Publications

Seeking a quantum advantage with trapped-ion quantum simulations of condensed-phase chemical dynamics

MK, H. Nuomin, S.N. Chowdhury, J.L. Yuly, K. Sun, J. Whitlow, J. Valdiviezo, Z. Zhang, P. Zhang, D.N. Beratan, K.R. Brown,

Nature Reviews Chemistry, (2024). [arXiv:2305.03156]

Analog-quantum simulation derived from tracking the evolution of trapped-ion systems holds the potential to simulate molecular quantum dynamics that is beyond the reach of classical-digital strategies. This Review explores the prospects for developing this quantum advantage.

* Accepted talk at the 23rd Asian Quantum Information Science Conference (AQIS23), Seoul [Seminar]

Pulse Optimization for High-Precision Motional-Mode Characterization in Trapped-Ion Quantum Computers

Q. Liang, MK, M. Li, and Y. Nam

Quantum Science and Technology, 9, 035007 (2024). [arXiv:2307.15841]

Pulse optimization is not only for quantum gates; it can also be used for calibration (characterization of system parameters). Here we suggest using pulse optimization to characterize the motional-mode parameters (Lamb-Dicke parameters) of trapped ions with higher accuracy, which is necessary for achieving high-fidelity operations on a chain of many ions.

Quantum Error Correction with Metastable States of Trapped Ions Using Erasure Conversion

MK, W.C. Campbell, and K.R. Brown

PRX Quantum, 4, 020358 (2023). [arXiv:2210.15024]

Erasures, or errors with known locations, are more favorable than typical Pauli errors for quantum error correction. We suggest converting physical noise to erasures on trapped ions by using metastable atomic states as qubit states. Then we compare the error-correction performance of metastable and ground qubits under various physical constraints.

* Accepted talk at the 6th International Conference on Quantum Error Correction (QEC23), Sydney [Talk]

Quantum Simulation of Polarized Light-Induced Electron Transfer with a Trapped-Ion Qutrit System

K. Sun, C. Fang, MK, Z. Zhang, P. Zhang, D.N. Beratan, K.R. Brown, and J. Kim

The Journal of Physical Chemistry Letters, 14, 6071-6077 (2023). [arXiv:2304.12247]

Angle-robust Two-Qubit Gates in a Linear Ion Crystal

Z. Jia, S. Huang, MK, K. Sun, R.F. Spivey, J. Kim, and K.R. Brown

Physical Review A, 107, 032617 (2023). [arXiv:2210.04814]

Efficient Motional-Mode Characterization for High-Fidelity Trapped-Ion Quantum Computing

MK, Q. Liang, M. Li, and Y. Nam

Quantum Science and Technology, 8, 024002 (2023). [arXiv:2206.04212]

To achieve high-fidelity operations on a long ion chain, the motional-mode parameters must be efficiently characterized with high accuracy. We develop and explore physical models that accurately predict both magnitude and sign of the Lamb-Dicke parameters, as well as devise a parallelized and efficient characterization protocol.

Designing Filter Functions of Frequency-Modulated Pulses for High-Fidelity Two-Qubit Gates in Ion Chains

MK, Y. Wang, C. Fang, B. Zhang, O. Khosravani, J. Kim, and K.R. Brown

Physical Review Applied, 19, 014014 (2023). [arXiv:2206.10850]

We derive and design filter functions of the laser pulses for two-qubit gates on trapped ions, in order to suppress the effects of time-varying fluctuations of the motional-mode frequencies. This improves the experimentally measured gate fidelity from 99.23(7)% to 99.55(7)% in a five-ion chain.

Batch Optimization of Frequency-Modulated Pulses for Robust Two-Qubit Gates in Ion Chains

MK, Q. Liang, B. Zhang, S. Huang, Y. Wang, C. Fang, J. Kim, and K.R. Brown

Physical Review Applied, 16, 024039 (2021). [arXiv:2104.06887]

We apply batch optimization, a technique widely used in machine learning, to finding the laser pulses for two-qubit gates on trapped ions. We experimentally verify that the new method improves the gate’s robustness to offsets of the motional-mode frequencies.