Optically Active Single Hole Spin in ZnSe

arXiv:2607.00110 · quant-ph · Submitted 2026-06-30 · Read on arXiv

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Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: I'm Kai.

Mira: And I'm Mira, here with Lev.

Kai: Today's paper: "Optically Active Single Hole Spin in ZnSe".

Mira: The gist: The study reports optical activation and isolation of shallow acceptor-bound hole spins in ZnSe quantum well,

Kai: First, who's behind it and why it matters.

Paper summary: Kai: So to recap, this paper, "Optically Active Single Hole Spin in ZnSe," tackles how to get extended coherence times for hole spins by decoupling them from nuclear magnetic noise using their spin-orbit coupling for fast all electrical control.

Mira: And the core problem they were solving was the difficulty realizing this potential in ZnSe because of those p-doping challenges that limit this pathway.

Lev: The thesis is that they found a way around that by optically activating acceptors within the ZnSe quantum well to isolate a single hole spin.

Kai: They claim they successfully isolate one hole spin bound to a shallow acceptor, and they access it through the fast two four four picosecond radiative recombination of a bound exciton.

Mira: The findings suggest nitrogen is the most likely acceptor impurity because first principles simulations showed nitrogen substituting on the Se site, NSe, emerges as the most likely candidate.

Lev: This is important because it provides a specific impurity to look for when trying to build real hardware based on this concept.

Kai: It matters because these results introduce a promising new platform for optically active spin qubits and single photon sources in ZnSe.

Mira: So the big picture is that they’ve opened up a new route for using holes in these materials for quantum applications, specifically things involving light and spin control.

Conclusion: Kai: So looking at the title, "Optically Active Single Hole Spin in ZnSe," it really tells you that the method used light to create a controllable spin system where before it was hard to get one.

Mira: And when you look at the authors, you see a collaboration between experimentalists like Kai and hardware builders, and theorists like Lev and Mira who did those first principles simulations.

Lev: The implication for real hardware is that they have identified a specific defect, nitrogen in ZnSe, which means we don't have to guess what impurity we are dealing with.

Kai: So if you only listen to the show, it means that for quantum photonics applications using ZnSe, optical activation is a viable way forward for handling these hole spins.

Mira: And this suggests that they can use light not just to create the spin state but also to actively manage its presence and control its dynamics in a way that was previously hard to achieve.

Institute for Research in Electronics and Applied Physics and Joint Quantum Institute, University of Maryland Department of Electrical and Computer Engineering, University of Maryland Department of Materials Science and Engineering, Peter-Grünberg Institute Forschungszentrum Jülich GmbH JARA-Fundamentals of Future Information Technology Forschungszentrum Jülich RWTH Aachen University

quant-ph

Submitted: 2026-06-30

Updated: 2026-08-03

DOI: 10.1021/acs.nanolett.6c03982

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Importance score: 67/100

The gist: The gist: The study reports optical activation and isolation of shallow acceptor-bound hole spins in ZnSe quantum well, establishing a promising new platform for optically active spin qubits and

Key concepts

Hole Spin Coherence: Hole spins are beneficial because their orbital symmetry helps them ignore noise from nuclear spins, leading to longer coherence times. This extended coherence is crucial for using them in quantum computing applications where maintaining spin information over time is essential.
Optical Activation: The study used above-band optical charge injection to neutralize 'dark' acceptor impurities. This process turns a normally inactive impurity into an optically active one, enabling researchers to manipulate and observe the spin state using light, which was key to isolating the single hole spin.
g-factor and Linewidth: The effective g-factor of 0.7 describes how strongly the hole's magnetic moment responds to external magnetic fields. The optical resonance linewidth of 26.7 GHz provides information about the local environment, showing that charge fluctuations cause spectral diffusion, which limits coherence.
Acceptor Impurity (Nitrogen): First-principles calculations indicated that nitrogen substituting on the Se site (NSe) is the most likely acceptor impurity in ZnSe because it forms a shallow state with an ionization energy of 0.16 eV, matching experimental localization energy observations.

Terminology

Decoupling — 1× in this paper · explained in 2 episodes

Summary

The gist: The study reports optical activation and isolation of shallow acceptor-bound hole spins in ZnSe quantum well, establishing a promising new platform for optically active spin qubits and single-photon sources in ZnSe.

Introduction and Motivation

Impurity-bound excitons in ZnSe provide bright single-photon emission and a promising spin-photon platform for quantum photonics. Hole spins benefit from a p-orbital symmetry that suppresses hyperfine interactions with nuclear spins, promising extended coherence times. Furthermore, their strong spin-orbit coupling enables fast all-electrical spin manipulation. The localization of the bound hole in acceptors inside the quantum well results in a more reproducible potential landscape and higher homogeneity compared to well-known quantum dot systems.

Identification of the Acceptor Impurity

First-principles calculations for various impurities identified as likely being present in the growth reactor were performed, and among those considered, nitrogen substituting on the Se site (NSe) emerged as the most likely acceptor-type defect in ZnSe. Nitrogen forms the shallowest acceptor state in ZnSe with an ionization energy of 0.16 eV. The average localization energy of 33.9±7.9 meV is most consistent with NSe, whose shallow acceptor level aligns well with the observed values. This suggests that nitrogen is the most likely candidate for the isolated single-hole spin.

Optical Activation and Characterization

The paper achieves this by neutralizing the optically dark acceptor via above-bandgap optical charge injection. This is confirmed through quasi-resonant excitation experiments where the acceptor emission is present only with the co-application of an above-band pump. The bound exciton emission exhibits a fast component with an average decay time of 256 ps, consistent with values reported for nitrogen acceptors. Verification of the single-photon nature is achieved via pulsed laser autocorrelation measurements, yielding a corrected value of g(2)(0) ≈ 0.05, confirming that the emission originates from a single isolated defect.

