184 citations · 934 across the 51 of their papers we have counts for
52 papers
First-quantized quantum simulation with non-local potentials by matrix-product-state encoding
Kazuki Tsuoka, Taichi Kosugi, Masari Watanabe +2
Quantum simulations based on first-quantized approaches can offer lower space and gate complexities than second-quantized approaches. The gate requirements for these simulations ca…
End-to-End Molecular Dynamics with a Langevin Thermostat on Quantum Circuits
Masari Watanabe, Hirofumi Nishi, Taichi Kosugi +3
We construct a quantum-circuit framework for finite-temperature molecular dynamics in the canonical ensemble (NVT) with a Langevin thermostat, connecting canonical state preparatio…
Koopman--von Neumann Molecular Dynamics for Green--Kubo Transport Coefficients
Masari Watanabe, Hirofumi Nishi, Taichi Kosugi +3
We formulate the Green--Kubo transport coefficients of classical molecular dynamics as a readout problem for quantum algorithms using the Koopman--von Neumann (KvN) representation.…
Overcoming the Matrix-Product-State Encoding Barrier via DMRG-Guided Probabilistic Imaginary-Time Evolution
Masari Watanabe, Hirofumi Nishi, Taichi Kosugi +2
Ground-state preparation is a fundamental task in quantum simulation, because the overlap of the prepared state with the true ground state significantly affects the overall cost of…
Quantum algorithms for density functional theory with minimal readout
Yuansheng Zhao, Hirofumi Nishi, Taichi Kosugi +5
While quantum computers have shown significant promise for electronic structure calculations, their potential to accelerate density functional theory (DFT) calculations remains unc…
Channel-agnostic finite-temperature phase estimation averaged over variable grids: reconstruction of Green's function for dynamical mean-field theory
Taichi Kosugi, Hirofumi Nishi, Keito Kasebayashi +2
For treating correlated electronic systems on quantum computers, we propose a quantum-classical hybrid scheme for dynamical mean-field theory (DMFT). In the quantum part of the sch…
Error-corrected phase estimation averaged over variable grids on a trapped-ion quantum computer: hyperacuity spectra of a CO molecule adsorbed onto -FeC
Taichi Kosugi, Hirofumi Nishi, Keito Kasebayashi +2
Quantum phase estimation (QPE) is an underlying technology for extracting the excitation spectra of many-electron systems, yet its practical use on current hardware is hindered by…
Accelerated spin-adapted ground state preparation with non-variational quantum algorithms
Takumi Kobori, Taichi Kosugi, Hirofumi Nishi +2
Various methods have been explored to prepare the spin-adapted ground state, the lowest energy state within the Hilbert space constrained by externally specified values of the tota…
Quantum State Readout via Overlap-Based Feature Extraction
Hirofumi Nishi, Taichi Kosugi, Xinchi Huang +3
In this study, a method for quantum state readout and feature extraction is developed using quantum-overlap-based fitting of function expansions. The approach involves the quantum…
Demonstration of logical quantum phase estimation for X-ray absorption spectra
Hirofumi Nishi, Taichi Kosugi, Satoshi Hirose +2
In this study, we employed Fourier-based quantum phase estimation (QPE) to calculate X-ray absorption spectroscopy (XAS) spectra. The primary focus of this study is the calculation…
Tensor decomposition technique for qubit encoding of maximal-fidelity Lorentzian orbitals in real-space quantum chemistry
Taichi Kosugi, Xinchi Huang, Hirofumi Nishi +1
To simulate the real- and imaginary-time evolution of a many-electron system on a quantum computer based on the first-quantized formalism, we need to encode molecular orbitals (MOs…
A probabilistic imaginary-time evolution quantum algorithm for advection-diffusion equation: Explicit gate-level implementation and comparisons to quantum linear system algorithms
Xinchi Huang, Hirofumi Nishi, Taichi Kosugi +2
Simulating differential equations on classical computers becomes an intractable problem if the grid size is extremely large. Quantum computers are believed to achieve a possibly ex…
