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We explore the effectiveness of variational quantum circuits in simulating the ground states of quantum many-body Hamiltonians. We show that generic high-depth circuits, performing a sequence of layer unitaries of the same form, can…

Quantum Physics · Physics 2021-06-16 Joonho Kim , Jaedeok Kim , Dario Rosa

We explore the role of entanglement in adiabatic quantum optimization by performing approximate simulations of the real-time evolution of a quantum system while limiting the amount of entanglement. To classically simulate the time evolution…

Disordered Systems and Neural Networks · Physics 2015-01-29 Bela Bauer , Lei Wang , Iztok Pižorn , Matthias Troyer

We propose to detect quantum entanglement by a condition of local measurments. We find that this condition can detect efficiently the pure entangled states for both discrete and continuous variable systems. It does not depend on…

Quantum Physics · Physics 2015-05-30 Qing Xie , X. -X. Wu , X. -M. Ding , W. -L. Yang , R. -H. Yue , H. Fan

The performance of the Variational Quantum Eigensolver (VQE) is promising compared to other quantum algorithms, but also depends significantly on the appropriate design of the underlying quantum circuit. Recent research by Bowles, Ahmend \&…

It has recently been shown that finding the optimal measurement on the environment for stationary Linear Quadratic Gaussian control problems is a semi-definite program. We apply this technique to the control of the EPR-correlations between…

Quantum Physics · Physics 2009-11-13 Stefano Mancini , Howard M. Wiseman

We show that the general Heisenberg Hamiltonian with non-uniform couplings can be characterised by mapping the entanglement it generates as a function of time. Identification of the Hamiltonian in this way is possible as the coefficients of…

Quantum Physics · Physics 2007-05-23 Jared H. Cole , Simon J. Devitt , Lloyd C. L. Hollenberg

Entanglement is one of the most important concepts in quantum physics. We review recent progress in understanding the quantum entanglement in many-body systems using large-$N$ solvable models: the Sachdev-Ye-Kitaev (SYK) model and its…

Strongly Correlated Electrons · Physics 2022-03-04 Pengfei Zhang

In quantum information theory, the reliable and effective detection of entanglement is of paramount importance. However, given an unknown state, assessing its entanglement is a challenging task. To attack this problem, we investigate the…

Quantum Physics · Physics 2015-12-09 Jochen Szangolies , Hermann Kampermann , Dagmar Bruß

There has been a surge of progress in recent years in developing algorithms for testing and learning quantum states that achieve optimal copy complexity. Unfortunately, they require the use of entangled measurements across many copies of…

Quantum Physics · Physics 2020-04-20 Sebastien Bubeck , Sitan Chen , Jerry Li

The Variational Quantum Eigensolver (VQE) is a promising tool for simulating ground states of quantum many-body systems on noisy quantum computers. Its effectiveness relies heavily on the ansatz, which must be both hardware-efficient for…

Quantum Physics · Physics 2025-06-05 Alina Joch , Götz S. Uhrig , Benedikt Fauseweh

Variational quantum algorithms constitute one of the most widespread methods for using current noisy quantum computers. However, it is unknown if these heuristic algorithms provide any quantum-computational speedup, although we cannot…

The security analysis of quantum key distribution is difficult to perform when there is efficiency mismatch between various threshold detectors involved in an experimental setup. Even the verification that the device actually performs in…

Quantum Physics · Physics 2017-05-01 Yanbao Zhang , Norbert Lutkenhaus

Quantum entanglement is an indispensable resource for many significant quantum information processing tasks. However, because of the noise in quantum channels, it is difficult to distribute quantum entanglement over a long distance in…

Quantum Physics · Physics 2018-01-31 Zhaofeng Su , Ji Guan , Lvzhou Li

Quantum entanglement has been identified as a crucial concept underlying many intriguing phenomena in condensed matter systems, such as topological phases or many-body localization. Recently, instead of considering mere quantifiers of…

Quantum Physics · Physics 2024-02-12 Niklas Euler , Martin Gärttner

We introduce a general model for a network of quantum sensors, and we use this model to consider the question: When can entanglement between the sensors, and/or global measurements, enhance the precision with which the network can measure a…

Quantum Physics · Physics 2018-02-28 Timothy J. Proctor , Paul A. Knott , Jacob A. Dunningham

We explore a supervised machine learning approach to estimate the entanglement entropy of multi-qubit systems from few experimental samples. We put a particular focus on estimating both aleatoric and epistemic uncertainty of the network's…

Quantum Physics · Physics 2024-01-04 Maximilian Rieger , Moritz Reh , Martin Gärttner

It is a general fact that the coupling constant of an interacting many-body Hamiltonian do not correspond to any observable and one has to infer its value by an indirect measurement. For this purpose, quantum systems at criticality can be…

Quantum Physics · Physics 2009-11-13 Carmen Invernizzi , Michael Korbman , Lorenzo Campos Venuti , Matteo G. A Paris

Projective measurement, a basic operation in quantum mechanics, can induce seemingly nonlocal effects. In this work, we analyze such effects in many-body systems by studying the non-equilibrium dynamics of weakly monitored quantum circuits,…

Statistical Mechanics · Physics 2024-06-19 Shengqi Sang , Zhi Li , Timothy H. Hsieh , Beni Yoshida

We focus on using an architecture similar to the $\beta$-Variational Autoencoder ($\beta$-VAE) to discriminate if a quantum state is entangled or separable based on measurements. We split the data into two sets, the set of local and…

Quantum Physics · Physics 2021-10-19 Nahum Sá , Itzhak Roditi

Many classical optimization problems can be mapped to finding the ground states of diagonal Ising Hamiltonians, for which variational quantum algorithms such as the Quantum Approximate Optimization Algorithm (QAOA) provide heuristic…

Quantum Physics · Physics 2023-07-11 Yanzhu Chen , Linghua Zhu , Chenxu Liu , Nicholas J. Mayhall , Edwin Barnes , Sophia E. Economou