Optical and Magnetic Response by Design in Ga As Quantum Dots

Year: 2025

Type: article

Abstract: Quantum networking technologies use spin qubits and their interface to single photons as core components of a network node. This necessitates the ability to co-design the magnetic- and optical-dipole response of a quantum system—a capability that has been notably absent in solid-state platforms where spin-orbit coupling and the crystalline environment lead to inhomogeneity of electronic g -factors and optically active states. Here, we demonstrate the ability to design both the optical and magnetic response of a solid-state quantum emitter . We show that Ga As quantum dots (QDs), obtained via local droplet etching epitaxy and already known as exceptionally coherent and efficient quantum light sources, also exhibit spin and optical properties that follow directly from assuming the highest possible system symmetry. Our measurements of electron and hole g -tensors—using a new sign-sensitive measurement protocol based on the hyperfine interaction—and of transition dipole moment orientations for charged excitons agree with our predictions from a multiband k ⋅ p simulation constrained only by a single atomic-force-microscopy reconstruction of QD morphology. This agreement is verified across multiple wavelength-specific growth runs at different facilities within the range of 730 to 790 nm for the exciton emission. Remarkably, our measurements and simulations track the in-plane electron g -factors through a zero-crossing from − 0.1 to 0.3 and linear optical dipole moment orientations fully determined by an external magnetic field. The robustness and generality of these results establish a fundamentally new paradigm for solid-state spin-photon interfaces: one in which the properties of a spin qubit and its tunable optical interface can be designed—prior to growth—for a target magnetic and photonic environment, with direct applications to scalable and high-fidelity spin-photon entanglement.

Source: PRX Quantum

DOI: 10.1103/98cp-1k42

Institutions: University of Cambridge, Johannes Kepler University of Linz, University of Basel, University of Oxford, Universidade Estadual de Campinas (UNICAMP), Ruhr University Bochum, Quandela (France), Centre National de la Recherche Scientifique, Université Paris-Saclay, Centre de Nanosciences et de Nanotechnologies, Wrocław University of Science and Technology

Language: English

Topic: Semiconductor Quantum Structures and Devices

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,450

Funders: National Science Foundation, Royal Society, European Commission, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Fundação de Amparo à Pesquisa do Estado de São Paulo, Austrian Science Fund, Electronics and Telecommunications Research Institute, Österreichische Forschungsförderungsgesellschaft, Ministry of Science and ICT, South Korea, QuantERA, Horizon 2020 Framework Programme, Engineering and Physical Sciences Research Council, Economic and Social Research Council, Narodowe Centrum Badań i Rozwoju, Institute for Information and Communications Technology Promotion, Wroclawskie Centrum Sieciowo-Superkomputerowe, Politechnika Wroclawska

Awards: Solid state single-photon sources for telecom frequencies, G2158402412, DTP 2224 University of Oxford, Deterministic quantum gate between photons in a next-generation light-matter interface, G3112983486, G388252207, G434337789, G4561647272, G4700831490, G4787154045, G5271502856, G575169067, QuantERA II ERA-NET Cofund in Quantum Technologies, G6225469397, G6762893308, Memory-Enhanced Entanglement Distribution with Gallium ARsenide quantum Dots, Access to European Infrastructure for Nanoelectronics, G9000285978

OpenAlex ID: W4415166362