Quantum simulation of molecular vibronic spectrum and quantum Rabi model with trapped ion system

Prof. Kihwan Kim (Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University,)

In the quite near future, a quantum computer capable of handling 50-100 qubits would be expected to be developed. Such quantum computer is large enough to be impossible to be simulated by existing classical computers, but it may not be sufficient to perform the full quantum error correction and to execute Shor algorithms. Therefore, it is an important question at this stage to find something meaningful tasks with such levels of quantum computers. In this seminar, I’d like to show that an analogue quantum simulation can be a promising solution to perform beyond classical computation by discussing two examples of experimental demonstrations that we’ve recently conducted in our simple system. The first is the quantum simulation of molecular vibronic spectrum lead by Yangchao Shen [1]. This simulation is a modification of the boson sampling algorithm, which is suitable for showing the power of a quantum computer. Thought the boson sampling algorithm is difficult to perform any useful tasks, by modifying the boson sampling protocol we are able to compute the molecular vibronic spectrum [2]. The trapped ion demonstration employs phonons that can deterministically prepared and detected, which would allow us the sampling of vibronic spectrum beyond photonic systems. The second is the quantum simulation of quantum Rabi model demonstrated by Dingshun Lv [3]. Currently, the realizations of quantum simulation have been mostly limited to spin models. The quantum Rabi model is the most fundamental model that describes the interaction between spin and field. In particular, when the interaction strength is comparable or larger than the field frequency, various exotic phenomena and ground state entanglement can be occurred, which is observed in our trapped ion quantum simulator. The current experimental demonstrations are limited to small systems, but we expect that as the system grows, it will provide solutions that exceed the existing limitations without the requirement of full quantum error corrections. [1] Yangchao Shen, et al., Quantum simulation of molecular spectroscopy in trapped-ion device, Chemical Science DOI: 10.1039/C7SC04602B (2018). [2] J. Huh, et al., Boson sampling for molecular vibronic spectra, Nature Photon. 9, 615 (2015). [3] Dingshun Lv, et al., Quantum simulation of the quantum Rabi model in a trapped ion, arXiv:1711.00582 (2017).

Seminar Room, Serrano 113b