SKKU Researchers Identify Room-Temperature “Spin Qubit” Defect in Zinc Oxide Semiconductors
SKKU Researchers Identify Room-Temperature “Spin Qubit” Defect in Zinc Oxide Semiconductors
The computational workflow of defect candidate search with critical parameters.
An international research team led by Professor Hosung Seo at Sungkyunkwan University (SKKU)—in collaboration with researchers at the University of Wisconsin–Madison and the University of Washington—has computationally identified a novel atomic defect in zinc oxide (ZnO) capable of functioning as a high-fidelity “spin qubit.” Published in PRX Quantum, the findings propose a molybdenum-oxygen-vacancy complex [(MoZnvO)2+] as an optically addressable, deep-level spin-triplet defect. The discovery marks the first time a robust, room-temperature spin qubit has been identified in ZnO, a wide-bandgap semiconductor already deeply integrated into global commercial fabrication processes.
Overcoming the Diamond NV-Center Manufacturing Bottleneck
Currently, the nitrogen-vacancy (NV) center in diamond is the gold standard for solid-state spin qubits because it can retain quantum information at room temperature. However, diamond is notoriously difficult to grow as large-area single crystals and is fundamentally incompatible with standard CMOS manufacturing techniques. Zinc oxide offers a highly compelling alternative: it can be grown via Molecular Beam Epitaxy (MBE) as ultra-high-purity, large-area wafers and is naturally “magnetically quiet” (oxygen isotopes are 99.7% free of nuclear spin, reducing decoherence noise).
While shallow donor defects (like Indium or Gallium) have previously been studied in ZnO, their low binding energy restricts operation to cryogenic temperatures and limits emission to the UV spectrum. In contrast, the newly identified deep-level (MoZnvO)2+ defect features localized spin-triplet ground states that provide superior thermal stability.
First-Principles Design and Defect Characterization
Using state-of-the-art Density Functional Theory (DFT) and Green’s function (GW) simulations, the team systematically screened substitutional defects across the periodic table, ultimately focusing on the molybdenum substitution. The resulting (MoZnvO)2+ complex exhibited three critical physical properties essential for a viable quantum light source and spin-photon interface:
Suppressed Phonon Coupling (HR Factor): The defect demonstrated an exceptionally small Huang-Rhys (HR) factor of ∼5, compared to 10–30 for previously known ZnO defects. This results in minimal energy leakage into crystal lattice vibrations (phonons) during photon emission, yielding a sharp, high-efficiency zero-phonon line (ZPL) in the visible spectrum.
Millisecond Spin Coherence (T2): First-principles calculations predict that the electron spin can maintain coherence for roughly 4 milliseconds (T2 ≈ 4 ms), limited primarily by paramagnetic impurity concentrations rather than intrinsic lattice noise.
High-Fidelity Single-Shot Readout: The defect features strong spin-orbit coupling (SOC) combined with a suppressed Jahn-Teller distortion. This unique electronic geometry enables spin-selective intersystem crossing (ISC), allowing researchers to accurately read the qubit’s spin state in a single optical measurement even at elevated temperatures—a critical requirement for quantum error correction logic.
By establishing a theoretical pathway to scalable, room-temperature spin qubits in a standard oxide semiconductor, the SKKU-led team aims to accelerate the mass production of integrated quantum networks and ultra-sensitive solid-state quantum sensors.
Read the full open-access theoretical paper, “Deep Spin Defects in Zinc Oxide for High-Fidelity Single-Shot Readout,” published in PRX Quantum here. For broader university highlights, review the summary on the SKKU Research Hub here.
July 25, 2026
Mohamed Abdel-Kareem2026-07-25T06:16:55-07:00
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