BELT: Block Encoding of Linear Transformation on Density Matrices

Fuente: arXiv
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Hauptverfasser: Wei, Fuchuan, Lu, Rundi, Shao, Yuguo, Li, Junfeng, Liu, Jin-Peng, Liu, Zhengwei
Format: Preprint
Veröffentlicht: 2025
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author Wei, Fuchuan
Lu, Rundi
Shao, Yuguo
Li, Junfeng
Liu, Jin-Peng
Liu, Zhengwei
author_facet Wei, Fuchuan
Lu, Rundi
Shao, Yuguo
Li, Junfeng
Liu, Jin-Peng
Liu, Zhengwei
contents Linear maps that are not completely positive play a crucial role in the study of quantum information, yet their non-completely positive nature renders them challenging to realize physically. The core difficulty lies in the fact that when acting such a map $\mathcal{N}$ on a state $ρ$, $\mathcal{N}(ρ)$ may not correspond to a valid density matrix, making it difficult to prepare directly in a physical system. We introduce Block Encoding of Linear Transformation (BELT), a systematic protocol that simulates arbitrary linear maps by embedding the output $\mathcal{N}(ρ)$ into a block of a unitary operator. BELT enables the manipulation and extraction of information about $\mathcal{N}(ρ)$ through coherent quantum evolution. Notably, BELT accommodates maps that fall outside the scope of quantum singular value transformation, such as the transpose map. BELT finds applications in entanglement detection, quantum channel inversion, and simulating pseudo-differential operators, and demonstrates improved sample complexity compared to protocols based on Hermitian-preserving map exponentiation.
format Preprint
id arxiv_https___arxiv_org_abs_2508_12858
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle BELT: Block Encoding of Linear Transformation on Density Matrices
Wei, Fuchuan
Lu, Rundi
Shao, Yuguo
Li, Junfeng
Liu, Jin-Peng
Liu, Zhengwei
Quantum Physics
Linear maps that are not completely positive play a crucial role in the study of quantum information, yet their non-completely positive nature renders them challenging to realize physically. The core difficulty lies in the fact that when acting such a map $\mathcal{N}$ on a state $ρ$, $\mathcal{N}(ρ)$ may not correspond to a valid density matrix, making it difficult to prepare directly in a physical system. We introduce Block Encoding of Linear Transformation (BELT), a systematic protocol that simulates arbitrary linear maps by embedding the output $\mathcal{N}(ρ)$ into a block of a unitary operator. BELT enables the manipulation and extraction of information about $\mathcal{N}(ρ)$ through coherent quantum evolution. Notably, BELT accommodates maps that fall outside the scope of quantum singular value transformation, such as the transpose map. BELT finds applications in entanglement detection, quantum channel inversion, and simulating pseudo-differential operators, and demonstrates improved sample complexity compared to protocols based on Hermitian-preserving map exponentiation.
title BELT: Block Encoding of Linear Transformation on Density Matrices
topic Quantum Physics
url https://arxiv.org/abs/2508.12858