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We study the level surfaces of quantum discord for a class of two-qubit states with parallel nonzero Bloch vectors. The dynamic behavior of quantum discord under decoherence is investigated. It is shown that a class of X states has sudden…

Quantum Physics · Physics 2011-04-12 Bo Li , Zhi-Xi Wang , Shao-Ming Fei

We investigate the boundary between classical and quantum computational power. This work consists of two parts. First we develop new classical simulation algorithms that are centered on sampling methods. Using these techniques we generate…

Quantum Physics · Physics 2012-02-20 M. Van den Nest

The usefulness of solid-state spins in quantum technologies depends on how long they can remain in a coherent superposition of quantum states. This Colloquium discusses how first-principles simulations can predict spin dynamics for…

Quantum Physics · Physics 2025-03-21 Mykyta Onizhuk , Giulia Galli

Consumption of magic states promotes the stabilizer model of computation to universal quantum computation. Here, we propose three different classical algorithms for simulating such universal quantum circuits, and characterize them by…

Quantum Physics · Physics 2021-03-23 James R. Seddon , Bartosz Regula , Hakop Pashayan , Yingkai Ouyang , Earl T. Campbell

Variational quantum circuits (VQCs) are a central component of many quantum machine learning algorithms, offering a hybrid quantum-classical framework that, under certain aspects, can be considered similar to classical deep neural networks.…

Quantum Physics · Physics 2025-07-16 Nicola Assolini , Luca Marzari , Isabella Mastroeni , Alessandra di Pierro

Optimization of circuits is an essential task for both quantum and classical computers to improve their efficiency. In contrast, classical logic optimization is known to be difficult, and a lot of heuristic approaches have been developed so…

Quantum Physics · Physics 2025-05-14 Yusei Mori , Hideaki Hakoshima , Kyohei Sudo , Toshio Mori , Kosuke Mitarai , Keisuke Fujii

We calculate steady-state properties of a strongly correlated quantum dot under voltage bias by means of non-equilibrium Cluster Perturbation Theory and the non-equilibrium Variational Cluster Approach, respectively. Results for the…

Strongly Correlated Electrons · Physics 2013-01-15 Martin Nuss , Christoph Heil , Martin Ganahl , Michael Knap , Hans Gerd Evertz , Enrico Arrigoni , Wolfgang von der Linden

Quantum discord as a measure of the quantum correlations cannot be easily computed for most of density operators. In this paper, we present a measure of the total quantum correlations that is operationally simple and can be computed…

Quantum Physics · Physics 2016-04-19 Javad Behdani , Seyed Javad Akhtarshenas , Mohsen Sarbishaei

Scaling quantum computers, i.e., quantum processing units (QPUs) to enable the execution of large quantum circuits is a major challenge, especially for applications that should provide a quantum advantage over classical algorithms. One…

Quantum Physics · Physics 2026-01-27 Leo Sünkel , Jonas Stein , Jonas Nüßlein , Tobias Rohe , Claudia Linnhoff-Popien

One-way quantum deficit and quantum discord are two important measures of quantum correlations. We revisit the relationship between them in two-qubit systems. We investigate the conditions that both one-way quantum deficit and quantum…

Quantum Physics · Physics 2016-01-12 Biao-Liang Ye , Shao-Ming Fei

We provide algorithms for efficiently addressing quantum memory in parallel. These imply that the standard circuit model can be simulated with low overhead by the more realistic model of a distributed quantum computer. As a result, the…

Quantum circuit compilation comprises many computationally hard reasoning tasks that nonetheless lie inside #$\mathbf{P}$ and its decision counterpart in $\mathbf{PP}$. The classical simulation of general quantum circuits is a core example.…

Quantum Physics · Physics 2024-03-13 Jingyi Mei , Marcello Bonsangue , Alfons Laarman

The ground state of a quantum spin chain is a natural playground for investigating correlations. Nevertheless, not all correlations are genuinely of quantum nature. Here we review the recent progress to quantify the 'quantumness' of the…

Quantum Physics · Physics 2015-03-20 Marcelo S. Sarandy , Thiago R. de Oliveira , Luigi Amico

Adaptive quantum circuits employ unitary gates assisted by mid-circuit measurement, classical computation on the measurement outcome, and the conditional application of future unitary gates based on the result of the classical computation.…

We investigate the disappearance of discord in 2- and multi-qubit systems subject to decohering influences. We formulate the computation of quantum discord in terms of the generalized Bloch vector, which gives useful insights on the time…

Quantum Physics · Physics 2014-04-21 Hyungjun Lim , Robert Joynt

Quantum computing systems need to be benchmarked in terms of practical tasks they would be expected to do. Here, we propose 3 "application-motivated" circuit classes for benchmarking: deep (relevant for state preparation in the variational…

Quantum Physics · Physics 2021-03-24 Daniel Mills , Seyon Sivarajah , Travis L. Scholten , Ross Duncan

This is a 1-page comment on a wrong paper that recently appeared in PRL (Phys. Rev. Lett. 86 (23), 5393 (2001), also quant-ph/0101004). The authors claim to have shown that using a quantum computer gives an "exponential advantage" for…

Quantum Physics · Physics 2007-05-23 Christof Zalka

Quantum computational advantage is a critical milestone for near-term quantum technologies and an essential step towards building practical quantum computers. Recent successful demonstrations of quantum computational advantage owe much to…

Quantum Physics · Physics 2025-01-28 He-Liang Huang , Youwei Zhao , Chu Guo

Motivated by improving the understanding of the quantum-to-classical transition we use a simple model of classical discrete interactions for studying the discrete-to-continuous transition in the classical harmonic oscillator. A parallel is…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Breno. R. Segatto , Julio S. Azevedo , Manoelito M. de Souza

In a pair of correlated quantum systems a measurement in one corresponds to a change in the state of the other. In the process, information is lost. Measurement along which set of projectors would accompany minimum loss in information…

Quantum Physics · Physics 2022-05-19 Chitradeep Gupta