Improving Scalability of Trapped-Ion Quantum Computers Using Gate-Level Techniques
| dc.contributor.advisor | Kim, Jungsang | |
| dc.contributor.author | Fang, Chao | |
| dc.date.accessioned | 2023-06-08T18:24:50Z | |
| dc.date.available | 2023-06-08T18:24:50Z | |
| dc.date.issued | 2023 | |
| dc.department | Electrical and Computer Engineering | |
| dc.description.abstract | Trapped ions provide a promising platform to build a practical quantum computer. Scaling the high performance of small systems to longer ion chains is a technical endeavor that benefits from both better hardware system design and gate-level control techniques. In this thesis, I discuss our work on building a small-scale trapped-ion quantum computing system that features stable laser beam control, low-crosstalk individual addressing and capability to implement high-fidelity multi-qubit gates. We develop control techniques to extend the pack-leading fidelity of entangling gates in two-ion systems to longer chains. A major error source limiting entangling gate fidelities in ion chains is crosstalk between target and neighboring spectator qubits. We propose and demonstrate a crosstalk suppression scheme that eliminates all first-order crosstalk utilizing only local control of target qubits, as opposed to an existing scheme which requires control over all neighboring qubits. Using the scheme, we achieve a $99.5\%$ gate fidelity in a 5-ion chain. Complex quantum circuits can benefit from native multi-qubit gates such as the $N$-Toffoli gate, which substantially reduce the overhead cost from performing universal decomposition into single- and two-qubit gates. We take advantage of novel performance benefits of long ion chains to realize scalable Cirac-Zoller gates, which uses a simple pulse sequence to efficiently implement $N$-Toffoli gates. We demonstrate the Cirac-Zoller 3- and 4-Toffoli gates in a five-ion chain with higher fidelities than previous results using trapped ions. We also present the first experimental realization of a 5-Toffoli gate. | |
| dc.identifier.uri | ||
| dc.subject | Quantum physics | |
| dc.subject | Atomic physics | |
| dc.subject | Applied physics | |
| dc.subject | atomic molecular and optical physics | |
| dc.subject | ion trap | |
| dc.subject | Quantum computing | |
| dc.subject | quantum control | |
| dc.subject | quantum gates | |
| dc.subject | Quantum information | |
| dc.title | Improving Scalability of Trapped-Ion Quantum Computers Using Gate-Level Techniques | |
| dc.type | Dissertation |