diff --git a/demonstrations/tutorial_how_to_build_vibrational_hamiltonians.json b/demonstrations/tutorial_how_to_build_vibrational_hamiltonians.json new file mode 100644 index 0000000000..0ce642fe81 --- /dev/null +++ b/demonstrations/tutorial_how_to_build_vibrational_hamiltonians.json @@ -0,0 +1,67 @@ +{ + "title": "How to build vibrational Hamiltonians", + "authors": [ + { + "username": "ddhawan" + }, + { + "username": "austingmhuang" + }, + { + "username": "soran" + } + ], + "dateOfPublication": "2025-07-10T00:00:00+00:00", + "dateOfLastModification": "2025-07-10T00:00:00+00:00", + "categories": [ + "Getting Started", + "How-to" + ], + "tags": [], + "previewImages": [ + { + "type": "thumbnail", + "uri": "/_static/demo_thumbnails/regular_demo_thumbnails/thumbnail_how_to_build_spin_hamiltonians.png" + }, + { + "type": "large_thumbnail", + "uri": "/_static/demo_thumbnails/large_demo_thumbnails/thumbnail_large_how_to_build_spin_hamiltonians.png" + } + ], + "seoDescription": "Learn how to build vibrational Hamiltonians with PennyLane.", + "doi": "", + "references": [ + { + "id": "loaiza", + "type": "article", + "title": "Simulating near-infrared spectroscopy on a quantum computer for enhanced chemical detection", + "authors": "I. Loaiza *et al.*", + "journal": "arXiv:2504.10602", + "year": "2025", + "url": "https://arxiv.org/abs/2504.10602" + }, + { + "id": "motlagh", + "type": "article", + "title": "Quantum Algorithm for Vibronic Dynamics: Case Study on Singlet Fission Solar Cell Design", + "authors": "D. Motlagh *et al.*", + "journal": "arXiv:2411.13669", + "year": "2024", + "url": "https://arxiv.org/abs/2411.13669" + } + ], + "basedOnPapers": [], + "referencedByPapers": [], + "relatedContent": [ + { + "type": "demonstration", + "id": "tutorial_quantum_chemistry", + "weight": 1.0 + }, + { + "type": "demonstration", + "id": "tutorial_how_to_build_spin_hamiltonians", + "weight": 1.0 + } + ] +} diff --git a/demonstrations/tutorial_how_to_build_vibrational_hamiltonians.py b/demonstrations/tutorial_how_to_build_vibrational_hamiltonians.py new file mode 100644 index 0000000000..5f0fbb1282 --- /dev/null +++ b/demonstrations/tutorial_how_to_build_vibrational_hamiltonians.py @@ -0,0 +1,203 @@ +r"""How to build vibrational Hamiltonians +========================================= +Vibrational motions are crucial for describing the quantum properties of molecules and +materials. Molecular vibrations can affect the outcome of chemical reactions and there are several +vibrational spectroscopy techniques that provide valuable insight into understanding chemical +systems and processes [#loaiza]_ [#motlagh]_. Classical quantum +computations have been routinely implemented to describe vibrational motions of molecules. However, +for challenging vibrational systems, classical methods typically have fundamental theoretical +limitations that prevent their practical implementation. This makes quantum algorithms an ideal +choice where classical methods are not efficient or accurate. + +Quantum algorithms require a precise description of the system Hamiltonian to compute vibrational +properties. In this demo, we learn how to use PennyLane features to construct and manipulate +different representations of vibrational Hamiltonians. We also briefly discuss the implementation of +the Hamiltonian in an interesting quantum algorithm for computing the vibrational dynamics of a +molecule. + +.. figure:: ../_static/demo_thumbnails/opengraph_demo_thumbnails/OGthumbnail_how_to_build_spin_hamiltonians.png + :align: center + :width: 70% + :target: javascript:void(0) +""" + +###################################################################### +# Vibrational Hamiltonian +# ----------------------- +# A molecular vibrational Hamiltonian can be defined in terms of the kinetic energy operator of the +# nuclei, :math:`T`, and the potential energy operator, :math:`V`, which describes the interactions +# between the nuclei as: +# +# .. math:: +# +# H = T + V. +# +# The kinetic and potential energy operators can be written in terms of momentum and position +# operators, respectively. There are several ways to construct the potential energy operator which +# lead to different representations of the vibrational Hamiltonian. Here we explain some of these +# representations and provide PennyLane codes for constructing them. +# +# Christiansen representation +# ^^^^^^^^^^^^^^^^^^^^^^^^^^^ +# The Christiansen representation of the vibrational Hamiltonian relies on the n-mode expansion of +# the potential energy surface :math:`V` over vibrational normal coordinates :math:`Q`. +# +# .. math:: +# +# V({Q}) = \sum_i V_1(Q_i) + \sum_{ij} V_2(Q_i,Q_j) + ..., +# +# This provides a general representation of the potential energy surface where the terms :math:`V_n` +# depend on :math:`n` vibrational modes at most. +# +# The Christiansen Hamiltonian is then constructed in second-quantization based on this potential +# energy surface in terms of bosonic creation :math:`b^{\dagger}` and annihilation :math:`b` +# operations: +# +# .. math:: +# +# H = \sum_{i}^M \sum_{k_i, l_i}^{N_i} C_{k_i, l_i}^{(i)} b_{k_i}^{\dagger} b_{l_i} + +# \sum_{i`__ in PennyLane +# provides a set of tools that can be used to construct several representations of vibrational +# Hamiltonians. Here we learned how to use these tools to build vibrational Hamiltonians +# step-by-step and also use the PennyLane built-in functions to easily construct the Hamiltonians in +# one step. The qchem module provides +# `features `__ +# for constructing a vibrational potential energy surface efficiently using parallel executor +# options. The modular design of the vibrational features also facilitate further extension of the +# tools to support building other Hamiltonian types and representations and develop novel mapping +# methods intuitively. +# +# References +# ---------- +# +# .. [#loaiza] +# +# I. Loaiza *et al.*, +# "Simulating near-infrared spectroscopy on a quantum computer for enhanced chemical detection", +# arXiv:2504.10602, 2025. +# +# .. [#motlagh] +# +# D. Motlagh *et al.*, +# "Quantum Algorithm for Vibronic Dynamics: Case Study on Singlet Fission Solar Cell Design", +# arXiv:2411.13669, 2024. +# +# About the authors +# ----------------- +#