Zhang J, Cong S, Ling Q, Li K. An Efficient and Fast Quantum State Estimator With Sparse Disturbance.
IEEE TRANSACTIONS ON CYBERNETICS 2019;
49:2546-2555. [PMID:
29994018 DOI:
10.1109/tcyb.2018.2828498]
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Abstract
A pure or nearly pure quantum state can be described as a low-rank density matrix, which is a positive semidefinite and unit-trace Hermitian. We consider the problem of recovering such a low-rank density matrix contaminated by sparse components, from a small set of linear measurements. This quantum state estimation task can be formulated as a robust principal component analysis (RPCA) problem subject to positive semidefinite and unit-trace Hermitian constraints. We propose an efficient and fast inexact alternating direction method of multipliers (I-ADMM), in which the subproblems are solved inexactly and hence have closed-form solutions. We prove global convergence of the proposed I-ADMM, and the theoretical result provides a guideline for parameter setting. Numerical experiments show that the proposed I-ADMM can recover state density matrices of 5 qubits on a laptop in 0.69 s, with 6 ×10-4 accuracy (99.38% fidelity) using 30% compressive sensing measurements, which outperforms existing algorithms.
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