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We propose a variational approach for preparing entangled quantum states on quantum computers. The methodology involves training a unitary operation to match with a target unitary using the Fubini-Study distance as a cost function. We…

Quantum Physics · Physics 2023-07-03 Vu Tuan Hai , Nguyen Tan Viet , Le Bin Ho

We present a self-consistent approach for computing the correlated quasiparticle spectrum of charged excitations in iterative $\mathcal{O}[N^5]$ computational time. This is based on the auxiliary second-order Green's function approach [O.…

Chemical Physics · Physics 2020-10-05 Oliver J. Backhouse , George H. Booth

Quantum computation of vibrational properties of molecules is a promising platform to obtain computational advantages for computational chemistry. However, fault-tolerant quantum computations of vibrational properties remain a relatively…

Can near-term gate model based quantum processors offer quantum advantage for practical applications in the pre-fault tolerance noise regime? A class of algorithms which have shown some promise in this regard are the so-called…

Quantum Physics · Physics 2019-08-13 Guillaume Verdon , Michael Broughton , Jacob Biamonte

Classical algorithms for predicting the equilibrium geometry of strongly correlated molecules require expensive wave function methods that become impractical already for few-atom systems. In this work, we introduce a variational quantum…

Unitary and non-unitary diagonal operators are fundamental building blocks in quantum algorithms with applications in the resolution of partial differential equations, Hamiltonian simulations, the loading of classical data on quantum…

Quantum Physics · Physics 2025-01-22 Julien Zylberman , Ugo Nzongani , Andrea Simonetto , Fabrice Debbasch

In this paper, we show how the two-particle Green function (2PGF) can be obtained within the framework of the Dual Fermion approach. This facilitates the calculation of the susceptibility in strongly correlated systems where long-ranged…

Strongly Correlated Electrons · Physics 2009-11-13 S. Brener , H. Hafermann , A. N. Rubtsov , M. I. Katsnelson , A. I. Lichtenstein

Non-Hermitian quantum systems, governed by nonunitary evolution, offer powerful tools for manipulating quantum states through engineered loss. A prime example is coherent absorption, where quantum states undergo phase-dependent partial or…

Non-equilibrium Green's function theory and related methods are widely used to describe transport phenomena in many-body systems, but they often require a costly inversion of a large matrix. We show here that the shift-invert Lanczos method…

Nuclear Theory · Physics 2025-01-14 K. Uzawa , K. Hagino

For the calculation of the partition function $\mathcal{Z}$ of small, isolated and interacting many body systems an improvement with respect to previous formulations is presented. By including anharmonicities and employing a variational…

Nuclear Theory · Physics 2009-11-10 Christian Rummel , Helmut Hofmann

A new approach proposed recently by author for the calculation of Green functions in quantum field theory and quantum mechanics is briefly reviewed. The method is applied to nonperturbative calculations for anharmonic oscillator,…

High Energy Physics - Theory · Physics 2007-05-23 V. E. Rochev

Hybrid quantum-classical algorithms have been proposed to circumvent noise limitations in quantum computers. Such algorithms delegate only a calculation of the expectation value to the quantum computer. Among them, the Variational Quantum…

Strongly Correlated Electrons · Physics 2022-11-02 Baptiste Anselme Martin , Pascal Simon , Marko J. Rančić

Variational hybrid quantum-classical algorithms are powerful tools to maximize the use of Noisy Intermediate Scale Quantum devices. While past studies have developed powerful and expressive ansatze, their near-term applications have been…

Quantum Physics · Physics 2021-06-30 Sukin Sim , Jonathan Romero , Jerome F. Gonthier , Alexander A. Kunitsa

We describe a quantum algorithm for preparing states that encode solutions of non-homogeneous linear partial differential equations. The algorithm is a continuous-variable version of matrix inversion: it efficiently inverts differential…

Quantum Physics · Physics 2019-09-11 Juan Miguel Arrazola , Timjan Kalajdzievski , Christian Weedbrook , Seth Lloyd

Variational quantum algorithms have been a promising candidate to utilize near-term quantum devices to solve real-world problems. The powerfulness of variational quantum algorithms is ultimately determined by the expressiveness of the…

Quantum Physics · Physics 2023-05-23 Xiaokai Hou , Qingyu Li , Man-Hong Yung , Xusheng Xu , Zizhu Wang , Chu Guo , Xiaoting Wang

Interacting spin systems in solids underpin a wide range of quantum technologies, from quantum sensors and single-photon sources to spin-defect-based quantum registers and processors. We develop a quantum-computer-aided framework for…

Quantum Physics · Physics 2026-01-30 Juan Naranjo , Thi Ha Kyaw , Gaurav Saxena , Kevin Ferreira , Jack S. Baker

The Quantum Singular Value Transformation (QSVT) is a technique that provides a unified framework for describing many of the quantum algorithms discovered to date. We implement a noise-free simulation of the technique to investigate how it…

Quantum Physics · Physics 2023-07-26 Alexis Ralli , Gabriel Greene-Diniz , David Muñoz Ramo , Nathan Fitzpatrick

We devise powerful algorithms based on differential evolution for adaptive many-particle quantum metrology. Our new approach delivers adaptive quantum metrology policies for feedback control that are orders-of-magnitude more efficient and…

Quantum Physics · Physics 2013-06-04 Neil B. Lovett , Cécile Crosnier , Martí Perarnau-Llobet , Barry C. Sanders

Several widely used methods for the calculation of band structures and photo emission spectra, such as the GW approximation, rely on Many-Body Perturbation Theory. They can be obtained by iterating a set of functional differential equations…

Strongly Correlated Electrons · Physics 2012-01-31 Giovanna Lani , Pina Romaniello , Lucia Reining

Digital quantum simulation (DQS) of continuous-variable quantum systems in the position basis requires efficient implementation of diagonal unitaries approximating the time evolution operator generated by the potential energy function. In…

Quantum Physics · Physics 2022-12-12 Tenzan Araki , James Stokes , Shravan Veerapaneni