Shallow-Depth Quantum Circuit for Unstructured Database Search
Grover’s search algorithm (GSA) offers quadratic speedup in searching unstructured databases but suffers from exponential circuit depth complexity. Here, we present two quantum circuits called HX and Ry layers for the searching problem. Remarkably, both circuits maintain a fixed circuit depth of two...
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MDPI AG
2024-10-01
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| Series: | Quantum Reports |
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| author | Junpeng Zhan |
| author_facet | Junpeng Zhan |
| author_sort | Junpeng Zhan |
| collection | DOAJ |
| description | Grover’s search algorithm (GSA) offers quadratic speedup in searching unstructured databases but suffers from exponential circuit depth complexity. Here, we present two quantum circuits called HX and Ry layers for the searching problem. Remarkably, both circuits maintain a fixed circuit depth of two and one, respectively, irrespective of the number of qubits used. When the target element’s position index is known, we prove that either circuit, combined with a single multi-controlled <i>X</i> gate, effectively amplifies the target element’s probability to over 0.99 for any qubit number greater than seven. To search unknown databases, we use the depth-1 Ry layer as the <i>ansatz</i> in the Variational Quantum Search (VQS), whose efficacy is validated through numerical experiments on databases with up to 26 qubits. The VQS with the Ry layer exhibits an exponential advantage, in circuit depth, over the GSA for databases of up to 26 qubits. |
| format | Article |
| id | doaj-art-6912e1abd6364ca6aee3971562f718e3 |
| institution | OA Journals |
| issn | 2624-960X |
| language | English |
| publishDate | 2024-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Quantum Reports |
| spelling | doaj-art-6912e1abd6364ca6aee3971562f718e32025-08-20T02:01:21ZengMDPI AGQuantum Reports2624-960X2024-10-016455056310.3390/quantum6040037Shallow-Depth Quantum Circuit for Unstructured Database SearchJunpeng Zhan0Department of Renewable Energy Engineering, Alfred University, Alfred, NY 14802, USAGrover’s search algorithm (GSA) offers quadratic speedup in searching unstructured databases but suffers from exponential circuit depth complexity. Here, we present two quantum circuits called HX and Ry layers for the searching problem. Remarkably, both circuits maintain a fixed circuit depth of two and one, respectively, irrespective of the number of qubits used. When the target element’s position index is known, we prove that either circuit, combined with a single multi-controlled <i>X</i> gate, effectively amplifies the target element’s probability to over 0.99 for any qubit number greater than seven. To search unknown databases, we use the depth-1 Ry layer as the <i>ansatz</i> in the Variational Quantum Search (VQS), whose efficacy is validated through numerical experiments on databases with up to 26 qubits. The VQS with the Ry layer exhibits an exponential advantage, in circuit depth, over the GSA for databases of up to 26 qubits.https://www.mdpi.com/2624-960X/6/4/37Grover’s search algorithmsearch unstructured databasesvariational quantum search |
| spellingShingle | Junpeng Zhan Shallow-Depth Quantum Circuit for Unstructured Database Search Quantum Reports Grover’s search algorithm search unstructured databases variational quantum search |
| title | Shallow-Depth Quantum Circuit for Unstructured Database Search |
| title_full | Shallow-Depth Quantum Circuit for Unstructured Database Search |
| title_fullStr | Shallow-Depth Quantum Circuit for Unstructured Database Search |
| title_full_unstemmed | Shallow-Depth Quantum Circuit for Unstructured Database Search |
| title_short | Shallow-Depth Quantum Circuit for Unstructured Database Search |
| title_sort | shallow depth quantum circuit for unstructured database search |
| topic | Grover’s search algorithm search unstructured databases variational quantum search |
| url | https://www.mdpi.com/2624-960X/6/4/37 |
| work_keys_str_mv | AT junpengzhan shallowdepthquantumcircuitforunstructureddatabasesearch |