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We propose incorporating multi-qubit nonunitary operations in Variational Quantum Thermalizers (VQTs). VQTs are hybrid quantum-classical algorithms that generate the thermal (Gibbs) state of a given Hamiltonian, with applications in quantum…

Quantum Physics · Physics 2025-03-28 Elias Zapusek , Kristina Kirova , Walter Hahn , Michael Marthaler , Florentin Reiter

The quantum open-system simulation is an important category of quantum simulation. By simulating the thermalisation process at the zero temperature, we can solve the ground-state problem of quantum systems. To realise the open-system…

Quantum Physics · Physics 2020-01-22 Hong-Yi Su , Ying Li

We consider the problem of finding the energy minimum of a complex quantum Hamiltonian by employing a non-Markovian bath prepared in a low energy state. The energy minimization problem is thus turned into a thermodynamic cooling protocol in…

Quantum Physics · Physics 2024-03-29 Alberto Imparato , Nicholas Chancellor , Gabriele De Chiara

In the current era of noisy quantum devices, there is a need for quantum algorithms that are efficient and robust against noise. Towards this end, we introduce the projected cooling algorithm for quantum computation. The projected cooling…

The preparation of quantum Gibbs states is a fundamental challenge in quantum computing, essential for applications ranging from modeling open quantum systems to quantum machine learning. Building on the Meta-Variational Quantum Eigensolver…

Quantum Physics · Physics 2025-10-20 Ruchira V Bhat , Rahul Bhowmick , Avinash Singh , Krishna Kumar Sabapathy

We introduce a finite-time protocol that thermalizes a quantum harmonic oscillator, initially in its ground state, without requiring a macroscopic bath. The method uses a second oscillator as an effective environment and implements sudden…

Quantum Physics · Physics 2026-05-05 M. Harinarayanan , Karthik Rajeev

We derive a necessary and sufficient condition for the thermalization of a local observable in a closed quantum system which offers an alternative explanation, independent of the eigenstate thermalization hypothesis, for the thermalization…

Statistical Mechanics · Physics 2014-04-11 J. Sirker , N. P. Konstantinidis , F. Andraschko , N. Sedlmayr

We propose a method based on deep reinforcement learning that efficiently prepares a quantum many-body pure state in thermal or prethermal equilibrium. The main physical intuition underlying the method is that the information on the…

Quantum Physics · Physics 2023-01-30 Shotaro Z. Baba , Nobuyuki Yoshioka , Yuto Ashida , Takahiro Sagawa

Preparing thermal and ground states is an essential quantum algorithmic task for quantum simulation. In this work, we construct the first efficiently implementable and exactly detailed-balanced Lindbladian for Gibbs states of arbitrary…

Quantum Physics · Physics 2025-10-15 Chi-Fang Chen , Michael J. Kastoryano , András Gilyén

The preparation and computation of many properties of quantum Gibbs states is essential for algorithms such as quantum semidefinite programming and quantum Boltzmann machines. We propose a quantum algorithm that can predict $M$ linear…

Quantum Physics · Physics 2023-06-27 Luuk Coopmans , Yuta Kikuchi , Marcello Benedetti

Hamiltonian diagonalization is at the heart of understanding physical properties and practical applications of quantum systems. It is highly desired to design quantum algorithms that can speedup Hamiltonian diagonalization, especially those…

Quantum Physics · Physics 2021-07-23 Jinfeng Zeng , Chenfeng Cao , Chao Zhang , Pengxiang Xu , Bei Zeng

The simulation of low-temperature properties of many-body systems remains one of the major challenges in theoretical and experimental quantum information science. We present, and demonstrate experimentally, a universal cooling method which…

The study of thermal operations allows one to investigate the ultimate possibilities of quantum states and of nanoscale thermal machines. Whilst fairly general, these results typically do not apply to continuous variable systems and do not…

Quantum Physics · Physics 2020-01-22 A. Serafini , M. Lostaglio , S. Longden , U. Shackerley-Bennett , C. -Y. Hsieh , G. Adesso

We present a quantum algorithm for the microcanonical thermal pure quantum (TPQ) method, which has an advantage in evaluating thermodynamic quantities at finite temperatures, by combining with some recently developed techniques derived from…

Quantum Physics · Physics 2023-08-16 Kaito Mizukami , Akihisa Koga

The preparation of quantum Gibbs state is an essential part of quantum computation and has wide-ranging applications in various areas, including quantum simulation, quantum optimization, and quantum machine learning. In this paper, we…

Quantum Physics · Physics 2021-11-23 Youle Wang , Guangxi Li , Xin Wang

A quantum thermodynamic system is described by a Hamiltonian and a list of conserved, non-commuting charges, and a fundamental goal is to determine the minimum energy of the system subject to constraints on the charges. Recently, [Liu et…

Quantum simulation is one of the most promising scientific applications of quantum computers. Due to decoherence and noise in current devices, it is however challenging to perform digital quantum simulation in a regime that is intractable…

While recent advances have established efficient quantum algorithms for preparing Gibbs states of finite-dimensional systems, comparable complexity results for bosonic and other infinite-dimensional models remain unexplored. We introduce…

Quantum Physics · Physics 2026-04-08 Simon Becker , Cambyse Rouzé , Robert Salzmann

Thermalization (generalized thermalization) in nonintegrable (integrable) quantum systems requires two ingredients: equilibration and agreement with the predictions of the Gibbs (generalized Gibbs) ensemble. We prove that observables that…

Statistical Mechanics · Physics 2023-08-10 Patrycja Łydżba , Marcin Mierzejewski , Marcos Rigol , Lev Vidmar

While questions on quantum simulation of ground state physics are mostly focussed on the realization of effective interactions, most work on quantum simulation of thermal physics explores the realization of dynamics towards a thermal mixed…