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We describe a method to obtain the reduced density matrix (RDM) correct up to second order in system-bath coupling in \emph{nonequilibrium} steady state situations. The RDM is obtained via a scheme based on analytic continuation, using the…

Statistical Mechanics · Physics 2013-11-22 Juzar Thingna , Jian-Sheng Wang , Peter Hänggi

Obtaining accurate representations of the eigenstates of an array of coupled superconducting qubits is a crucial step in the design of circuit quantum electrodynamics (QED)-based quantum processors. However, exact diagonalization of the…

The one-particle reduced density-matrix (1-RDM) functional theory is a promising alternative to density-functional theory (DFT) that uses the 1-RDM rather than the electronic density as a basic variable. However, long-standing challenges…

Quantum Physics · Physics 2024-08-20 Matthieu Vladaj , Quentin Marécat , Bruno Senjean , Matthieu Saubanère

Estimating properties of quantum states via randomized measurements has become a significant part of quantum information science. In this paper, we design an innovative approach leveraging metasurfaces to perform randomized measurements on…

Quantum Physics · Physics 2024-04-22 Hang Ren , Yipei Zhang , Ze Zheng , Cuifeng Ying , Lei Xu , Mohsen Rahmani , K. Birgitta Whaley

A standard approach to quantum computing is based on the idea of promoting a classically simulable and fault-tolerant set of operations to a universal set by the addition of `magic' quantum states. In this context, we develop a general…

Quantum Physics · Physics 2022-04-12 Matteo Lostaglio , Alessandro Ciani

The goal of qubit purification is to combine multiple noisy copies of an unknown pure quantum state to obtain one or more copies that are closer to the pure state. We show that a simple protocol based solely on random SWAP tests achieves…

Quantum Physics · Physics 2025-12-23 Shrigyan Brahmachari , Austin Hulse , Henry D. Pfister , Iman Marvian

Quantum metrology stands as a leading application of quantum science and technology, yet noise often constrains its precision and sensitivity. In near-term quantum metrology, existing protocols largely depend on virtual state purification,…

Quantum Physics · Physics 2025-12-03 Xiaodie Lin , Haidong Yuan

By harnessing the quantum states of light for illumination, precise phase and absorption estimations can be achieved with precision beyond the standard quantum limit. Despite their significance for precision measurements, quantum states are…

Quantum Physics · Physics 2018-08-15 Ming Li , Chang-Ling Zou , Di Liu , Guo-Ping Guo , Guang-Can Guo , Xi-Feng Ren

A major bottleneck in the quest for scalable many-body quantum technologies is the difficulty in benchmarking their preparations, which suffer from an exponential `curse of dimensionality' inherent to their quantum states. We present an…

Quantum Physics · Physics 2019-07-31 Juan Carrasquilla , Giacomo Torlai , Roger G. Melko , Leandro Aolita

Efficiently estimating fermionic Hamiltonian expectation values is vital for simulating various physical systems. Classical shadow (CS) algorithms offer a solution by reducing the number of quantum state copies needed, but noise in quantum…

Quantum Physics · Physics 2024-04-19 Bujiao Wu , Dax Enshan Koh

Quantum computing has emerged as a promising platform for simulating strongly correlated systems in chemistry, for which the standard quantum chemistry methods are either qualitatively inaccurate or too expensive. However, due to the…

Chemical Physics · Physics 2024-05-06 Max Rossmannek , Fabijan Pavošević , Angel Rubio , Ivano Tavernelli

This is a brief description of how to protect quantum states from dissipation and decoherence that arise due to uncontrolled interactions with the environment. We discuss recoherence and stabilisation of quantum states based on two…

Quantum Physics · Physics 2007-05-23 A. Ekert , C. Macchiavello

The direct variational optimization of the two-electron reduced density matrix (2RDM) can provide a reference-independent description of the electronic structure of many-electron systems that naturally captures strong or nondynamic…

Chemical Physics · Physics 2024-06-19 Run R. Li , Marcus D. Liebenthal , A. Eugene DePrince

The reduced-density-matrix method is an promising candidate for the next generation electronic structure calculation method; it is equivalent to solve the Schr\"odinger equation for the ground state. The number of variables is the same as a…

Strongly Correlated Electrons · Physics 2011-06-27 Maho Nakata , Mituhiro Fukuda , Katsuki Fujisawa

The numerical solution of the many-body problem of interacting electrons and ions is a key challenge in condensed matter physics, chemistry, and materials science. Traditional methods to solve the multi-component quantum Hamiltonian are…

Materials Science · Physics 2025-10-24 Lorenzo Monacelli , Antonio Siciliano , Nicola Marzari

We present a novel strategy for obtaining optimal probe states and measurement schemes in a class of noiseless multiparameter estimation problems with symmetry among the generators. The key to the framework is the introduction of a set of…

Quantum Physics · Physics 2024-09-26 Sivaprasad Omanakuttan , Jonathan A. Gross , T. J. Volkoff

Characterizing the environmental interactions of quantum systems is a critical bottleneck in the development of robust quantum technologies. Traditional tomographic methods are often data-intensive and struggle with scalability. In this…

Quantum Physics · Physics 2025-09-16 Antonin Sulc

Hyperentanglement is a promising resource in quantum information processing, especially for increasing the channel capacity of long-distance quantum communication. Hyperentanglement purification is an important method to obtain…

Quantum Physics · Physics 2015-06-22 Bao-Cang Ren , Fang-Fang Du , Fu-Guo Deng

Simulating strongly correlated fermionic systems is notoriously hard on classical computers. An alternative approach, as proposed by Feynman, is to use a quantum computer. Here, we discuss quantum simulation of strongly correlated fermionic…

Quantum Physics · Physics 2018-05-02 Zhang Jiang , Kevin J. Sung , Kostyantyn Kechedzhi , Vadim N. Smelyanskiy , Sergio Boixo

For many-electron systems, the second-order reduced density matrix (2-RDM) provides sufficient information for characterizing their properties of interests in physics and chemistry, ranging from total energy, magnetism, quantum correlation…

Quantum Physics · Physics 2021-05-12 Yimin Li
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