Arbitrary state creation via controlled measurement

Fuente: arXiv
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Auteurs principaux: Zenchuk, Alexander I., Qi, Wentao, Wu, Junde
Format: Preprint
Publié: 2025
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author Zenchuk, Alexander I.
Qi, Wentao
Wu, Junde
author_facet Zenchuk, Alexander I.
Qi, Wentao
Wu, Junde
contents The initial state creation is a starting point of many quantum algorithms and usually is considered as a separate subroutine not included into the algorithm itself. There are many algorithms aimed on creation of special class of states. Our algorithm allows creating an arbitrary $n$-qubit pure quantum superposition state with precision of $m$-decimals (binary representation) for each probability amplitude. The algorithm uses one-qubit rotations, Hadamard transformations and C-NOT operations with multi-qubit controls. However, the crucial operation is the final controlled measurement of the ancilla state that removes the garbage part of the superposition state and allows to avoid the problem of small success probability in that measurement. We emphasize that rotation angles are predicted in advance by the required precision and therefore there is no classical calculation supplementing quantum algorithm. The depth and space of the algorithm growth with $n$ as, respectively, $O(2^n n)$ and $O(n)$. This algorithm can be a subroutine generating the required input state in various algorithms, in particular, in matrix-manipulation algorithms developed earlier.
format Preprint
id arxiv_https___arxiv_org_abs_2504_09462
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Arbitrary state creation via controlled measurement
Zenchuk, Alexander I.
Qi, Wentao
Wu, Junde
Quantum Physics
Mathematical Physics
The initial state creation is a starting point of many quantum algorithms and usually is considered as a separate subroutine not included into the algorithm itself. There are many algorithms aimed on creation of special class of states. Our algorithm allows creating an arbitrary $n$-qubit pure quantum superposition state with precision of $m$-decimals (binary representation) for each probability amplitude. The algorithm uses one-qubit rotations, Hadamard transformations and C-NOT operations with multi-qubit controls. However, the crucial operation is the final controlled measurement of the ancilla state that removes the garbage part of the superposition state and allows to avoid the problem of small success probability in that measurement. We emphasize that rotation angles are predicted in advance by the required precision and therefore there is no classical calculation supplementing quantum algorithm. The depth and space of the algorithm growth with $n$ as, respectively, $O(2^n n)$ and $O(n)$. This algorithm can be a subroutine generating the required input state in various algorithms, in particular, in matrix-manipulation algorithms developed earlier.
title Arbitrary state creation via controlled measurement
topic Quantum Physics
Mathematical Physics
url https://arxiv.org/abs/2504.09462