Group publications 7
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arXiv:2608.15993 (2026)
@unpublished{zhang_resolving_2026, title = {Resolving and resetting the charge environment of single T-centers in silicon p-i-n waveguides}, url = {https://arxiv.org/abs/2608.15993}, doi = {10.48550/ARXIV.2608.15993}, author = {Zhang, Chaoshen and Song, Hanbin and Komza, Lukasz and Day, Aaron M. and Garcia, Enrique and Witt, Donald and Bhaskar, Mihir K. and Sipahigil, Alp and Hu, Evelyn L.}, month = aug, year = {2026}, note = {Version Number: 1}, arxiv = {2608.15993} }The silicon T-center is a telecom-band spin-photon interface in a manufacturable photonics platform. In nanophotonic devices, however, its optical linewidth is broadened by a fluctuating charge environment, limiting photon indistinguishability for quantum networking. Here, we address this challenge through characterization and suppression of the local charge-noise of single T-centers in lateral p-i-n waveguides, demonstrating an unheralded method of T-center optical linewidth narrowing. Above-band illumination resets the charge environment, neutralizing the local field and suppressing spectral diffusion. Across 46 emitters this reset narrows the median linewidth 3.5-fold to 0.57(11) GHz, and an optimized emitter reaches 128(22) MHz, the narrowest unheralded linewidth reported for an integrated T-center. The narrowed transition supports coherent optical Rabi oscillations with a coherence time of 20(2) ns. Finally, we perform Stark-shift tuning using the p-i-n junction, and read out the local electric field and the charge-noise width at 15 mK. An analytical model of proximal surfaces, bulk, and junction field effects provides good agreement with our findings. Our multi-pronged characterization of the nanophotonic-integrated T-center charge environment enables future device optimization toward scalable quantum interconnects.
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Nature Nanotechnology 21, 53–57 (2026)
@article{song_entanglement_2026, title = {Entanglement of a nuclear spin qubit register in silicon photonics}, volume = {21}, url = {https://doi.org/10.1038/s41565-025-02066-0}, doi = {10.1038/s41565-025-02066-0}, journal = {Nature Nanotechnology}, pages = {53--57}, author = {Song, H. and Zhang, X. and Komza, L. and Fiaschi, N. and Xiong, Y. and Zhi, Y. and Dhuey, S. and Schwartzberg, A. and Schenkel, T. and Hautier, G. and Zhang, Z.-H. and Sipahigil, A.}, month = jan, year = {2026}, arxiv = {2504.15467} }Color centers provide an optical interface to quantum registers based on electron and nuclear spin qubits in solids. The T center in silicon is an emerging spin-photon interface that combines telecom O-band optical transitions and an electron spin in a scalable photonics platform. In this work, we demonstrate the initialization, coherent control, and state readout of a three-qubit register based on the electron spin of a T center coupled to a hydrogen and a silicon nuclear spin. The spin register exhibits spin echo coherence times of 0.41(2) ms for the electron spin, 112(12) ms for the hydrogen nuclear spin, and 67(7) ms for the silicon nuclear spin. We use nuclear-nuclear two-qubit gates to generate entanglement between the two nuclear spins with a fidelity of F=0.77(3) and a coherence time of T*₂=2.60(8) ms. Our results show that a T center in silicon photonics can realize a multi-qubit register with an optical interface for quantum communication.
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Optica 12, 1400 (2025)
@article{komza_multiplexed_2025, title = {Multiplexed color centers in a silicon photonic cavity array}, volume = {12}, url = {https://opg.optica.org/abstract.cfm?URI=optica-12-9-1400}, doi = {10.1364/OPTICA.564691}, journal = {Optica}, number = {9}, pages = {1400}, issn = {2334-2536}, author = {Komza, Lukasz and Zhang, Xueyue and Song, Hanbin and Tang, Yu-Lung and Wei, Xin and Sipahigil, Alp}, month = sep, year = {2025}, arxiv = {2501.17339} }Entanglement distribution is central to the modular scaling of quantum processors and establishing quantum networks. Color centers with telecom-band transitions and long spin coherence times are suitable candidates for long-distance entanglement distribution. However, high-bandwidth memory-enhanced quantum communication is limited by high-yield, scalable creation of efficient spin-photon interfaces. Here, we develop a silicon photonics platform consisting of arrays of bus-coupled cavities. The coupling to a common bus waveguide enables simultaneous access to individually addressable cavity-enhanced T center arrays. We demonstrate frequency-multiplexed operation of two T centers in separate photonic crystal cavities. In addition, we investigate the cavity enhancement of a T center through hybridized modes formed between physically distant cavities. Our results show that bus-coupled arrays of cavity-enhanced color centers could enable efficient on-chip and long-distance entanglement distribution.
