Block encoding bosons by signal processing

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Main Authors: Kane, Christopher F., Hariprakash, Siddharth, Modi, Neel S., Kreshchuk, Michael, Bauer, Christian W
Format: Preprint
Published: 2024
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author Kane, Christopher F.
Hariprakash, Siddharth
Modi, Neel S.
Kreshchuk, Michael
Bauer, Christian W
author_facet Kane, Christopher F.
Hariprakash, Siddharth
Modi, Neel S.
Kreshchuk, Michael
Bauer, Christian W
contents Block Encoding (BE) is a crucial subroutine in many modern quantum algorithms, including those with near-optimal scaling for simulating quantum many-body systems, which often rely on Quantum Signal Processing (QSP). Currently, the primary methods for constructing BEs are the Linear Combination of Unitaries (LCU) and the sparse oracle approach. In this work, we demonstrate that QSP-based techniques, such as Quantum Singular Value Transformation (QSVT) and Quantum Eigenvalue Transformation for Unitary Matrices (QETU), can themselves be efficiently utilized for BE implementation. Specifically, we present several examples of using QSVT and QETU algorithms, along with their combinations, to block encode Hamiltonians for lattice bosons, an essential ingredient in simulations of high-energy physics. We also introduce a straightforward approach to BE based on the exact implementation of Linear Operators Via Exponentiation and LCU (LOVE-LCU). We find that, while using QSVT for BE results in the best asymptotic gate count scaling with the number of qubits per site, LOVE-LCU outperforms all other methods for operators acting on up to $\lesssim11$ qubits, highlighting the importance of concrete circuit constructions over mere comparisons of asymptotic scalings. Using LOVE-LCU to implement the BE, we simulate the time evolution of single-site and two-site systems in the lattice $φ^4$ theory using the Generalized QSP algorithm and compare the gate counts to those required for Trotter simulation.
format Preprint
id arxiv_https___arxiv_org_abs_2408_16824
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Block encoding bosons by signal processing
Kane, Christopher F.
Hariprakash, Siddharth
Modi, Neel S.
Kreshchuk, Michael
Bauer, Christian W
Quantum Physics
High Energy Physics - Lattice
Block Encoding (BE) is a crucial subroutine in many modern quantum algorithms, including those with near-optimal scaling for simulating quantum many-body systems, which often rely on Quantum Signal Processing (QSP). Currently, the primary methods for constructing BEs are the Linear Combination of Unitaries (LCU) and the sparse oracle approach. In this work, we demonstrate that QSP-based techniques, such as Quantum Singular Value Transformation (QSVT) and Quantum Eigenvalue Transformation for Unitary Matrices (QETU), can themselves be efficiently utilized for BE implementation. Specifically, we present several examples of using QSVT and QETU algorithms, along with their combinations, to block encode Hamiltonians for lattice bosons, an essential ingredient in simulations of high-energy physics. We also introduce a straightforward approach to BE based on the exact implementation of Linear Operators Via Exponentiation and LCU (LOVE-LCU). We find that, while using QSVT for BE results in the best asymptotic gate count scaling with the number of qubits per site, LOVE-LCU outperforms all other methods for operators acting on up to $\lesssim11$ qubits, highlighting the importance of concrete circuit constructions over mere comparisons of asymptotic scalings. Using LOVE-LCU to implement the BE, we simulate the time evolution of single-site and two-site systems in the lattice $φ^4$ theory using the Generalized QSP algorithm and compare the gate counts to those required for Trotter simulation.
title Block encoding bosons by signal processing
topic Quantum Physics
High Energy Physics - Lattice
url https://arxiv.org/abs/2408.16824