally demonstrate CZ and $ZZ$-free iSWAP gates with two-qubit interaction fidelities of $99.76 \pm 0.10$% and $99.87 \pm 0.32$%, respectively, which are close to their $T_1$ limits.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/27a2c7bce428e0e5c8df3d882b265907ba920ef1

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In Artificial Intelligence

In Atomic and Molecular Physics, and Optics

Citations in the corpus

High fidelity two-qubit gates on fluxoniums using a tunable coupler (2022, background): “[17] Youngkyu Sung, Leon Ding, Jochen Braumüller, Antti Vepsäläinen, Bharath Kannan, Morten Kjaergaard, Ami Greene, Gabriel O.”
On-demand directional microwave photon emission using waveguide quantum electrodynamics (2022, methodology): “Our device comprises of four frequency-tunable transmon qubits [55] and four tunable transmon couplers [56, 57] between each neighboring qubit pair, as shown in Fig.”
Exponential suppression of bit or phase errors with cyclic error correction (2021, methodology): “Second, we implement a 26 ns controlled-Z gate using a direct swap between the states | 11 (cid:105) and | 02 (cid:105) , similar to the gates described in [14, 34].”