Quantum Hybrid Systems Demonstrate Photon-Tunneling Modulation with Four Discrete Chiral Orientations

The manipulation of light at the nanoscale holds immense promise for future photonic technologies, and researchers are now exploring how closely spaced chiral structures influence the behaviour of photons. Aryan Pratap Srivastava, Moulik Deviprasad Ketkar, and Kuldeep Kumar Shrivastava, all from the Indian Institute of Technology (Banaras Hindu University), alongside colleagues, demonstrate a significant advance in controlling photon tunneling between pairs of specially designed microwave resonators. Their work reveals that by carefully adjusting the distance between these chiral structures, they can strongly modulate the transmission of light, creating interference effects and even ‘dark states’ where light is suppressed. This ability to control photon flow through structural design, and the observation of behaviour mirroring quantum systems in a classical setting, suggests exciting possibilities for reconfigurable photonic devices and advanced applications in chiral sensing and signal processing.

Chiral Metamaterials for Quantum Light Control

This research explores the manipulation of light using chiral metamaterials, structures lacking mirror symmetry that offer unique ways to control light’s properties and interaction with matter. The work focuses on split-ring resonators, artificial structures interacting strongly with electromagnetic waves, to create environments influencing single photons and enabling quantum devices. A key goal is achieving non-reciprocal light propagation, where light travels differently depending on direction, enabling optical isolators and directional devices. The team demonstrates that carefully designed chiral metamaterials effectively control light’s polarization, direction, and quantum state, enhancing light-matter interactions and improving quantum efficiency, ultimately providing building blocks for future quantum computers and communication networks.

The researchers utilize concepts from circuit quantum electrodynamics, connecting classical electromagnetism with quantum mechanics, to model and understand the behavior of these metamaterials. This approach describes light’s interaction with the structures in terms of quantum circuits, providing a powerful tool for designing and optimizing quantum devices, with potential to revolutionize quantum computing, communication, and create advanced optical signal processing, highly sensitive sensors, and secure communication systems. The team investigates parity-time symmetry, balancing gain and loss to create unique optical properties, and employs tight-binding models to describe the metamaterials’ electronic structure. The research focuses on achieving non-reciprocity without magnetic materials, a significant advantage, and explores integrating perovskite materials with metamaterials to create even more advanced optical devices, while acknowledging challenges in fabrication, loss reduction, and scaling up production for large-scale quantum circuits.

Chirality and Proximity Control Hybridization of Resonators

Scientists have demonstrated precise control over photon tunneling between coupled microwave resonators, each possessing four distinct chiral orientations. By varying the spacing between these resonators, they observed significant changes in light transmission, including mode splitting, interference effects, and the formation of dark states, indicative of strong hybridization, confirmed by electromagnetic simulations. To describe these observations, the team developed a circuit electrodynamics model, building upon coupled-mode theory and classical dipole interactions, extending these approaches to capture geometry-dependent coupling strength and its potential reversal. Employing circuit quantum electrodynamics, the model compactly describes photon tunneling, mode hybridization, and chirality-dependent coupling, remaining consistent with classical observations.

This framework was extended to incorporate a third spectral branch, arising from incoherent processes such as mode interference and decoherence, providing a unified quantum description of all observed spectral features. The team modeled the system using a Hamiltonian describing two identical resonating modes, coupled through a coefficient dependent on distance and relative orientation, incorporating a dimensionless angular prefactor derived through iterative modeling and refinement of measured splitting data. The coupling coefficient was expressed as a product of this angular prefactor and an exponential term describing evanescent photon tunneling, ensuring dimensional consistency, and allowing calculation of the transmission spectrum using the Heisenberg, Langevin formalism, validating the model against experimental results.

Chiral Resonator Coupling Controls Photon Tunneling

Scientists have demonstrated strong modulation of photon tunneling within a pair of coupled microwave resonators, achieving control through manipulation of their chiral orientation and spacing. Varying the distance between the resonators revealed distinct phenomena including mode splitting, interference effects, and the formation of dark states, with hybridization dependent on both chirality and proximity, confirmed by full-wave electromagnetic simulations. To describe the observed behavior, the team developed a circuit electrodynamics model accurately capturing the dependence of coupling strength on the geometry of the resonators, predicting a reversal of coupling sign. Although the experimental excitation was classical, the system reproduces features expected from two quantized harmonic oscillators, establishing a classical analogue of a chiral hybrid platform.

Simulations revealed that at a relative chiral angle of 180 degrees, strong photon-mediated interactions resulted in hybridized mode formation and distinct resonant peaks at small resonator separations. As the inter-resonator spacing increased, dipolar field overlap diminished, leading to weaker coupling and convergence of the split resonances. Experimental validation on 32 designs confirmed the simulation results and demonstrated the tunability of photon tunneling, establishing chirality as a control parameter for manipulating mode interactions and opening possibilities for reconfigurable photonic devices, chiral sensing, and polarization-selective signal processing.

Tunable Photon Tunneling via Chirality and Phase

This research demonstrates precise control of photon tunneling within chiral microwave resonators, achieved through careful engineering of both the physical orientation and excitation phase of the system. Scientists developed a framework to manipulate light-matter interactions by exploiting quantum interference effects in these specially designed structures. Measurements on fabricated devices confirm that the coupling between resonators is highly sensitive to these parameters, even reversing sign beyond a specific orientation, and this behavior is accurately predicted by a newly developed circuit electrodynamics model. The team’s findings validate the possibility of dynamically modulating light using compact photonic platforms, opening avenues for applications such as phase-programmable isolators, dark-state filters, and reconfigurable resonator arrays, and supporting the potential development of chiral qudit logic and coherent quantum photonics.