A tunable chiral light-matter interface with on-chip spin control
Abstract
The ability to engineer chiral light-matter interactions is a valuable resource for realizing quantum networks and non-reciprocal quantum optics. Here, we demonstrate chiral coupling between light and a negatively charged exciton state, i.e., a four-level system, embedded in a standard photonic-crystal waveguide. By controlling the orientation and strength of an external magnetic field, we tune the polarization of the individual optical transition dipoles relative to the fixed elliptically polarized waveguide mode. In a two-sided waveguide, an optimized oblique magnetic field allows a selected transition to decay exclusively into a single propagation direction, enabling near-unity directional emission (0.99+0.01−0.02), despite the waveguide exhibiting imperfect polarization for chiral coupling. We further observe two tunable chiral branching ratios, the directional analogue of optical cyclicity, for two Λ-systems, with one reaching 134−77+∞. The magnetic-field-dependent spectroscopy also allows reconstruction of the local guided-mode polarization at the emitter via the Stokes parameters relative to the emitter's dipole moments. Finally, we demonstrate that this local chirality enables coherent control of an electron spin via an optical Raman process mediated by waveguide driving. Building on the simultaneous realization of a large branching ratio, directionality and spin control achieved at the same oblique magnetic-field angle, we propose a protocol with high tolerance to photon loss for generating high-fidelity remote spin-spin entanglement. Our magnetic control opens a reconfigurable and generic route for enhancing on-chip chiral spin-photon coupling in standard nanophotonic interfaces without the need to carefully engineer the polarization of the waveguide.
Related
- Dynamically modulated light-matter interactions for ancilla-tolerant bosonic control
- Tremaine-Gunn Control: Evading Bounds on Light Fermion Dark Matter
- Tunable flat bands from a parent chiral Hamiltonian
- Tunable slow-light waveguide achieved by magneto-photonic crystals
- Bicircular light tunable topological phases and nonlinear Hall responses in odd-parity magnets
BibTeX
@misc{liu2026tunable,
title = {{A tunable chiral light-matter interface with on-chip spin control}},
author = {Shikai Liu and Joan Alba and Bálint Sárközi and Nikolai Bart and Arne Ludwig and Ming Lai Chan and Peter Lodahl and Anders S. Sørensen},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.06630},
eprint = {2609.06630},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.06630},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A tunable chiral light-matter interface with on-chip spin control
AU - Shikai Liu
AU - Joan Alba
AU - Bálint Sárközi
AU - Nikolai Bart
AU - Arne Ludwig
AU - Ming Lai Chan
AU - Peter Lodahl
AU - Anders S. Sørensen
PY - 2026
DA - 2026/09/06
PB - arXiv
DO - 10.48550/arxiv.2609.06630
UR - https://arxiv.org/abs/2609.06630
AB - The ability to engineer chiral light-matter interactions is a valuable resource for realizing quantum networks and non-reciprocal quantum optics. Here, we demonstrate chiral coupling between light and a negatively charged exciton state, i.e., a four-level system, embedded in a standard photonic-crystal waveguide. By controlling the orientation and strength of an external magnetic field, we tune the polarization of the individual optical transition dipoles relative to the fixed elliptically polarized waveguide mode. In a two-sided waveguide, an optimized oblique magnetic field allows a selected transition to decay exclusively into a single propagation direction, enabling near-unity directional emission (0.99^+0.01_−0.02), despite the waveguide exhibiting imperfect polarization for chiral coupling. We further observe two tunable chiral branching ratios, the directional analogue of optical cyclicity, for two Λ-systems, with one reaching 134_−77^+∞. The magnetic-field-dependent spectroscopy also allows reconstruction of the local guided-mode polarization at the emitter via the Stokes parameters relative to the emitter's dipole moments. Finally, we demonstrate that this local chirality enables coherent control of an electron spin via an optical Raman process mediated by waveguide driving. Building on the simultaneous realization of a large branching ratio, directionality and spin control achieved at the same oblique magnetic-field angle, we propose a protocol with high tolerance to photon loss for generating high-fidelity remote spin-spin entanglement. Our magnetic control opens a reconfigurable and generic route for enhancing on-chip chiral spin-photon coupling in standard nanophotonic interfaces without the need to carefully engineer the polarization of the waveguide.
ER -