Machine learning supported annealing for prediction of grand canonical crystal structures
Yannick Couzinie, Yuya Seki, Yusuke Nishiya +4
This study investigates the application of Factorization Machines with Quantum Annealing (FMQA) to address the crystal structure problem (CSP) in materials science. FMQA is a black…
Approximate real-time evolution operator for potential with one ancillary qubit and application to first-quantized Hamiltonian simulation
Xinchi Huang, Taichi Kosugi, Hirofumi Nishi +1
In this article, we compare the methods implementing the real-time evolution operator generated by a unitary diagonal matrix where its entries obey a known underlying real function…
Orbital-free density functional theory with first-quantized quantum subroutines
Yusuke Nishiya, Hirofumi Nishi, Taichi Kosugi +1
In this study, we propose a quantum-classical hybrid scheme for performing orbital-free density functional theory (OFDFT) using probabilistic imaginary-time evolution (PITE), desig…
Encoded probabilistic imaginary-time evolution on a trapped-ion quantum computer for ground and excited states of spin qubits
Hirofumi Nishi, Yuki Takei, Taichi Kosugi +4
In this study, we employed a quantum computer to solve a low-energy effective Hamiltonian for spin defects in diamond (so-called NV centre) and wurtzite-type aluminium nitride, whi…
Qubit encoding for a mixture of localized functions
Taichi Kosugi, Shunsuke Daimon, Hirofumi Nishi +2
One of the crucial generic techniques for quantum computation is amplitude encoding. Although several approaches have been proposed, each of them often requires exponential classic…
Optimized synthesis of circuits for diagonal unitary matrices with reflection symmetry
Xinchi Huang, Taichi Kosugi, Hirofumi Nishi +1
During the noisy intermediate-scale quantum (NISQ) era, it is important to optimize the quantum circuits in circuit depth and gate count, especially entanglement gates, including t…
First-quantized adiabatic time evolution for the ground state of a many-electron system and the optimal nuclear configuration
Yusuke Nishiya, Hirofumi Nishi, Yannick Couzinié +2
We propose a novel adiabatic time evolution (ATE) method for obtaining the ground state of a quantum many-electron system on a quantum circuit based on first quantization. As a str…
Quadratic acceleration of multi-step probabilistic algorithms for state preparation
Hirofumi Nishi, Taichi Kosugi, Yusuke Nishiya +1
For quantum state preparation, a non-unitary operator is typically designed to decay undesirable states contained in an initial state using ancilla qubits and a probabilistic actio…
Annealing for prediction of grand canonical crystal structures: Efficient implementation of n-body atomic interactions
Yannick Couzinie, Yusuke Nishiya, Hirofumi Nishi +3
We propose an annealing scheme usable on modern Ising machines for crystal structures prediction (CSP) by taking into account the general n-body atomic interactions, and in particu…
Optimal scheduling in probabilistic imaginary-time evolution on a quantum computer
Hirofumi Nishi, Koki Hamada, Yusuke Nishiya +2
Ground-state preparation is an important task in quantum computation. The probabilistic imaginary-time evolution (PITE) method is a promising candidate for preparing the ground sta…
Acceleration of probabilistic imaginary-time evolution method combined with quantum amplitude amplification
Hirofumi Nishi, Taichi Kosugi, Yusuke Nishiya +1
A probabilistic imaginary-time evolution (PITE) method was proposed as a nonvariational method to obtain a ground state on a quantum computer. In this formalism, the success probab…
First-quantized eigensolver for ground and excited states of electrons under a uniform magnetic field
Taichi Kosugi, Hirofumi Nishi, Yu-ichiro Matsushita
First-quantized eigensolver (FQE) is a recently proposed framework of quantum computation for obtaining the ground state of an interacting electronic system based on probabilistic…