arXiv subjects

Xun Ji

Publications and source records attributed to Xun Ji.

3 recordsLinked to original sources

arXiv2026

Dissipative acousto-mechanical parametric interface between high-overtone acoustics and flexural phonons

High-overtone bulk acoustic wave resonators (HBARs) promise advanced phononics, yet achieving nonlinearity remains challenging. We demonstrate a radiation-pressure-type parametric interaction between GHz HBARs and low-frequency flexural modes in a suspended silicon nitride membrane, where mechanical displacement modulates the external dissipation rate to enable dissipative acousto-mechanical coupling. Benefiting from the high quality factor, the system enters the resolved-sideband regime at room temperature, yielding acousto-mechanically induced transparency. We observe tunable Kerr nonlinearity and generate coherent HBAR frequency combs via two-tone driving. Notably, our dissipative coupling strength is 20 times larger than the dispersive coupling, the highest ratio among reported hybrid dissipative-dispersive coupling systems, resulting in the experimental observation of amplification in the reflection spectra under red-sideband driving. The ability to interface dense HBAR modes with a common mechanical resonator provides a scalable on-chip platform for multimode phononic information processing, with quantum phononics potentially achievable at sub-Kelvin temperatures.

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arXiv2024

Quantum Sparse Coding and Decoding Based on Quantum Network

Sparse coding provides a versatile framework for efficiently capturing and representing crucial data (information) concisely, which plays an essential role in various computer science fields, including data compression, feature extraction, and general signal processing. In this study, we propose a symmetric quantum neural network for realizing sparse coding and decoding algorithms. Our networks consist of multi-layer, two-level unitary transformations that are naturally suited for optical circuits. Each gate is described by two real parameters, corresponding to reflectivity and phase shift. Specifically, the two networks can be efficiently trained together or separately using a quantum natural gradient descent algorithm, either simultaneously or independently. Utilizing the trained model, we achieve sparse coding and decoding of binary and grayscale images in classical problems, as well as that of complex quantum states in quantum problems separately. The results demonstrate an accuracy of 98.77\% for image reconstruction and a fidelity of 97.68\% for quantum state revivification. Our quantum sparse coding and decoding model offers improved generalization and robustness compared to the classical model, laying the groundwork for widespread practical applications in the emerging quantum era.

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arXiv2024

Image Compression and Reconstruction Based on Quantum Network

Quantum network is an emerging type of network structure that leverages the principles of quantum mechanics to transmit and process information. Compared with classical data reconstruction algorithms, quantum networks make image reconstruction more efficient and accurate. They can also process more complex image information using fewer bits and faster parallel computing capabilities. Therefore, this paper will discuss image reconstruction methods based on our quantum network and explore their potential applications in image processing. We will introduce the basic structure of the quantum network, the process of image compression and reconstruction, and the specific parameter training method. Through this study, we can achieve a classical image reconstruction accuracy of 97.57\%. Our quantum network design will introduce novel ideas and methods for image reconstruction in the future.

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