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We introduce an iterative method to search for time-optimal Hamiltonians that drive a quantum system between two arbitrary, and in general mixed, quantum states. The method is based on the idea of progressively improving the efficiency of…

Quantum Physics · Physics 2019-12-25 Francesco Campaioli , William Sloan , Kavan Modi , Felix Alexander Pollock

Locality is a fundamental feature of many physical time evolutions. Assumptions on locality and related structural properties also underlie recently proposed procedures for learning an unknown Hamiltonian from access to the induced time…

Quantum Physics · Physics 2026-01-21 Andreas Bluhm , Matthias C. Caro , Aadil Oufkir

We describe a novel algorithm that learns a Hamiltonian from local expectations of its Gibbs state using the free energy variational principle. The algorithm avoids the need to compute the free energy directly, instead using efficient…

Quantum Physics · Physics 2024-09-25 Adam Artymowicz

We describe a simple method for simulating time-independent Hamiltonian $H$ that could be decomposed as $H = \sum_{i=1}^m H_i$ where each $H_i$ can be efficiently simulated. Approaches relying on product formula generally work by splitting…

Quantum Physics · Physics 2024-10-22 Nhat A. Nghiem

Implementing the time evolution under a desired target Hamiltonian is critical for various applications in quantum science. Due to the exponential increase in the number of parameters with system size and experimental imperfections, this…

Quantum Physics · Physics 2025-12-11 Pascal Baßler , Markus Heinrich , Martin Kliesch

The reduction of Hamiltonian systems aims to build smaller reduced models, valid over a certain range of time and parameters, in order to reduce computing time. By maintaining the Hamiltonian structure in the reduced model, certain…

Numerical Analysis · Mathematics 2024-09-17 Raphaël Côte , Emmanuel Franck , Laurent Navoret , Guillaume Steimer , Vincent Vigon

We propose an efficient quantum algorithm for simulating the dynamics of general Hamiltonian systems. Our technique is based on a power series expansion of the time-evolution operator in its off-diagonal terms. The expansion decouples the…

Quantum Physics · Physics 2021-06-22 Amir Kalev , Itay Hen

Hamiltonian learning is a cornerstone for advancing accurate many-body simulations, improving quantum device performance, and enabling quantum-enhanced sensing. Existing readily deployable quantum metrology techniques primarily focus on…

Quantum Physics · Physics 2025-10-10 Suying Liu , Xiaodi Wu , Murphy Yuezhen Niu

We present a numerical method to simulate the time evolution, according to a Hamiltonian made of local interactions, of quantum spin chains and systems alike. The efficiency of the scheme depends on the amount of the entanglement involved…

Quantum Physics · Physics 2009-11-10 G. Vidal

We study the problem of learning the Hamiltonian of a quantum many-body system given samples from its Gibbs (thermal) state. The classical analog of this problem, known as learning graphical models or Boltzmann machines, is a well-studied…

Quantum Physics · Physics 2021-05-26 Anurag Anshu , Srinivasan Arunachalam , Tomotaka Kuwahara , Mehdi Soleimanifar

This paper proposes Hamiltonian Learning, a novel unified framework for learning with neural networks "over time", i.e., from a possibly infinite stream of data, in an online manner, without having access to future information. Existing…

Machine Learning · Computer Science 2024-09-19 Stefano Melacci , Alessandro Betti , Michele Casoni , Tommaso Guidi , Matteo Tiezzi , Marco Gori

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…

Schr\"odinger's equation serves as a fundamental component in characterizing quantum systems, wherein both quantum state tomography and Hamiltonian learning are instrumental in comprehending and interpreting quantum systems. While numerous…

Quantum Physics · Physics 2024-01-25 Zheng An , Jiahui Wu , Muchun Yang , D. L. Zhou , Bei Zeng

We propose a scheme for inverse engineering control in open quantum systems. Starting from an undetermined time evolution operator, a time-dependent Hamiltonian is derived in order to guide the system to attain an arbitrary target state at…

Quantum Physics · Physics 2015-06-16 Jun Jing , Lian-Ao Wu , Marcelo S. Sarandy , J. Gonzalo Muga

In this work, we initiate the study of Hamiltonian learning for positive temperature bosonic Gaussian states, the quantum generalization of the widely studied problem of learning Gaussian graphical models. We obtain efficient protocols,…

Quantum Physics · Physics 2025-04-08 Marco Fanizza , Cambyse Rouzé , Daniel Stilck França

We present a low-space overhead simulation algorithm based on the truncated Dyson series for time-dependent quantum dynamics. This algorithm is applied to simulating time-independent Hamiltonians by transitioning to the interaction picture,…

Quantum Physics · Physics 2019-06-07 Guang Hao Low , Nathan Wiebe

Quantum simulators with hundreds of qubits and engineerable Hamiltonians have the potential to explore quantum many-body models that are intractable for classical computers. However, learning the simulated Hamiltonian, a prerequisite for…

Quantum process characterization is a fundamental task in quantum information processing, yet conventional methods, such as quantum process tomography, require prohibitive resources and lack scalability. Here, we introduce an efficient…

Quantum Physics · Physics 2025-04-11 Yusen Wu , Yukun Zhang , Chuan Wang , Xiao Yuan

We develop a protocol for learning a class of interacting bosonic Hamiltonians from dynamics with Heisenberg-limited scaling. For Hamiltonians with an underlying bounded-degree graph structure, we can learn all parameters with root mean…

Quantum Physics · Physics 2023-07-11 Haoya Li , Yu Tong , Hongkang Ni , Tuvia Gefen , Lexing Ying

A quantum state for being an eigenstate of some local Hamiltonian should be constraint by zero energy variance and consequently, the constraint is rather strong that a single eigenstate may uniquely determine the Hamiltonian. For…

Quantum Physics · Physics 2024-12-17 Xu-Dan Xie , Zheng-Yuan Xue , Dan-Bo Zhang