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An iterative algorithm for the reconstruction of an unknown quantum state from the results of incompatible measurements is proposed. It consists of Expectation-Maximization step followed by a unitary transformation of the eigenbasis of the…

Quantum Physics · Physics 2009-11-06 J. Rehacek , Z. Hradil , M. Jezek

In the remote state estimation problem, an observer tries to reconstruct the state of a dynamical system at a remote location, where no direct sensor measurements are available. The observer only has access to information sent through a…

Optimization and Control · Mathematics 2021-06-28 Christoph Kawan , Sigurdur Hafstein , Peter Giesl

Many recent tensor network algorithms apply unitary operators to parts of a tensor network in order to reduce entanglement. However, many of the previously used iterative algorithms to minimize entanglement can be slow. We introduce an…

Quantum Physics · Physics 2022-01-25 Kevin Slagle

Reconstructing Hamiltonians from local measurements is key to enabling reliable quantum simulation: both validating the implemented model, and identifying any left-over terms with sufficient precision is a problem of increasing importance.…

Quantum Physics · Physics 2024-07-09 Sourav Nandy , Markus Schmitt , Marin Bukov , Zala Lenarčič

We construct entanglement renormalization schemes which provably approximate the ground states of non-interacting fermion nearest-neighbor hopping Hamiltonians on the one-dimensional discrete line and the two-dimensional square lattice.…

Signal sampling and reconstruction is a fundamental engineering task at the heart of signal processing. The celebrated Shannon-Nyquist theorem guarantees perfect signal reconstruction from uniform samples, obtained at a rate twice the…

Signal Processing · Electrical Eng. & Systems 2020-02-19 Charilaos I. Kanatsoulis , Xiao Fu , Nicholas D. Sidiropoulos , Mehmet Akçakaya

We introduce a method for extracting meaningful entanglement measures of tensor network states in general dimensions. Current methods require the explicit reconstruction of the density matrix, which is highly demanding, or the contraction…

Strongly Correlated Electrons · Physics 2022-07-28 Noa Feldman , Augustine Kshetrimayum , Jens Eisert , Moshe Goldstein

We introduce a method for the search of parent Hamiltonians of input wave-functions based on the structure of their reduced density matrix. The two key elements of our recipe are an ansatz on the relation between reduced density matrix and…

Quantum Physics · Physics 2019-04-24 X. Turkeshi , T. Mendes-Santos , G. Giudici , M. Dalmonte

We introduce an efficient method to reconstruct the Wigner function of many-mode continuous variable systems. It is based on convex optimization with semidefinite programs, and also includes a version of the maximum entropy principle, in…

Quantum Physics · Physics 2020-02-28 Ludmila A. S. Botelho , Reinaldo O. Vianna

Learning faithful representations of quantum states is crucial to fully characterizing the variety of many-body states created on quantum processors. While various tomographic methods such as classical shadow and MPS tomography have shown…

Tensor network algorithms seek to minimize correlations to compress the classical data representing quantum states. Tensor network algorithms and similar tools---called tensor network methods---form the backbone of modern numerical methods…

Quantum Physics · Physics 2021-04-08 Andrey Kardashin , Alexey Uvarov , Jacob Biamonte

In this paper, we consider regression problems with one-hidden-layer neural networks (1NNs). We distill some properties of activation functions that lead to $\mathit{local~strong~convexity}$ in the neighborhood of the ground-truth…

Machine Learning · Computer Science 2017-06-13 Kai Zhong , Zhao Song , Prateek Jain , Peter L. Bartlett , Inderjit S. Dhillon

Reconstructing the Hamiltonian of a quantum system is an essential task for characterizing and certifying quantum processors and simulators. Existing techniques either rely on projective measurements of the system before and after coherent…

The efficient quantum state reconstruction algorithm described in [P. Six et al., Phys. Rev. A 93, 012109 (2016)] is experimentally implemented on the non-local state of two microwave cavities entangled by a circular Rydberg atom. We use…

Variational quantum algorithms (VQAs) are a broad class of algorithms with many applications in science and industry. Applying a VQA to a problem involves optimizing a parameterized quantum circuit by maximizing or minimizing a cost…

Quantum Physics · Physics 2025-06-04 Tianyi Hao , Zichang He , Ruslan Shaydulin , Marco Pistoia , Swamit Tannu

In this article we study the possibilities of recovering the structure of port-Hamiltonian systems starting from ``unlabelled'' ordinary differential equations describing mechanical systems. The algorithm we suggest solves the problem in…

Computational Engineering, Finance, and Science · Computer Science 2023-04-26 Vladimir Salnikov , Antoine Falaize , Daria Loziienko

We investigate the sample size requirement for exact recovery of a high order tensor of low rank from a subset of its entries. In the Tucker decomposition framework, we show that the Riemannian optimization algorithm with initial value…

Machine Learning · Statistics 2019-11-13 Jian-Feng Cai , Lizhang Miao , Yang Wang , Yin Xian

We propose a generalized Lanczos method to generate the many-body basis states of quantum lattice models using tensor-network states (TNS). The ground-state wave function is represented as a linear superposition composed from a set of TNS…

Strongly Correlated Electrons · Physics 2022-10-19 Rui-Zhen Huang , Hai-Jun Liao , Zhi-Yuan Liu , Hai-Dong Xie , Zhi-Yuan Xie , Hui-Hai Zhao , Jing Chen , Tao Xiang

Tensor network states are for good reasons believed to capture ground states of gapped local Hamiltonians arising in the condensed matter context, states which are in turn expected to satisfy an entanglement area law. However, the…

Quantum Physics · Physics 2017-06-28 M. Schwarz , O. Buerschaper , J. Eisert

Recovering an unknown Hamiltonian from measurements is an increasingly important task for certification of noisy quantum devices and simulators. Recent works have succeeded in recovering the Hamiltonian of an isolated quantum system with…

Quantum Physics · Physics 2019-01-24 Eyal Bairey , Itai Arad , Netanel H. Lindner