Deterministic controlled-phase gates on remote transmon qutrits with input–output theory

Abstract

Crosstalk can degrade the fidelity of quantum operations in highly integrated quantum chips. To mitigate crosstalk and enable large-scale quantum computing (QC) with superconducting qubits (SQs), we adopt a distributed QC architecture. Using input–output theory, we propose a deterministic scheme for implementing a high-fidelity, high-efficiency controlled-phase gate between two remote superconducting transmon qutrits assisted by a flying microwave photon. Furthermore, this gate can be readily extended to a multi-target-qubit controlled-phase gate. In the scheme, a transmon qubit coupled to a double-sided superconducting transmission line resonator serves as the microwave photon emitter, and only one microwave photon is needed to run through the circuit from start to finish without being emitted and absorbed by a qubit–resonator system. To verify the feasibility of the schemes, we calculate the average fidelities and average efficiencies of the controlled-phase gate and the two-target-qubit controlled-phase gate using feasible parameters and found that both exceeded \(99.9\%\).