Asymmetry Control in a Parametric Oscillator for the Quantum Simulation of Chemical Activation

TL;DR

This paper demonstrates a quantum simulator using a driven Kerr parametric oscillator to create a tunable asymmetric double-well, revealing new effects on tunneling rates relevant for chemical reaction modeling.

Contribution

It introduces a fully controllable asymmetric double-well system with precise measurement, enabling exploration of tunneling dynamics in quantum chemical simulations.

Findings

Weak asymmetry can decrease activation rates unexpectedly.

Tunneling resonance widths vary with well depth and asymmetry.

Numerical predictions suggest similar effects in chemical double-well systems.

Abstract

Dissipative tunneling remains a cornerstone effect in quantum mechanics. In chemistry, it plays a crucial role in governing the rates of chemical reactions, often modeled as the motion along the reaction coordinate from one potential well to another. The relative positions of energy levels in these wells strongly influence the reaction dynamics. Chemical research will benefit from a fully adjustable, asymmetric double-well equipped with precise measurement capabilities of the tunneling rates. In this paper, we show a quantum simulator system that consists of a continuously driven Kerr parametric oscillator with a third order non-linearity that can be operated in the quantum regime to create a fully tunable asymmetric double-well. Our experiment leverages a low-noise, all-microwave control system with a high-efficiency readout, based on a tunnel Josephson junction circuit, of the which-well information. We explore the reaction rates across the landscape of tunneling resonances in parameter space. We uncover two new and counter-intuitive effects: (i) a weak asymmetry can significantly decrease the activation rates, even though the well in which the system is initialized is made shallower, and (ii) the width of the tunneling resonances alternates between narrow and broad lines as a function of the well depth and asymmetry. We predict by numerical simulations that both effects will also manifest themselves in ordinary chemical double-well systems in the quantum regime. Our work is a first step for the development of analog molecule simulators of proton transfer reactions based on quantum parametric processes.