Engineering tunable anharmonic potentials with light-atom interaction for chemical dynamics simulations
Date:
Relevant papers
Anharmonicity theory preprint - coming soon!
[1] MacDonnell et al., Chem. Sci., 14, 9439 (2023)
[2] Valahu et al. Nature Chemistry 15, 1503–1508 (2023)
[3] Whitlow et al. Nature Chemistry 15, 1509–1514 (2023)
[4] Navickas et al. J. Am. Chem. Soc. (2025)
Abstract
Trapped-ion platforms have emerged as a powerful architecture for simulating quantum dynamics in chemical systems. They have enabled studies of time-resolved vibrational spectroscopy [1], geometric phase effects at conical intersections [2, 3], and classically intractable open-system dynamics [4]. However, existing implementations have been limited to harmonic oscillator models, failing to encapsulate the anharmonicity present in molecular potentials.
Here, we investigate implementing anharmonic dynamics in a trapped-ion system using all-optical quantum control. Specifically, we develop a flexible control scheme that leverages state-dependent forces and qubit rotations to engineer tunable anharmonic dynamics. As an example, we engineer a tunable double-well potential. This allows access to rich, nonlinear motional dynamics, most notably quantum tunneling between the two wells. These results establish a new pathway for simulating chemically relevant potentials in a controllable quantum platform.
Poster description
We have designed a scheme for implementing anharmonic potentials in a trapped ion system. Here we demonstrate the realisation of a double well potential, and obseve quantum tunneling between the wells.
In the first box, we outline the circuit used to generate an effective cosine Hamiltonian, with depdence on the position operator x. The quantum signal processing (QSP) sequence we use consists of a pair of state-dependent force (SDF) operators, with an intermediary singe-qubit rotation. These realise a unitary evolution with both sine and cosine dependence. Running the same sequence backwards allows us to cancel the sine terms (up to a Trotter error) and hence realise the cosine unitary. The double well requires an additional quadratic term, which we achieve by applying a detuning to the SDF (an operating in the interaction picture).
The experimental procedure is outlined in the second box. We prepare a displaced state (starting in one of the two wells) and then allow evolution under the double well Hamiltonian. Characterisation of the boson state is carried out by the Flühmann technique. We present preliminary results, with a good correspondence between the x expecation in the theory (both the solution of the master equation for the target potential and the simulation of the QSP sequence) and experiment.