Decoherence of intramolecular vibrational entanglement in polyatomic molecules

Mishima, Kenji; Yamashita, Koichi

doi:10.1002/qua.21984

Cited by 7 publications

(13 citation statements)

References 49 publications

(37 reference statements)

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“…The locus of this line is shown on Fig. 3 and roughly 35 correlates with the onset of entanglement in the wavefunctions at the transition state. At lower energies than the transition state of non-Jahn-Teller systems, the effect of the spike is rapidly diminished and so the entanglement falls off.…”

Section: Results a Entanglement In The Ground-vibronic State First-mentioning

confidence: 99%

“…1 The entanglement between two subsystems is zero if their dynamics are independent of one another. The 35 entanglement is large in states that contain non-classical correlations, such as those seen in experiments in which Bell's inequalities are violated. In chemical applications, entanglement has been studied considering e.g., electron-vibration, [2][3][4][5][6][7][8][9][10][11][12][13][14][15] electronelectron, [16][17][18][19][20][21][22][23][24][25][26][27][28][29] vibration-vibration, [30][31][32][33][34][35][36][37][38][39][40][41] vibration-rotation, 42, 43 40 rotation-rotation, 44 and electron-spin [45][46][47][48][49] interactions.…”

Section: Introductionmentioning

confidence: 99%

“…While unitary transformations of basis sets do not modify entanglement, 1 Eqn. (7) is non-unitary owing to its parametric dependence on the 35 nuclear coordinate. Hence the entanglement measured in the diabatic basis CA will be different to that measured in the BO basis using FC, whereas other properties such as energies and dipole moments are independent of the choice of the electronic basis.…”

Section: D) Full and Approximate Quantum Solutions To The Model Usingmentioning

confidence: 99%

“…All matrix elements are evaluated analytically. 59 Calculations are mostly 35 rapidly convergent and we use a typically grossly excessive value of N = 256 functions.…”

Section: C) Full-quantum Solution To the Model Using Diabatic Electromentioning

confidence: 99%

“…We use this entanglement as a quantitative measure of the effects of BO breakdown. 35 Instead of using the BO description to understand the dissociation of the NaCl molecule, an alternative approach is to use diabatic wavefunctions, wavefunctions that are either purely ionic or purely radical with unchanging character as the molecule stretches. These diabatic wavefunctions are mixed in different 40 proportions at each nuclear geometry to make the BO adiabatic wavefunctions.…”

Section: Introductionmentioning

confidence: 99%

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Electron–vibration entanglement in the Born–Oppenheimer description of chemical reactions and spectroscopy

McKemmish

McKenzie

Hush

et al. 2015

Phys. Chem. Chem. Phys.

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Entanglement is sometimes regarded as the quintessential measure of the quantum nature of a system and its significance for the understanding of coupled electronic and vibrational motions in molecules has been conjectured. Previously, we considered the entanglement developed in a spatially localized diabatic basis representation of the electronic states, considering design rules for qubits in a low-temperature chemical quantum computer. We extend this to consider the entanglement developed during high-energy processes. We also consider the entanglement developed using adiabatic electronic basis, providing a novel way for interpreting effects of the breakdown of the Born-Oppenheimer (BO) approximation. We consider: (i) BO entanglement in the ground-state wavefunction relevant to equilibrium thermodynamics, (ii) BO entanglement associated with low-energy wavefunctions relevant to infrared and tunneling spectroscopies, (iii) BO entanglement in high-energy eigenfunctions relevant to chemical reaction processes, and (iv) BO entanglement developed during reactive wavepacket dynamics. A two-state single-mode diabatic model descriptive of a wide range of chemical phenomena is used for this purpose. The entanglement developed by BO breakdown correlates simply with the diameter of the cusp introduced by the BO approximation, and a hierarchy appears between the various BO-breakdown correction terms, with the first-derivative correction being more important than the second-derivative correction which is more important than the diagonal correction. This simplicity is in contrast to the complexity of BO-breakdown effects on thermodynamic, spectroscopic, and kinetic properties. Further, processes poorly treated at the BO level that appear adequately treated using the Born-Huang adiabatic approximation are found to have properties that can only be described using a non-adiabatic description. For the entanglement developed between diabatic electronic states and the nuclear motion, qualitatively differently behavior is found compared to traditional properties of the density matrix and hence entanglement provides new information about system properties. For chemical reactions, this type of entanglement simply builds up as the transition-state region is crossed. It is robust to small changes in parameter values and is therefore more attractive for making quantum qubits than is the related fragile ground-state entanglement, provided that coherent motion at the transition state can be sustained.