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arXiv:2501.11888 (2025)
@unpublished{day_probing_2025, title = {Probing negative differential resistance in silicon with a P-I-N diode-integrated T center ensemble}, url = {http://arxiv.org/abs/2501.11888}, doi = {10.48550/arXiv.2501.11888}, author = {Day, Aaron M. and Zhang, Chaoshen and Jin, Chang and Song, Hanbin and Sutula, Madison and Sipahigil, Alp and Bhaskar, Mihir K. and Hu, Evelyn L.}, month = jan, year = {2025}, note = {arXiv:2501.11888 [quant-ph]}, arxiv = {2501.11888} }The T center in silicon has recently emerged as a promising candidate for scalable quantum technologies, due to its telecommunications band optical transition and microwave addressable ground state spin. The immense promise of the T center is driven by its silicon host material; silicon is by far the most mature, manufacturable semiconductor material for integrated photonic and electronic devices. Here, we present the first study of T-centers in an electrical device. We study an ensemble of T centers coupled to a buried lateral P-I-N diode in silicon, observing the T-center’s optical response to static and dynamic electric fields. We utilize the defect’s optical response as a probe of device nonlinearity, observing a phase transition of the carrier density into a stable oscillatory regime characteristic of negative differential resistance. These findings provide fundamental insight into the physics of the T-center for improved quantum device performance and open a promising new direction for defect-based local quantum sensing in semiconductor devices.
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PRX Quantum 6, 030351 (2025)
@article{zhang_laser-induced_2025, title = {Laser-{Induced} {Spectral} {Diffusion} of T {Centers} in {Silicon} {Nanophotonic} {Devices}}, volume = {6}, url = {https://doi.org/10.1103/x2cv-2gcw}, doi = {10.1103/x2cv-2gcw}, journal = {PRX Quantum}, pages = {030351}, author = {Zhang, X. and Fiaschi, N. and Komza, L. and Song, H. and Schenkel, T. and Sipahigil, A.}, year = {2025}, arxiv = {2504.08898} }Color centers in silicon are emerging as spin-photon interfaces operating at telecommunication wavelengths. The nanophotonic device integration of silicon color centers via ion implantation leads to significant optical-linewidth broadening, which makes indistinguishable photon generation challenging. Here, we study the optical spectral diffusion of T centers in a silicon photonic crystal cavity. We investigate the linewidth-broadening timescales and origins by measuring the temporal correlations of the resonance frequency under different conditions. Spectral hole-burning measurements reveal no spectral broadening at short timescales from 102 ns to 725 ns. We probe broadening at longer timescales using a check pulse to herald the T-center frequency and a probe pulse to measure the frequency after a wait time. The optical resonance frequency is stable up to 3 ms in the dark. Laser pulses below the silicon band gap applied during the wait time lead to linewidth broadening. Our observations establish laser-induced processes as the dominant spectral-diffusion mechanism for T centers in devices and inform materials and feedback strategies for indistinguishable photon generation.
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Nature Communications 15, 6920 (2024)
@article{komza_indistinguishable_2024, title = {Indistinguishable photons from an artificial atom in silicon photonics}, volume = {15}, url = {https://www.nature.com/articles/s41467-024-51265-1}, doi = {10.1038/s41467-024-51265-1}, journal = {Nature Communications}, number = {1}, pages = {6920}, issn = {2041-1723}, author = {Komza, Lukasz and Samutpraphoot, Polnop and Odeh, Mutasem and Tang, Yu-Lung and Mathew, Milena and Chang, Jiu and Song, Hanbin and Kim, Myung-Ki and Xiong, Yihuang and Hautier, Geoffroy and Sipahigil, Alp}, month = aug, year = {2024}, arxiv = {2211.09305} }Abstract Silicon is the ideal material for building electronic and photonic circuits at scale. Integrated photonic quantum technologies in silicon offer a promising path to scaling by leveraging advanced semiconductor manufacturing and integration capabilities. However, the lack of deterministic quantum light sources and strong photon-photon interactions in silicon poses a challenge to scalability. In this work, we demonstrate an indistinguishable photon source in silicon photonics based on an artificial atom. We show that a G center in a silicon waveguide can generate high-purity telecom-band single photons. We perform high-resolution spectroscopy and time-delayed two-photon interference to demonstrate the indistinguishability of single photons emitted from a G center in a silicon waveguide. Our results show that artificial atoms in silicon photonics can source single photons suitable for photonic quantum networks and processors.
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Science Advances 9, eadh8617 (2023)
@article{xiong_high-throughput_2023, title = {High-throughput identification of spin-photon interfaces in silicon}, volume = {9}, url = {https://www.science.org/doi/10.1126/sciadv.adh8617}, doi = {10.1126/sciadv.adh8617}, journal = {Science Advances}, number = {40}, pages = {eadh8617}, issn = {2375-2548}, author = {Xiong, Yihuang and Bourgois, Céline and Sheremetyeva, Natalya and Chen, Wei and Dahliah, Diana and Song, Hanbin and Zheng, Jiongzhi and Griffin, Sinéad M. and Sipahigil, Alp and Hautier, Geoffroy}, month = oct, year = {2023}, arxiv = {2303.01594} }Color centers in host semiconductors are prime candidates as spin-photon interfaces for quantum applications. Finding an optimal spin-photon interface in silicon would move quantum information technologies toward a mature semiconducting host. However, the space of possible charged defects is vast, making the identification of candidates from experiments alone extremely challenging. Here, we use high-throughput first-principles computational screening to identify spin-photon interfaces among more than 1000 charged defects in silicon. The use of a single-shot hybrid functional approach is critical in enabling the screening of many quantum defects with a reasonable accuracy. We identify three promising spin-photon interfaces as potential bright emitters in the telecom band: T i i + , F e i 0 , and R u i 0 . These candidates are excited through defect-bound excitons, stressing the importance of such defects in silicon for telecom band operations. Our work paves the way to further large-scale computational screening for quantum defects in semiconductors. , First principles screening reveals three quantum defect candidates in silicon for spin-photon interfaces.
* Equal contribution