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Molecular quantum-dot Cellular Automata (QCA) may provide low-power, high-speed computational hardware for processing classical information. Simulation and modeling play an important role in the design of QCA circuits because fully-coherent…

Quantum Physics · Physics 2025-10-15 Nischal Binod Gautam , Enrique P. Blair

The variational quantum eigensolver (VQE) is currently the flagship algorithm for solving electronic structure problems on near-term quantum computers. This hybrid quantum/classical algorithm involves implementing a sequence of…

The variational quantum eigensolver (VQE) is a promising algorithm for demonstrating quantum advantage in the noisy intermediate-scale quantum (NISQ) era. However, optimizing VQE from random initial starting parameters is challenging due to…

Quantum Physics · Physics 2023-10-20 Abid Khan , Bryan K. Clark , Norm M. Tubman

Variational Quantum Eigensolver (VQE) is a hybrid algorithm for finding the minimum eigenvalue/vector of a given Hamiltonian by optimizing a parametrized quantum circuit (PQC) using a classical computer. Sequential optimization methods,…

Quantum Physics · Physics 2024-05-17 Katsuhiro Endo , Yuki Sato , Rudy Raymond , Kaito Wada , Naoki Yamamoto , Hiroshi C. Watanabe

We propose a quantum-classical hybrid algorithm to simulate the non-equilibrium steady state of an open quantum many-body system, named the dissipative-system Variational Quantum Eigensolver (dVQE). To employ the variational optimization…

Quantum Physics · Physics 2020-12-07 Nobuyuki Yoshioka , Yuya O. Nakagawa , Kosuke Mitarai , Keisuke Fujii

We present computational chemistry data for small molecules ($CO$, $HCl$, $F_2$, $NH_4^+$, $CH_4$, $NH_{3}$, $H_3O^+$, $H{_2}O$, $BeH_{2}$, $LiH$, $OH^-$, $HF$, $HeH^+$, $H_2$), obtained by implementing the Unitary Coupled Cluster method…

Quantum Physics · Physics 2019-07-02 V. Armaos , Dimitrios A. Badounas , Paraskevas Deligiannis

In this work, we combine the recently developed double unitary coupled cluster (DUCC) theory with the adaptive, problem-tailored variational quantum eigensolver (ADAPT-VQE) to explore accuracy of unitary downfolded Hamiltonians for quantum…

Variational Monte Carlo (VMC) methods are used to sample classically from distributions corresponding to quantum states which have an efficient classical description. VMC methods are based on performing a number of steps of a Markov chain…

Quantum Physics · Physics 2023-10-27 Ashley Montanaro , Stasja Stanisic

In order to answer the problem of Quantum Phase Estimation Algorithm been not suitable for NISQ devices, and allows one to outperform classical computers, Variational Quantum Algorithms (VQAs) were designed. Our subject of interest is the…

Quantum Physics · Physics 2022-10-28 Max Alteg , Baptiste Chevalier , Octave Mestoudjian , Johan-Luca Rossi

Quantum simulation, one of the most promising applications of a quantum computer, is currently being explored intensely using the variational quantum eigensolver. The feasibility and performance of this algorithm depend critically on the…

Anharmonic potential quantum system play crucial role in physics as they provide a more realistic description of oscillatory phenomena, which often deviate from the idealized harmonic model. However, simulating such system on classical…

Quantum Physics · Physics 2025-10-08 Saurav Suman , Bikash K. Behera , Vivek Vyas , Prasanta k. Panigrahi

We assess the performance of the Quantum Flow (QFlow) algorithm employing cost-effective solvers based on the unitary coupled-cluster ansatz with single and double excitations (QFlow-SD). The resulting energies are benchmarked against those…

Chemical Physics · Physics 2026-05-05 Bhumika Jayee , Nathan M. Myers , Duo Song , Eric J. Bylaska , Karol Kowalski , Nicholas P. Bauman

We develop an extension of the variational quantum eigensolver (VQE) algorithm - multistate, contracted VQE (MC-VQE) - that allows for the efficient computation of the transition energies between the ground state and several low-lying…

Quantum Physics · Physics 2019-06-19 Robert M. Parrish , Edward G. Hohenstein , Peter L. McMahon , Todd J. Martinez

The calculation time for the energy of atoms and molecules scales exponentially with system size on a classical computer but polynomially using quantum algorithms. We demonstrate that such algorithms can be applied to problems of chemical…

Quantum Physics · Physics 2007-05-23 Alán Aspuru-Guzik , Anthony D. Dutoi , Peter J. Love , Martin Head-Gordon

Ab initio electronic excited state calculations are necessary for the quantitative study of photochemical reactions, but their accurate computation on classical computers is plagued by prohibitive scaling. The Variational Quantum Deflation…

The VQE algorithm has turned out to be quite expensive to run given the way we currently access quantum processors (i.e. over the cloud). In order to alleviate this issue, we introduce Quantum Sampling Regression (QSR), an alternative…

Quantum Physics · Physics 2020-12-07 Pedro Rivero , Ian C. Cloët , Zack Sullivan

The iterative qubit coupled cluster (iQCC) method is a systematic variational approach to solve the electronic structure problem on universal quantum computers. It is able to use arbitrarily shallow quantum circuits at expense of iterative…

Quantum Physics · Physics 2020-09-30 Ilya G. Ryabinkin , Artur F. Izmaylov , Scott N. Genin

We use the Variational Quantum Eigensolver (VQE) as implemented in the Qiskit software package to compute the ground state energy of small molecules derived from water, H$_2$O, and hydrogen cyanide, HCN. The work aims to benchmark…

Quantum Physics · Physics 2021-07-07 P. Lolur , M. Rahm , M. Skogh , L. García-Álvarez , G. Wendin

We present a new optimization method for small-to-intermediate scale variational algorithms on noisy near-term quantum processors which uses a Gaussian process surrogate model equipped with a classically-evaluated quantum kernel.…

Quantum Physics · Physics 2023-08-16 Alistair W. R. Smith , A. J. Paige , M. S. Kim

Quantum chemistry is envisioned as an early and disruptive application for quantum computers. Yet, closer scrutiny of the proposed algorithms shows that there are considerable difficulties along the way. Here, we propose two criteria for…

Quantum Physics · Physics 2026-04-09 Thibaud Louvet , Thomas Ayral , Xavier Waintal