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arXiv · 2402.04212

Preparing general mixed quantum states on quantum computers

Lucas Friedrich·Douglas F. Pinto·Diego S. Starke·Jonas Maziero
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Abstract

The preparation of quantum states is a fundamental subroutine for a broad class of quantum information protocols and is critical for both quantum communication and quantum computation. Building upon the quantum algorithms introduced in previous works [M. B. Pozzobom and J. Maziero, Quantum Inf. Process. 18, 142 (2019)] and [E. R. G\aa rding \textit{et al.}, Entropy 23, 797 (2021)], the authors of [F. Shahbeigi, M. Karimi and V. Karimipour, Phys. Scr. 97, 025101 (2022)] demonstrated the capability to prepare mixed two-qubit X-real states on quantum computers by extending the methodology originally devised for mixed two-qubit Bell diagonal states. In this article, we delve into an overlooked pattern within these quantum circuits, allowing us to present a modular algorithm for the preparation of general $d$-dimensional mixed quantum states using quantum information processors. Our general algorithm has a modular structure, encompassing eigenvalue encoding, entropy injection, and eigenvector preparation. To validate our algorithm, we conduct tests on quantum computers utilizing both X- and non X-states for two mixed-state qubits, two-ququart Bell-diagonal states, as well as arbitrary random density matrices spanning one, two, and three qubits.

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Lucas Friedrich, Douglas F. Pinto, Diego S. Starke, Jonas Maziero. 2024-02-06. Preparing general mixed quantum states on quantum computers. https://doi.org/10.1007/s11128-026-05299-7

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