diff --git a/demonstrations/tutorial_fdhs.py b/demonstrations/tutorial_fdhs.py index 9f3c7c650c..bbefaa70d0 100644 --- a/demonstrations/tutorial_fdhs.py +++ b/demonstrations/tutorial_fdhs.py @@ -1,17 +1,25 @@ r"""Fixed Depth Hamiltonian Simulation via Cartan Decomposition =============================================================== -abstract +We introduce the powerful Lie theoretic decomposition technique for Hamiltonians, :math:`H = K h K^\dagger`, +that lets you time-evolve by arbitrary times with fixed depth, :math:`e^{-i t H} = K e^{-i t h} K^\dagger`. +In particular, we follow the approach in [#Kökcü]_ that directly provides us with a (fixed depth) circuit +decomposition of the unitaries :math:`K` and :math:`e^{-i t h}`. + +Sounds too good to be true? There are of course caveats, mostly of practical nature. +One of them is that the Lie algebra of H, in terms of which +this decomposition is based, becomes too large to handle. This is still an extremely +powerful mathematical result integral for quantum compilation, circuit optimization and Hamiltonian simulation. Introduction ------------ -The KAK theorem is an important result from Lie theory that states that any Lie group element :math:`U` can be decomposed +The :doc:`KAK theorem ` is an important result from Lie theory that states that any Lie group element :math:`U` can be decomposed as :math:`U = K_1 A K_2`, where :math:`K_{1, 2}` and :math:`A` are elements of two special sub-groups -:math:`\mathcal{K}` and :math:`\mathcal{A}`, respectively. You can think of this KAK decomposition as a generalization of -the singular value decomposition to Lie groups. +:math:`\mathcal{K}` and :math:`\mathcal{A}`, respectively. In special cases, the decomposition simplifies to :math:`U = K A K^\dagger`. -For that, recall that the singular value decomposition states that any +You can think of this KAK decomposition as a generalization of +the singular value decomposition to Lie groups. For that, recall that the singular value decomposition states that any matrix :math:`M \in \mathbb{C}^{m \times n}` can be decomposed as :math:`M = U \Lambda V^\dagger`, where :math:`\Lambda` are the diagonal singular values and :math:`U \in \mathbb{C}^{m \times \mu}` and :math:`V^\dagger \in \mathbb{C}^{\mu \times n}` are left- and right-unitary with :math:`\mu = \min(m, n)`. @@ -21,6 +29,10 @@ We can use this general result from Lie theory as a powerful circuit decomposition technique. +.. note:: We recommend a basic understanding of Lie algebras, see e.g. :doc:`our intro for quantum practitioners `. + Otherwise this demo should be self-contained. For the mathematically inclined we further recommend our :doc:`demo on the KAK theorem ` + that dives into the mathematical depths of the theorem and provides more background info. + Goal ---- @@ -422,47 +434,11 @@ def Us_kak(t): # "Fixed Depth Hamiltonian Simulation via Cartan Decomposition" # `arXiv:2104.00728 `__, 2021. # -# .. [#Wiersma] -# -# Roeland Wiersema, Efekan Kökcü, Alexander F. Kemper, Bojko N. Bakalov -# "Classification of dynamical Lie algebras for translation-invariant 2-local spin systems in one dimension" -# `arXiv:2309.05690 `__, 2023. -# -# .. [#Meyer] -# -# Johannes Jakob Meyer, Marian Mularski, Elies Gil-Fuster, Antonio Anna Mele, Francesco Arzani, Alissa Wilms, Jens Eisert -# "Exploiting symmetry in variational quantum machine learning" -# `arXiv:2205.06217 `__, 2022. -# -# .. [#Nguyen] -# -# Quynh T. Nguyen, Louis Schatzki, Paolo Braccia, Michael Ragone, Patrick J. Coles, Frederic Sauvage, Martin Larocca, M. Cerezo -# "Theory for Equivariant Quantum Neural Networks" -# `arXiv:2210.08566 `__, 2022. -# -# .. [#Fontana] -# -# Enrico Fontana, Dylan Herman, Shouvanik Chakrabarti, Niraj Kumar, Romina Yalovetzky, Jamie Heredge, Shree Hari Sureshbabu, Marco Pistoia -# "The Adjoint Is All You Need: Characterizing Barren Plateaus in Quantum Ansätze" -# `arXiv:2309.07902 `__, 2023. -# -# .. [#Ragone] -# -# Michael Ragone, Bojko N. Bakalov, Frédéric Sauvage, Alexander F. Kemper, Carlos Ortiz Marrero, Martin Larocca, M. Cerezo -# "A Unified Theory of Barren Plateaus for Deep Parametrized Quantum Circuits" -# `arXiv:2309.09342 `__, 2023. -# -# .. [#Goh] -# -# Matthew L. Goh, Martin Larocca, Lukasz Cincio, M. Cerezo, Frédéric Sauvage -# "Lie-algebraic classical simulations for variational quantum computing" -# `arXiv:2308.01432 `__, 2023. -# -# .. [#Somma] +# .. [#Chu] # -# Rolando D. Somma -# "Quantum Computation, Complexity, and Many-Body Physics" -# `arXiv:quant-ph/0512209 `__, 2005. +# Moody T. Chu +# "Lax dynamics for Cartan decomposition with applications to Hamiltonian simulation" +# `doi:10.1093/imanum/drad018 `__, `preprint PDF `__ 2024. # #