Spin Manipulation and Linewidth Analysis

Polarization-resolved magnetospectroscopy yielded an effective hole g-factor of 0.7 and an optical resonance linewidth of 26.7 GHz. Spin-flip Raman spectroscopy confirmed that the transitions are interconnected through a Λ-system and provided qualitative evidence for optical hole spin initialization. The linewidth of 111 µeV, which is about 40 times larger than the lifetime-limited linewidth (0.65 GHz), is attributed to spectral diffusion caused by charge fluctuations in the local trap environment.

Charge Dynamics Model

A rate-equation model was derived to analyze the photoluminescence excitation intensity as a function of above-band and resonant excitation powers. The model describes the population dynamics of three distinct charge states: A−⟩, A0⟩, and A0X⟩. The measured intensity I is described by the equation I(PABE) = η kREPRE / [1 + kREPRE/Γrad + (Γcap + kionPRE) / (kABEPABE + kleakPRE)]. This model confirms that PABE acts to supply the ground state A0⟩ against depletion, while PRE acts to both drive the A0X⟩ transition and, at high powers, depopulate the A0⟩ state via ionization.

Conclusion and Future Directions

The results confirm that optical activation and isolation of shallow acceptor-bound hole spins in ZnSe quantum well is achievable. Future efforts should focus on stabilizing this environment and implementing coherent control. A practical next step is the integration of the quantum well into a Schottky diode structure on a p-doped GaAs substrate. This architecture would allow for the application of vertical electric fields to suppress charge noise via carrier depletion while electrically neutralizing the acceptor. Furthermore, such electrical gating could be leveraged to drive fast electric dipole spin resonance.

Acknowledgments and Data Availability

The Waks group would like to acknowledge support from the AFOSR (grant FA95502010250, grant FA95542410266, and grant FA955310667). All of the data that support the findings of this study are reported in the main text and Supplementary Materials. The authors declare that they have no competing interests.

Author Contributions

A.A., A.P., and E.W. conceived the experiment. C.F., N.D., and Y.K. fabricated the device. A single hole spin bound to a nitrogen acceptor within ZnSe quantum well was isolated. K.M. and D.I. provided the first principle simulations and analysis of this theoretical data. A single hole spin bound to a nitrogen acceptor within ZnSe quantum well was isolated. All authors discussed the results and confirmed the manuscript. E.W. and A.P. supervised the experiment.

References

[3] Yuxi Jiang, C Falter, R M Pettit, N von den Driesch, Y Kutovyi, A A Herfati, A Pawlis, and E Waks “Coherent emission from single impurities in znse through resonant excitation” arXiv preprint arXiv:2412.01677 2024]

[5] N E Kopteva, E Kirstein, E A Zhukov, M Hussain, A S Bhatti, A Pawlis, D R Yakovlev, M Bayer and A Greilich “Spin dephasing of electrons and holes in isotopically purified znse/(Zn Mg)se quantum wells” Physical Review B vol 100 no 20 p 205415 2019]

[7] E Kirstein, E A Zhukov, D S Smirnov, V Nedelea, P Greve, I V Kalitukha, V F Sapega, A Pawlis, D R Yakovlev, M Bayer and A Greilich “Extended spin coherence of the zinc-vacancy centers in znse with fast optical access” Communications Materials vol 2 p 91 sep 2021]

[8] Y Kutovyi, M M Jansen, S Qiao, C Falter, N von den Driesch, T Brazda, N Demarina, S Trellenkamp, B Bennemann D Grützmacher and A Pawlis “Efficient Single-Photon Sources Based on Chlorine-Doped ZnSe Nanopillars with Growth Controlled Emission Energy” ACS Nano vol 16 pp 14582–14589 Sept 2022]

[9] K De Greve, S M Clark, D Sleiter, K Sanaka, T D Ladd, M Panfilova, A Pawlis, K Lischka and Y Yamamoto “Photon antibunching and magnetospectroscopy of a single fluorine donor in ZnSe” Applied Physics Letters vol 97 p 241913 Dec 2010]

[15] A Alizadehherfati, Y Jiang, N v d Driesch, C Falter, Y Kutovyi, J R Basani, A Boreiri, A Pawlis and E Waks “Electrical control of optically active single spin qubits in znse” arXiv preprint arXiv:2512.21462 2025]

[30]

Improvements for AI systems

textbf Rewriting Materials Science Simulation Models for Defect Identification: The AI system can accurately predict the most likely acceptor impurity by incorporating results from Complementary firstprinciples simulations, together with the experimental results, specifically linking nitrogen as the most likely acceptor impurity based on calculated formation energies and observed localization energy of 33.9 ± 7.9 meV.
textbf Developing High-Fidelity Spectroscopic Interpretation: The AI system can perform automated analysis of photoluminescence excitation spectra by fitting them to the derived standard two-level saturation model (Eq. S12), allowing it to distinguish between the effects of above-band excitation and resonant laser drives on charge state dynamics.
textbf Modeling Spin Dynamics and Coherence: The system can simulate fast spin-flip process as an indication of spin initialization by solving the Steady-State Rate Equations (S3–S6), thereby predicting the effective hole g-factor of 0.7 and the average optical lifetime of 244 ± 29 ps.
textbf Predicting Spectral Diffusion Limitations: The AI can quantify decoherence mechanisms by analyzing the optical resonance linewidth, extracting a value of 111 µeV, and attributing it to spectral diffusion caused by charge fluctuations in the local trap environment.
textbf Designing Optimized Quantum Device Architectures: Based on findings, the system can suggest next steps like integrating the quantum well into a Schottky diode structure on a p-doped GaAs substrate to suppress charge noise via carrier depletion and drive fast electric dipole spin resonance.