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

Alejandro Cros Carrillo de Albornoz1,2,*,†, Rodrigo G. Cortiñas1,*,‡,§, Max Schäfer1,*,‖,¶, Nicholas E. Frattini1,**, Brandon Allen3, Delmar G.A. Cabral3, Pablo E. Videla3, Pouya Khazaei4, Eitan Geva4 et al.

Victor S. Batista3 and Michel H. Devoret1,††,‡‡

  • *These authors contributed equally to this work.
  • †Contact author: a.croscarrillo@gmail.com
  • ‡Present address: Google Quantum AI, Santa Barbara, CA, USA.
  • §Contact author: rodrigogc@google.com
  • ‖Present address: Department of Physics, University of California, Santa Barbara, CA, USA.
  • Contact author: maxschaefer@ucsb.edu
  • **Present address: Nord Quantique, Sherbrooke, QC J1J 2E2, Canada.
  • ††Present addresses: Google Quantum AI, Santa Barbara, CA, USA and Department of Physics, University of California, Santa Barbara, CA, USA.
  • ‡‡Contact author: devoret@ucsb.edu
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PRX Quantum 7, 020309 – Published 16 April, 2026

DOI: https://doi.org/10.1103/71yp-fqns

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 nonlinearity 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 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.

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synopsis

Quantum Circuit Simulates Chemistry

Published 16 April, 2026

A tunable quantum device can model the energy profiles of chemical reactions and improve physicists’ understanding of reaction dynamics.

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Whether it is catalysis or a biological switching in DNA, complex chemical dynamics may be modified by subtle quantum interference effects occurring in a reaction’s energy landscape. Predicting and controlling these effects are of both fundamental and practical importance. A minimal model for such chemical reaction systems is an energy landscape with two wells separated by a barrier. We have developed a microwave-controlled superconducting quantum circuit that realizes such a model. Unlike natural molecules, our circuit lets us independently dial in barrier height and differential well depth. This precise control revealed two surprising effects. First, the switching rates show “breathing” resonances that alternate between narrow and broad as the well asymmetry is varied. Second, tailored asymmetry can slow down switching even when the initial well is shallower. This work confirms the power of superconducting circuits as quantum simulators of the natural world.

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PRX Quantum 7, 020309– Published 16 April, 2026
  • Received 8 May 2025
  • Revised 22 January 2026
  • Accepted 25 February 2026
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