Theoretical Analysis Demonstrates Photonic Resonances in Kerr Nonlinear Resonators with Detuning Set to Times Kerr Nonlinearity

Understanding the behaviour of Kerr parametric oscillators, devices with potential applications in information processing, presents a significant challenge for modern physics, and researchers are continually seeking ways to fully characterise their properties. Yuki Tanaka from Chuo University, alongside Aiko Yamaguchi, Tomohiro Yamaji, and colleagues at the National Institute of Advanced Industrial Science and Technology and Tokyo University of Science, now shed light on a puzzling phenomenon observed during spectroscopic measurements of these resonators, photonic resonance. The team demonstrates that this resonance, which occurs even when conventional spectroscopic conditions are not met, arises not from a direct transition between energy levels, but from subtle, higher-order effects. Through detailed theoretical calculations and simulations incorporating realistic decoherence, they reveal that these effects induce oscillations between energy states, ultimately giving rise to the observed photonic resonance and deepening our understanding of these complex systems.

The study addresses the complexities arising from the interplay between linear and nonlinear optical phenomena within these resonant structures, which significantly affects the interpretation of spectroscopic data. Through detailed theoretical analysis, the team elucidates how the Kerr nonlinearity modifies the spectral response of the resonator, enabling more precise characterisation of material properties and device performance. Spectroscopic measurements provide a powerful means of elucidating detailed information about the system, such as its energy-level structure.

Tunable KPOs Demonstrate Quantum State Control

This research focuses on Kerr-nonlinear parametric oscillators (KPOs) and their potential applications in quantum technologies, particularly quantum computation and simulation. The work explores the dynamics, control, and potential for creating complex quantum states within these oscillators. A key finding is the ability to precisely control energy levels within KPOs through multiple tunable degeneracies, crucial for creating specific quantum states. Researchers aim to manipulate and stabilise quantum states within the KPO, including cat qubits and other complex states, while investigating the role of dissipation in the system.

They are exploring how dissipation can be harnessed or mitigated to improve quantum state control, with the ultimate goal of building robust and scalable quantum systems based on these oscillators. This work aims to leverage these KPOs for quantum computation, quantum simulation, quantum annealing, quantum readout, and parametric amplification. The research combines theoretical modelling with experimental investigations, revealing novel phenomena like pairwise level degeneracies and an Arrhenius law in the quantum regime. Researchers are deeply investigating the physics of KPOs, focusing on precise control of energy levels and stabilisation of quantum states.

Higher-Order Perturbation Drives Photonic Resonance

This research elucidates the mechanism behind photonic resonance observed in Kerr parametric oscillator spectroscopy, resolving a long-standing question about how resonance arises even when direct transitions are forbidden. Scientists demonstrated, through both theoretical calculations and experiments, that photonic resonance indeed occurs, and confirmed qualitative agreement between predictions and observations. Detailed analysis revealed that, despite an initially zero transition matrix element, higher-order perturbative effects induce Rabi oscillations between energy levels, effectively enabling transitions. Numerical simulations, incorporating the effects of decoherence, further confirmed that these coherent oscillations decay, manifesting as photonic resonance.

The team extended this understanding by showing that Rabi oscillations occur not only between adjacent energy levels, but also between higher-order degenerate states, a phenomenon previously unobserved. Researchers acknowledge that the analysis relies on approximations and that a complete understanding of decoherence requires further investigation. Future work could focus on exploring the limits of these perturbative calculations and developing more sophisticated models to account for environmental effects. This research provides a fundamental advance in understanding nonlinear optical systems and opens new avenues for exploring and controlling light-matter interactions in complex systems.