慶應義塾研究者情報データベース

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• Synthesis and characterization of a formal 21-electron cobaltocene derivative

  Takebayashi S., Ariai J., Gellrich U., Kartashov S.V., Fayzullin R.R., Kang H.B., Yamane T., Sugisaki K., Sato K.

  Nature Communications （Nature Communications）  14 （ 1 ）  2023年12月

  　概要を見る

  Metallocenes are highly versatile organometallic compounds. The versatility of the metallocenes stems from their ability to stabilize a wide range of formal electron counts. To date, d-block metallocenes with an electron count of up to 20 have been synthesized and utilized in catalysis, sensing, and other fields. However, d-block metallocenes with more than formal 20-electron counts have remained elusive. The synthesis and isolation of such complexes are challenging because the metal–carbon bonds in d-block metallocenes become weaker with increasing deviation from the stable 18-electron configuration. Here, we report the synthesis, isolation, and characterization of a 21-electron cobaltocene derivative. This discovery is based on the ligand design that allows the coordination of an electron pair donor to a 19-electron cobaltocene derivative while maintaining the cobalt–carbon bonds, a previously unexplored synthetic approach. Furthermore, we elucidate the origin of the stability, redox chemistry, and spin state of the 21-electron complex. This study reveals a synthetic method, structure, chemical bonding, and properties of the 21-electron metallocene derivative that expands our conceptual understanding of d-block metallocene chemistry. We expect that this report will open up previously unexplored synthetic possibilities in d-block transition metal chemistry, including the fields of catalysis and materials chemistry.

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• Projective Measurement-Based Quantum Phase Difference Estimation Algorithm for the Direct Computation of Eigenenergy Differences on a Quantum Computer

  Sugisaki K.

  Journal of chemical theory and computation （Journal of chemical theory and computation）  19 （ 21 ） 7617 - 7625 2023年11月

  　概要を見る

  Quantum computers are capable of calculating the energy difference of two electronic states using the quantum phase difference estimation (QPDE) algorithm. The Bayesian inference-based implementations for the QPDE have been reported so far, but in this approach, the quality of the calculated energy difference depends on the input wave functions being used. Here, we report the inverse quantum Fourier transformation-based QPDE with Na of ancillary qubits, which allows us to compute the difference of eigenenergies based on the single-shot projective measurement. As proof-of-concept demonstrations, we report numerical experiments for the singlet-triplet energy difference of the hydrogen molecule and the vertical excitation energies of halogen-substituted methylenes (CHF, CHCl, CF2, CFCl, and CCl2) and formaldehyde (HCHO).

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• Adapting the Harrow-Hassidim-Lloyd algorithm to quantum many-body theory

  Baskaran N., Rawat A.S., Jayashankar A., Chakravarti D., Sugisaki K., Roy S., Mandal S.B., Mukherjee D., Prasannaa V.S.

  Physical Review Research （Physical Review Research）  5 （ 4 ）  2023年10月

  ISSN  26431564

  　概要を見る

  Rapid progress in developing near- and long-term quantum algorithms for quantum chemistry has provided us with an impetus to move beyond traditional approaches and explore new ways to apply quantum computing to electronic structure calculations. In this work, we identify the connection between quantum many-body theory and a quantum linear solver, and implement the Harrow-Hassidim-Lloyd (HHL) algorithm to make precise predictions of correlation energies for light molecular systems via the (nonunitary) linearized coupled cluster theory, where the term "light molecular systems"refers to those molecules whose constituent atoms have low atomic number. For the purposes of practical computations, we make suitable changes to the HHL framework. This entails two aspects: (1) Adapt, prescribing a novel scaling approach that allows one to scale any arbitrary Hermitian matrix, A, that in turn dictates the controlled-rotation angles without having to precompute the eigenvalues of A, and yet achieve a reasonably high precision in |x), and (2) Lite, for which we devise techniques that reduce the depth of the relevant quantum circuit. In this context, we introduce the following variants of HHL for different eras of quantum computing: AdaptHHLite in its appropriate forms for noisy intermediate-scale quantum (NISQ), late-NISQ, and the early fault-tolerant eras, as well as AdaptHHL for the fault-tolerant quantum computing era. We demonstrate the ability of the NISQ variant of AdaptHHLite to capture correlation energy precisely, while simultaneously being resource lean, using simulation as well as the 11-qubit IonQ quantum hardware.

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• Bayesian phase difference estimation algorithm for direct calculation of fine structure splitting: accelerated simulation of relativistic and quantum many-body effects

  Sugisaki K., Prasannaa V.S., Ohshima S., Katagiri T., Mochizuki Y., Sahoo B.K., Das B.P.

  Electronic Structure （Electronic Structure）  5 （ 3 ）  2023年09月

  　概要を見る

  Despite rapid progress in the development of quantum algorithms in quantum computing as well as numerical simulation methods in classical computing for atomic and molecular applications, no systematic and comprehensive electronic structure study of atomic systems that covers almost all of the elements in the periodic table using a single quantum algorithm has been reported. In this work, we address this gap by implementing the recently-proposed quantum algorithm, the Bayesian phase difference estimation (BPDE) approach, to determine fine structure splittings of a wide range of boron-like atomic systems. Since accurate estimate of fine structure splittings strongly depend on the relativistic as well as quantum many-body effects, our study can test the potential of the BPDE approach to produce results close to the experimental values. Our numerical simulations reveal that the BPDE algorithm, in the Dirac-Coulomb-Breit framework, can predict fine structure splittings of ground states of the considered systems quite precisely. We performed our simulations of relativistic and electron correlation effects on Graphics Processing Unit by utilizing NVIDIA’s cuQuantum, and observe a ×42.7 speedup as compared to the Central Processing Unit-only simulations in an 18-qubit active space.

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• Slow Magnetic Relaxation of Ni(III) Complexes toward Molecular Spin Qubits

  Toshima K., Sato T., Horii Y., Sato K., Sugisaki K., Breedlove B.K., Takaishi S., Li Z.Y., Yamashita M.

  European Journal of Inorganic Chemistry （European Journal of Inorganic Chemistry）  26 （ 19 ）  2023年07月

  ISSN  14341948

  　概要を見る

  Molecule-based magnetic materials are promising candidates for molecular spin qubits, which utilize spin relaxation behavior. Various kinds of transition metal complexes with S=1/2 have been reported to act as spin qubits with long spin-spin relaxation times (T2). However, the spin qubit properties of low-spin Ni(III) complexes are not as well known since Ni(III) compounds are often unstable. We report here the slow magnetic relaxation behavior and T2 values for three kinds of low-spin Ni(III) based complexes with S=1/2 under magnetically diluted conditions. [Ni(cyclam)X2]Y (cyclam=1,4,8,11-tetraazacyclotetradecane) with octahedral structures and [Ni(mnt)2]− (mnt=maleonitriledithiolate) with a square-planar structure underwent slow magnetic relaxations in the presence of a dc magnetic bias field. From electron spin resonance (ESR) spectroscopy, the Ni(III) complexes exhibited observable T2, indicating that Ni(III) complexes are promising candidates for use as molecule-based spin qubits.

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競争的研究費の研究課題 【 表示 ／ 非表示 】

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• スピン対称性を活用した量子化学計算量子アルゴリズムの開発

  2021年04月

  -

  2024年03月

  杉崎 研司, 基盤研究(C), 補助金,  研究代表者