Gate-based quantum computers typically encode and process information in two-dimensional units called qubits. Using d-dimensional qudits instead may offer intrinsic advantages, including more efficient circuit synthesis, problem-tailored encodings and embedded error correction. In this work, we design a superconducting qudit-based quantum processor wherein the logical space of transmon qubits is extended to higher-excited levels. We propose a universal gate set featuring a two-qudit cross-resonance entangling gate, for which we predict fidelities beyond 99% in the d = 4 case of ququarts with realistic experimental parameters. Furthermore, we present a decomposition routine that compiles general qudit unitaries into these elementary gates, requiring fewer entangling gates than qubit alternatives. As proof-of-concept applications, we numerically demonstrate the synthesis of SU(16) gates for noisy quantum hardware and an embedded error-correction sequence that encodes a qubit memory in a transmon ququart to protect against pure dephasing noise. We conclude that universal qudit control-a valuable extension to the operational toolbox of superconducting quantum information processing-is within reach of current transmon-based architectures and has applications to near-term and long-term hardware.

Universal Qudit Gate Synthesis for Transmons / Fischer, L. E.; Chiesa, A.; Tacchino, F.; Egger, D. J.; Carretta, S.; Tavernelli, I.. - In: PRX QUANTUM. - ISSN 2691-3399. - 4:3(2023). [10.1103/PRXQuantum.4.030327]

Universal Qudit Gate Synthesis for Transmons

Chiesa A.;Carretta S.;
2023-01-01

Abstract

Gate-based quantum computers typically encode and process information in two-dimensional units called qubits. Using d-dimensional qudits instead may offer intrinsic advantages, including more efficient circuit synthesis, problem-tailored encodings and embedded error correction. In this work, we design a superconducting qudit-based quantum processor wherein the logical space of transmon qubits is extended to higher-excited levels. We propose a universal gate set featuring a two-qudit cross-resonance entangling gate, for which we predict fidelities beyond 99% in the d = 4 case of ququarts with realistic experimental parameters. Furthermore, we present a decomposition routine that compiles general qudit unitaries into these elementary gates, requiring fewer entangling gates than qubit alternatives. As proof-of-concept applications, we numerically demonstrate the synthesis of SU(16) gates for noisy quantum hardware and an embedded error-correction sequence that encodes a qubit memory in a transmon ququart to protect against pure dephasing noise. We conclude that universal qudit control-a valuable extension to the operational toolbox of superconducting quantum information processing-is within reach of current transmon-based architectures and has applications to near-term and long-term hardware.
2023
Universal Qudit Gate Synthesis for Transmons / Fischer, L. E.; Chiesa, A.; Tacchino, F.; Egger, D. J.; Carretta, S.; Tavernelli, I.. - In: PRX QUANTUM. - ISSN 2691-3399. - 4:3(2023). [10.1103/PRXQuantum.4.030327]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2968497
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