Quantum Process Tomography on Cloud-accessible Quantum Computing Platforms

Special quantum circuits make it possible to collect experimental data to study the dynamics of quantum processor qubits [1]. The harmonic inversion method restores a set of eigenvalues that form a diagram qualitatively similar to the full spectrum of the open quantum system Liouvillian [2]. The Lindblad tomography method [3] evaluates initial state preparation and measurement error (SPAM), Kraus operators, non-Markovian measure, Hamiltonian and Lindblad operators describing the evolution of an open quantum system. We estimated SPAM errors, reconstructed the evolution using Kraus operators for discrete times, and estimated the non-Markovianity of the first qubits of the OriginQ Wuyuan 1 (Origin Quantum Cloud) and ibmq_belem (IBM Quantum Computing) quantum computers. The obtained results demonstrate the comparability of the platforms parameters and a low degree of non-Markovian behavior. The nearest future challenges are related to describing the observed processes in the form of the time-independent Lindblad equation along with the experiments involving two-qubit interaction.