Predicting molecular vibronic spectra using time-domain analog quantum simulation

Direct observation of geometric-phase interference in dynamics around a conical intersection

“…Like any analog simulation-quantum or classicalour approach is ultimately limited by noise and uncorrected errors. In our experiment, the main sources of decoherence and dissipation are motional dephasing and motional heating [39,49] (see Methods). However, in MQB simulations of molecular processes, noise can be characterised and even amplified in order to create a realistic model of molecular environments, such as collisions in solution.…”

“…Motional heating was caused by electric field noise at the radial mode frequency, while motional dephasing arose from fluctuations in the harmonic trapping potential strength [53]. We measured the heating rate and the motional dephasing time of B 1 (representative for both modes) to be ṅ = 0.2 quanta s −1 and T * 2 = 35 ms [39]. The motional coherence was limited by noise in the radio frequency (RF) trapping voltage, which was actively stabilised to mitigate fluctuations in the radial mode frequencies.…”

“…The data quality of the reconstructed densities depends on correctly setting the laser frequencies for the motional sideband interactions that enact SDF interactions. The motional frequencies ω 1 and ω 2 associated with B 1 and B 2 are calibrated as previously reported [39]. To do so, both SDF interactions are applied, but we set the fields associated with ω 2 to be sufficiently off resonant while calibrating ω 1 .…”

“…We realise a conical intersection using an 171 Yb + ion confined in a Paul trap, where two vibrations are encoded directly in the ion's transverse vibrational modes (B 1 and B 2 ), while two electronic states are encoded in the ion's qubit (qudit with d = 2) states comprising the two hyperfine levels of the 2 S 1/2 ground state (detailed in Methods). This approach has recently been employed to predict molecular spectra using time-domain simulations [39], and provides resource-scaling advantages relative to conventional methods of quantum simulation [38].…”