



@article {2412,
	title = {Two-qubit entangling gates within arbitrarily long chains of trapped ions},
	year = {2019},
	month = {05/28/2019},
	abstract = {<p>Ion trap systems are a leading platform for large scale quantum computers. Trapped ion qubit crystals are fully-connected and reconfigurable, owing to their long range Coulomb interaction that can be modulated with external optical forces. However, the spectral crowding of collective motional modes could pose a challenge to the control of such interactions for large numbers of qubits. Here, we show that high-fidelity quantum gate operations are still possible with very large trapped ion crystals, simplifying the scaling of ion trap quantum computers. To this end, we present analytical work that determines how parallel entangling gates produce a crosstalk error that falls off as the inverse cube of the distance between the pairs. We also show experimental work demonstrating entangling gates on a fully-connected chain of seventeen 171Yb+ ions with fidelities as high as 97(1)\%.</p>},
	url = {https://arxiv.org/abs/1905.10421},
	author = {Kevin A. Landsman and Yukai Wu and Pak Hong Leung and Daiwei Zhu and Norbert M. Linke and Kenneth R. Brown and Luming Duan and Christopher R. Monroe}
}
@article {2052,
	title = {Robust two-qubit gates in a linear ion crystal using a frequency-modulated driving force},
	journal = {Physical Review Letters},
	volume = {120},
	year = {2018},
	month = {2018/01/09},
	pages = {020501},
	abstract = {<p>In an ion trap quantum computer, collective motional modes are used to entangle two or more qubits in order to execute multi-qubit logical gates. Any residual entanglement between the internal and motional states of the ions will result in decoherence errors, especially when there are many spectator ions in the crystal. We propose using a frequency-modulated (FM) driving force to minimize such errors and implement it experimentally. In simulation, we obtained an optimized FM gate that can suppress decoherence to less than 10\&minus;4 and is robust against a frequency drift of more than \&plusmn;1 kHz. The two-qubit gate was tested in a five-qubit trapped ion crystal, with 98.3(4)\% fidelity for a M{\o}lmer-S{\o}rensen entangling gate and 98.6(7)\% for a controlled-not (CNOT) gate. We also show an optimized FM two-qubit gate for 17 ions, proving the scalability of our method.</p>},
	doi = {10.1103/PhysRevLett.120.020501},
	url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.020501},
	author = {Pak Hong Leung and Kevin A. Landsman and Caroline Figgatt and Norbert M. Linke and Christopher Monroe and Kenneth R. Brown}
}
