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Nuclear quantum phenomena beyond the Born-Oppenheimer approximation are known to play an important role in a growing number of chemical and biological processes. While there exists no unique consensus on a rigorous and efficient…

We report an experimental realization of one-way quantum computing on a two-photon four-qubit cluster state. This is accomplished by developing a two-photon cluster state source entangled both in polarization and spatial modes. With this…

Quantum Physics · Physics 2012-10-30 Kai Chen , Che-Ming Li , Qiang Zhang , Yu-Ao Chen , Alexander Goebel , Shuai Chen , Alois Mair , Jian-Wei Pan

We present an efficient algorithm for twirling a multi-qudit quantum state. The algorithm can be used for approximating the twirling operation in an ensemble of physical systems in which the systems cannot be individually accessed. It can…

Quantum Physics · Physics 2007-05-23 Geza Toth , Juan Jose Garcia-Ripoll

Consider a bipartite quantum system with at least one of its two components being itself a composite system. By tracing over part of one (or both) of these two subsystems it is possible to obtain a reduced (separable) state that exhibits…

Quantum Physics · Physics 2015-04-10 Guido Bellomo , Ana P. Majtey , A. R. Plastino , A. Plastino

Quantum algorithms that can speed up certain tasks, such as factorisation and unstructured search, have driven a decades-long development of quantum computers and quantum technologies. Yet, outside specialized applications, quantum…

Quantum Physics · Physics 2019-07-05 Carlos Perez-Delgado , Sai Vinjanampathy

Quantum bits have technological imperfections. Additionally, the capacity of a component that can be implemented feasibly is limited. Therefore, distributed quantum computation is required to scale up quantum computers. This dissertation…

Quantum Physics · Physics 2017-04-11 Shota Nagayama

We demonstrate the use of the Variational Quantum Eigensolver (VQE) to simulate solid state crystalline materials. We adapt the Unitary Coupled Cluster ansatz to periodic boundary conditions in real space and momentum space representations…

In the past decade, coupled-cluster theory has seen a renaissance in nuclear physics, with computations of neutron-rich and medium-mass nuclei. The method is efficient for nuclei with product-state references, and it describes many aspects…

Nuclear Theory · Physics 2014-09-16 G. Hagen , T. Papenbrock , M. Hjorth-Jensen , D. J. Dean

We present a perturbative triples correction to the relativistic quadratic unitary coupled cluster singles and doubles (qUCCSD) method, denoted as qUCCSD[T]. The method builds upon the Hermitian structure of the unitary ansatz and employs a…

Chemical Physics · Physics 2025-10-08 Kamal Majee , Ján Šimunek , Jozef Noga , Achintya Kumar Dutta

We propose an approach to approximately implement the variational coupled cluster (VCC) theory on quantum computers, which struggles with exponential scaling of computational costs on classical computers. To this end, we employ expanding…

Quantum Physics · Physics 2024-06-12 Luca Erhart , Yuichiro Yoshida , Viktor Khinevich , Wataru Mizukami

We recently proposed a novel approach to converging electronic energies equivalent to high-level coupled-cluster (CC) computations by combining the deterministic CC($P$;$Q$) formalism with the stochastic configuration interaction (CI) and…

Chemical Physics · Physics 2021-03-23 J. Emiliano Deustua , Jun Shen , Piotr Piecuch

While the treatment of chemically relevant systems containing hundreds or even thousands of electrons remains beyond the reach of quantum devices, the development of quantum-classical hybrid algorithms to resolve electronic correlation…

Circuit depth reduction is of critical importance for quantum chemistry simulations on current and near term quantum computers. This issue is tackled by introducing a chemically aware strategy for the Unitary Coupled Cluster ansatz. The…

The aim of this work is to develop the relevant formalism for performing coupled-cluster (CC) calculations in nuclear matter and neutron star matter, including thereby important correlations to infinite order in the interaction and testing…

Nuclear Theory · Physics 2013-11-18 G. Baardsen , A. Ekström , G. Hagen , M. Hjorth-Jensen

An accurate description of strong correlation is quintessential for the exploration of emerging chemical phenomena. While near-term variational quantum algorithms provide a theoretically scalable framework for quantum chemical problems, the…

Quantum Physics · Physics 2025-10-20 Arpan Choudhury , Sonaldeep Halder , Rahul Maitra , Debashree Ghosh

Quantum computers hold immense potential in the field of chemistry, ushering new frontiers to solve complex many body problems that are beyond the reach of classical computers. However, noise in the current quantum hardware limits their…

Quantum Physics · Physics 2024-03-20 Chayan Patra , Sonaldeep Halder , Rahul Maitra

We introduce a novel many body method which combines two powerful many body techniques, viz., quantum Monte Carlo and coupled cluster theory. Coupled cluster wave functions are introduced as importance functions in a Monte Carlo method…

Nuclear Theory · Physics 2013-12-04 Alessandro Roggero , Abhishek Mukherjee , Francesco Pederiva

We present a quantum linear response (qLR) approach within an active-space framework for computing indirect nuclear spin-spin coupling constants, a key ingredient in NMR spectra predictions. The method employs the unitary coupled cluster…

Molecular simulations are widely regarded as leading candidates to demonstrate quantum advantage--defined as the point at which quantum methods surpass classical approaches in either accuracy or scale. Yet the qubit counts and error rates…

Considering recent advancements and successes in the development of efficient quantum algorithms for electronic structure calculations --- alongside impressive results using machine learning techniques for computation --- hybridizing…

Quantum Physics · Physics 2018-10-24 Rongxin Xia , Sabre Kais