| CPC G06N 10/70 (2022.01) | 20 Claims |

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1. A computer-implemented method for detecting error, the method comprising:
accessing a signal of a quantum device, the quantum device including a plurality of qubits, wherein the signal includes information about a matrix, the matrix including diagonal elements and off-diagonal elements, and wherein the off-diagonal elements of the matrix are approximately sparse;
performing randomized measurements of the off-diagonal elements of the matrix by preparing entangled Greenberger-Horne-Zeilinger states (GHZ states) on random subsets of the plurality of qubits;
recovering the matrix based on a direct measurement of the diagonal elements of the matrix; and
estimating at least one of a two-qubit correlated dephasing error or a Hamiltonian error based on the recovered matrix.
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