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Solving for molecular excited states remains one of the key challenges of modern quantum chemistry. Traditional methods are constrained by existing computational capabilities, limiting the complexity of the molecules that can be studied or…

Quantum Physics · Physics 2021-04-13 Jules Tilly , Glenn Jones , Hongxiang Chen , Leonard Wossnig , Edward Grant

Electronic excited states are central to a vast array of physical and chemical phenomena, yet accurate and efficient methods for preparing them on quantum devices remain challenging and comparatively underexplored. We introduce a general…

Quantum Physics · Physics 2026-02-02 Hao-En Li , Lin Lin

Determining quantum excited states is crucial across physics and chemistry but presents significant challenges for variational methods, primarily due to the need to enforce orthogonality to lower-energy states, often requiring…

Quantum Physics · Physics 2025-05-01 Shi-Xin Zhang , Lei Wang

The Variational Quantum Eigensolver (VQE), as a hybrid quantum-classical algorithm, is an important tool for effective quantum computing in the current noisy intermediate-scale quantum (NISQ) era. However, the traditional hardware-efficient…

Strongly Correlated Electrons · Physics 2025-11-20 Shaohui Yao , Wenyu Wang

Many quantum algorithms rely on a quality initial state for optimal performance. Preparing an initial state for specific applications can considerably reduce the cost of probabilistic algorithms such as the well studied quantum phase…

Quantum Physics · Physics 2024-12-10 Alexandre Fleury , James Brown , Erika Lloyd , Maritza Hernandez , Isaac H. Kim

A method is presented in which the ground-state subspace is projected out of a Hamiltonian representation. As a result of this projection, an effective Hamiltonian is constructed where its ground-state coincides with an excited-state of the…

Quantum Physics · Physics 2023-08-14 P. Jouzdani , S. Bringuier , M. Kostuk

We present a hardware-efficient optimization scheme for quantum chemistry calculations, utilizing the Sampled Quantum Diagonalization (SQD) method. Our algorithm, optimized SQD (SQDOpt), combines the classical Davidson method technique with…

Quantum Physics · Physics 2025-03-05 Nora Bauer , Kübra Yeter-Aydeniz , George Siopsis

The possibility of using quantum computers for electronic structure calculations has opened up a promising avenue for computational chemistry. Towards this direction, numerous algorithmic advances have been made in the last five years. The…

The variational quantum eigensolver is one of the most promising approaches for performing chemistry simulations using noisy intermediate-scale quantum (NISQ) processors. The efficiency of this algorithm depends crucially on the ability to…

Various methods have been developed for the quantum computation of the ground and excited states of physical and chemical systems, but many of them require either large numbers of ancilla qubits or high-dimensional optimization. The quantum…

Quantum Physics · Physics 2019-12-16 Kübra Yeter-Aydeniz , Raphael C. Pooser , George Siopsis

Easy and effective usage of computational resources is crucial for scientific calculations. Following our recent work of machine-learning (ML) assisted scheduling optimization [Ref: J. Comput. Chem. 2023, 44, 1174], we further propose 1)…

Chemical Physics · Physics 2024-08-05 Kai Yuan , Shuai Zhou , Ning Li , Tianyan Li , Bowen Ding , Danhuai Guo , Yingjin Ma

Downfolding coupled cluster (CC) techniques are powerful tools for reducing the dimensionality of many-body quantum problems. This work investigates how ground-state downfolding formalisms can target excited states using non-Aufbau…

Chemical Physics · Physics 2023-10-24 Nicholas P. Bauman

The possibility of performing quantum chemical calculations using quantum computers has attracted much interest. In this regard, variational quantum deflation (VQD) is a quantum-classical hybrid algorithm for the calculation of excited…

Chemical Physics · Physics 2022-06-06 Soichi Shirai , Takahiro Horiba , Hirotoshi Hirai

Quantum state preparation is an important subroutine in many quantum algorithms. The goal is to encode classical information directly to the quantum state so that it is possible to leverage quantum algorithms for data processing. However,…

Quantum Physics · Physics 2026-05-01 Oskari Kerppo , William Steadman , Ossi Niemimäki , Valtteri Lahtinen

Electronic excited states of molecules are central to many physical and chemical processes, and yet they are typically more difficult to compute than ground states. In this paper we leverage the advantages of quantum computers to develop an…

Quantum Physics · Physics 2023-05-09 Yuchen Wang , David A. Mazziotti

We present calculations of the ground and excited state energies of spin defects in solids carried out on a quantum computer, using a hybrid classical/quantum protocol. We focus on the negatively charged nitrogen vacancy center in diamond…

Quantum Physics · Physics 2025-07-01 Benchen Huang , Marco Govoni , Giulia Galli

We present a quantum information-inspired ansatz for the variational quantum eigensolver (VQE) and demonstrate its efficacy in calculating ground-state energies of atomic systems. Instead of adopting a heuristic approach, we start with an…

Quantum Physics · Physics 2025-08-19 Abdul Kalam , Prasenjit Deb , Akitada Sakurai , B. K. Sahoo , V. S. Prasannaa , B. P. Das

Quantum computing allows for the manipulation of highly correlated states whose properties quickly go beyond the capacity of any classical method to calculate. Thus one natural problem which could lend itself to quantum advantage is the…

Quantum Physics · Physics 2024-12-19 Kevin Lively , Tim Bode , Jochen Szangolies , Jian-Xin Zhu , Benedikt Fauseweh

The ADAPT-VQE algorithm is a promising method for generating a compact ansatz based on derivatives of the underlying cost function, and it yields accurate predictions of electronic energies for molecules. In this work we report the…

We present a novel method for improving the quantum simulation of the ground state energy of molecules. We perform a pre-processing step classically, which reduces the dimensionality of the problem by generating a custom mapping which…

Quantum Physics · Physics 2023-03-03 Kaur Kristjuhan , Mark Nicholas Jones