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Construction of quantum circuit for a generic linear combination of unitaries: Simulation of optical absorption spectra of molecules

Taichi Kosugi, Yu‐ichiro Matsushita

The Japan Society of Applied PhysicsJul 9, 20200 citations

Linear-response functions of molecules on a quantum computer: Charge and spin responses and optical absorption

Taichi Kosugi, Yu‐ichiro Matsushita

This work proposes a generic construction scheme for the quantum circuit implementing a nonunitary operator appearing in electronic-structure calculations. The authors demonstrate that the scheme enables one via probabilistic state preparation to calculate the linear-response functions of diatomic molecules, where simulated measurements and full configuration-interaction results are compared.

arXiv:1911.00293Physical Review ResearchJul 9, 202019 citations

Variational Quantum Computation of Molecular Linear Response Properties on a Superconducting Quantum Processor

Kaixuan Huang, Xiaoxia Cai, Hao Li +12 more

Simulating response properties of molecules is crucial for interpreting experimental spectroscopies and accelerating materials design. However, it remains a long-standing computational challenge for electronic structure methods on classical computers. While quantum computers hold the promise of solving this problem more efficiently in the long run, existing quantum algorithms requiring deep quantum circuits are infeasible for near-term noisy quantum processors. Herein, we introduce a pragmatic variational quantum response (VQR) algorithm for response properties, which circumvents the need for deep quantum circuits. Using this algorithm, we report the first simulation of linear response properties of molecules including dynamic polarizabilities and absorption spectra on a superconducting quantum processor. Our results indicate that a large class of important dynamical properties, such as Green's functions, are within the reach of near-term quantum hardware using this algorithm in combination with suitable error mitigation techniques.Simulating response properties of molecules is crucial for interpreting experimental spectroscopies and accelerating materials design. However, it remains a long-standing computational challenge for electronic structure methods on classical computers. While quantum computers hold the promise of solving this problem more efficiently in the long run, existing quantum algorithms requiring deep quantum circuits are infeasible for near-term noisy quantum processors. Herein, we introduce a pragmatic variational quantum response (VQR) algorithm for response properties, which circumvents the need for deep quantum circuits. Using this algorithm, we report the first simulation of linear response properties of molecules including dynamic polarizabilities and absorption spectra on a superconducting quantum processor. Our results indicate that a large class of important dynamical properties, such as Green's functions, are within the reach of near-term quantum hardware using this algorithm in combination with suitable error mitigation techniques.

arXiv:2201.02426The Journal of Physical Chemistry LettersSep 26, 202249 citations

Linear response function for quantum mechanical system

J. Ranninger, Walter E Thirring

The European Physical Journal AFeb 1, 19635 citations

Nonequilibrium quantum probing through linear response

S. Blair, Giorgio Zicari, Alessio Belenchia +2 more

The formalism of linear response theory can be extended to encompass physical situations where an open quantum system evolves toward a nonequilibrium steady state. Here, we use the framework put forward by Konopik and Lutz [] to go beyond unitary perturbations of the dynamics. Considering an open system comprised of two coupled quantum harmonic oscillators, we study the system's response to unitary perturbations, affecting the Hamiltonian dynamics, as well as nonunitary perturbations, affecting the properties of the environment, e.g., its temperature and squeezing. We show that linear response, combined with a quantum probing approach, can effectively provide valuable quantitative information about the perturbation and characteristics of the environment, even in cases of nonunitary dynamics. Published by the American Physical Society 2024The formalism of linear response theory can be extended to encompass physical situations where an open quantum system evolves toward a nonequilibrium steady state. Here, we use the framework put forward by Konopik and Lutz [] to go beyond unitary perturbations of the dynamics. Considering an open system comprised of two coupled quantum harmonic oscillators, we study the system's response to unitary perturbations, affecting the Hamiltonian dynamics, as well as nonunitary perturbations, affecting the properties of the environment, e.g., its temperature and squeezing. We show that linear response, combined with a quantum probing approach, can effectively provide valuable quantitative information about the perturbation and characteristics of the environment, even in cases of nonunitary dynamics. Published by the American Physical Society 2024

arXiv:2306.08500Physical Review ResearchFeb 9, 20245 citations

Synthesis of Quantum Circuits

Philipp Niemann, Robert Wille

SpringerBriefs in physicsJan 1, 20170 citations

Generic constructin of quantum circuits for nonunitary operations: linear-response functions of molecules

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