2016/12/23 by B. P. Lanyon, Christine Maier, C. Maier +19 · 261 citations
Computer Science · Physics and Astronomy · #Benchmark (surveying) #Condensed matter physics #Open quantum system #Physics #Quantum #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum computer #Quantum entanglement #Quantum information #Quantum many-body systems #Quantum mechanics #Quantum metrology #Quantum sensor #Quantum simulator #Quantum state #Quantum system #Quantum technology #Quantum tomography #Qubit #Spins #Statistical physics #quant-ph
paper · pdf · doi:10.1038/nphys4244
published in Nature Physics 13(12), 1158-1162 (Nature Portfolio) · 5 pages of main text with 4 figures, 40 additional pages of supplementary material
arxiv created 2016/12/23 · openalex publication_date 2017/09/04 · arxiv updated 2019/01/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Quantum state tomography (QST) is the gold standard technique for obtaining an estimate for the state of small quantum systems in the laboratory. Its application to systems with more than a few constituents (e.g. particles) soon becomes impractical as the effort required grows exponentially in the number of constituents. Developing more efficient techniques is particularly pressing as precisely-controllable quantum systems that are well beyond the reach of QST are emerging in laboratories. Motivated by this, there is a considerable ongoing effort to develop new characterisation tools for quantum many-body systems. Here we demonstrate Matrix Product State (MPS) tomography, which is theoretically proven to allow the states of a broad class of quantum systems to be accurately estimated with an effort that increases efficiently with constituent number. We first prove that this broad class includes the out-of-equilbrium states produced by 1D systems with finite-range interactions, up to any fixed point in time. We then use the technique to reconstruct the dynamical state of a trapped-ion quantum simulator comprising up to 14 entangled spins (qubits): a size far beyond the reach of QST. Our results reveal the dynamical growth of entanglement and description complexity as correlations spread out during a quench: a necessary condition for future beyond-classical performance. MPS tomography should find widespread use to study large quantum many-body systems and to benchmark and verify quantum simulators and computers.