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Section: Results a Entanglement In The Ground-vibronic State First-mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: D) Full and Approximate Quantum Solutions To The Model Usingmentioning

confidence: 99%

“…All matrix elements are evaluated analytically. 59 Calculations are mostly 35 rapidly convergent and we use a typically grossly excessive value of N = 256 functions.…”

Section: C) Full-quantum Solution To the Model Using Diabatic Electromentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Electron–vibration entanglement in the Born–Oppenheimer description of chemical reactions and spectroscopy

McKemmish

McKenzie

Hush

et al. 2015

Phys. Chem. Chem. Phys.

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Best molecular multiple quantum bit for the diatomic molecular quantum computer using potassium nitride and calcium nitride through vibrational progression

Ishii

2014

Int. J. Quantum Chem.

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In this article, based on the former accurate and precise ab initio calculation results for potassium nitride (KN) and calcium nitride (CaN), I revisit the possibilities and potentials of KN and CaN as the best candidate for molecular multiple quantum bit (MMQB) for the diatomic molecular quantum computer (DMQC), and would like to propose the two molecules as CPUs of the DMQC. Lowest lying four electronic states of CaN are energetically located within 1800 cm−1. These four states form the good molecular electronic two quantum bits through the dipole and weak spin–orbit interactions. 3Π state of KN is calculated to lie above ground 3Σ− state by 177 cm−1. KN is a promising candidate for an electronic one quantum bit. When vibrational progression is considered to be accompanied by the electronic transition, CaN and KN are good candidates for larger MMQBs up to a thousand even in the single molecule because the concrete quantum state bearing the quantum bit is each molecular ro‐vibronic state, that is, the specific rotational state on each vibronic level. When CaN and KN work in assemblies as quantum bit, those assemblies become larger MMQBs, the number of which might reach the Avogadro number because the molecular spectra appearing in the molecular spectroscopy are the results from the observation by the photon‐exchange among intramolecular quantum states made up of 1015 to the Avogadro (6.02 × 1023 mol−1) number of molecules interacting with radiation. Even without the vibrational progression, in the case of the lowest two quantum bit of KN, which is a stable vibronic two quantum bit, a thousand of KN molecules provide a thousand of MMQBs. That is the same situation as that for CaN. Using KN and CaN as MMQBs (playing the triple roles of CPU, RAMs (memory), and storages) ultra‐fast “in core” quantum computation can be done. An application of the full‐CI quantum chemistry calculation results for the demonstration of the DMQC is discussed. I strongly hope that the MMQB will “oscillate” and that the DMQC will be realized in the near future for the welfare of human being and the further development of modern material civilization. © 2014 Wiley Periodicals, Inc.

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Dynamical entanglement of stretching–stretching and stretching–bending vibrations in SO₂

Zhai

Zheng

2014

Int J of Quantum Chemistry

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The dynamics of stretching–stretching (SS) and stretching–bending (SB) entanglement in the normal mode molecule SO2 are studied by the Lie algebraic method. The influence of the decoherence from the remaining vibrational mode is considered. We have found that SS vibrations can achieve a higher degree of entanglement than the SB vibrations, and the degeneration rate of SB entanglement is higher than the SS entanglement. By the comparative study, the SS vibrations are found to be more suitable to construct a biqubit system rather than the stretching–bending vibrations. © 2014 Wiley Periodicals, Inc.

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Decoherence of intramolecular vibrational entanglement in polyatomic molecules

Cited by 7 publications

References 49 publications

Electron–vibration entanglement in the Born–Oppenheimer description of chemical reactions and spectroscopy

Electron–vibration entanglement in the Born–Oppenheimer description of chemical reactions and spectroscopy

Best molecular multiple quantum bit for the diatomic molecular quantum computer using potassium nitride and calcium nitride through vibrational progression

Dynamical entanglement of stretching–stretching and stretching–bending vibrations in SO₂

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Decoherence of intramolecular vibrational entanglement in polyatomic molecules

Cited by 7 publications

References 49 publications

Electron–vibration entanglement in the Born–Oppenheimer description of chemical reactions and spectroscopy

Electron–vibration entanglement in the Born–Oppenheimer description of chemical reactions and spectroscopy

Best molecular multiple quantum bit for the diatomic molecular quantum computer using potassium nitride and calcium nitride through vibrational progression

Dynamical entanglement of stretching–stretching and stretching–bending vibrations in SO2

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Product

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Dynamical entanglement of stretching–stretching and stretching–bending vibrations in SO₂