Quantum Engineering Laboratory
Our group studies quantum dynamics in nanoscale materials and devices using optics and electronics. We seek to better understand complex quantum-mechanical systems, with a goal of developing new technologies for communication, computation, and sensing based on quantum physics.
News
- Newton: Mimicking prions for self-replicating machines
Our paper on mechanically modeling prions is featured on Newton.
- EurekAlert!: New quantum sensing technology reveals sub-atomic signals
Our paper on nuclear quadrupolar resonance spectroscopy is featured on EurekAlert!
- Congratulations, Mathieu!
Congratulations to Mathieu on defending his PhD thesis!
Recent Publications
Sean Doan,; Patel, Sahil D.; Chen, Yilin; Gusdorff, Jordan A.; Turiansky, Mark E.; Villagomez, Luis; Jevremovic, Luka; Lewis, Nicholas; Watanabe, Kenji; Taniguchi, Takashi; Bassett, Lee C.; de Walle, Chris Van; Moody, Galan
Near-Infrared Quantum Emission from Oxygen-Related Defects in hBN Journal Article Forthcoming
In: arXiv, Forthcoming.
@article{Doan2025,
title = {Near-Infrared Quantum Emission from Oxygen-Related Defects in hBN},
author = {Sean Doan, and Sahil D. Patel and Yilin Chen and Jordan A. Gusdorff and Mark E. Turiansky and Luis Villagomez and Luka Jevremovic and Nicholas Lewis and Kenji Watanabe and Takashi Taniguchi and Lee C. Bassett and Chris Van de Walle and Galan Moody},
url = {https://arxiv.org/abs/2512.16197},
year = {2025},
date = {2025-12-18},
journal = {arXiv},
abstract = {Color centers hosted in hexagonal boron nitride (hBN) have emerged as a promising platform for single-photon emission and coherent spin-photon interfaces that underpin quantum communication and quantum networking technologies. As a wide-bandgap van der Waals material, hBN can host individual optically active quantum defects emitting across the ultraviolet to visible spectrum, but existing color centers often show broad phonon sidebands (PSBs), unstable emission, or inconvenient wavelengths. Here, we show a simple, scalable oxygen-plasma process that reproducibly creates oxygen-related single quantum emitters in hBN with blinking-free zero-phonon lines spanning the near-infrared (NIR) spectrum from 700-960 nanometers. These emitters demonstrate room-temperature operation, high brightness, and ultra-sharp cryogenic linewidths in the few-gigahertz range under non-resonant excitation. Analysis of the PSBs shows weak electron-phonon coupling and predominant zero-phonon-line emission, while first-principles calculations identify plausible oxygen-related defect configurations. These emitters provide a promising platform for indistinguishable NIR single photons towards free-space quantum networking.},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
Color centers hosted in hexagonal boron nitride (hBN) have emerged as a promising platform for single-photon emission and coherent spin-photon interfaces that underpin quantum communication and quantum networking technologies. As a wide-bandgap van der Waals material, hBN can host individual optically active quantum defects emitting across the ultraviolet to visible spectrum, but existing color centers often show broad phonon sidebands (PSBs), unstable emission, or inconvenient wavelengths. Here, we show a simple, scalable oxygen-plasma process that reproducibly creates oxygen-related single quantum emitters in hBN with blinking-free zero-phonon lines spanning the near-infrared (NIR) spectrum from 700-960 nanometers. These emitters demonstrate room-temperature operation, high brightness, and ultra-sharp cryogenic linewidths in the few-gigahertz range under non-resonant excitation. Analysis of the PSBs shows weak electron-phonon coupling and predominant zero-phonon-line emission, while first-principles calculations identify plausible oxygen-related defect configurations. These emitters provide a promising platform for indistinguishable NIR single photons towards free-space quantum networking.
Klein, Amelia R.; Austin, Hayley J.; Murakami, Fumikazu; Ford, Jamie; Tatebayashi, Jun; Tonouchi, Masayoshi; Fujiwara, Yasufumi; Dierolf, Volkmar; Bassett, Lee C.; Mitchell, Brandon
Site-selective enhancement of Eu emission in delta-doped GaN Journal Article Forthcoming
In: arXiv, Forthcoming.
@article{Klein2025,
title = {Site-selective enhancement of Eu emission in delta-doped GaN},
author = {Amelia R. Klein and Hayley J. Austin and Fumikazu Murakami and Jamie Ford and Jun Tatebayashi and Masayoshi Tonouchi and Yasufumi Fujiwara and Volkmar Dierolf and Lee C. Bassett and Brandon Mitchell},
url = {https://arxiv.org/abs/2512.15005},
year = {2025},
date = {2025-12-17},
journal = {arXiv},
abstract = {Europium-doped gallium nitride (GaN:Eu) is a promising platform for classical and quantum optoelectronic applications. When grown using organometallic vapor-phase epitaxy, the dominant red emission from Eu exhibits an inhomogeneous photoluminescence (PL) spectrum due to contributions from several non-equivalent incorporation sites that can be distinguished with combined excitation emission spectroscopy. Energy transfer from the GaN bandgap to the majority site is inefficient, limiting the performance of GaN:Eu LEDs and resulting in an inhomogeneous emission spectrum dominated by disproportionate contributions from minority sites. In this work, we use site-selective spectroscopy to characterize the photoluminescence properties of delta-doped structures with alternating doped and undoped layers of varying thicknesses and demonstrate that they selectively enhance emission from the majority site when compared to uniformly-doped samples. Samples with 2-nm and 10-nm doped layers show much greater PL intensity per Eu concentration as well as more efficient energy transfer to the majority site, which are both highly desirable for creating power-efficient LEDs. Meanwhile, a sample with 1-nm doped layers shows emission only from the majority site, resulting in a narrow, homogeneous emission spectrum that is desirable for quantum technologies. This utilization of delta-doping has the potential to be broadly applicable for engineering desirable defect properties in rare-earth doped semiconductors.},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
Europium-doped gallium nitride (GaN:Eu) is a promising platform for classical and quantum optoelectronic applications. When grown using organometallic vapor-phase epitaxy, the dominant red emission from Eu exhibits an inhomogeneous photoluminescence (PL) spectrum due to contributions from several non-equivalent incorporation sites that can be distinguished with combined excitation emission spectroscopy. Energy transfer from the GaN bandgap to the majority site is inefficient, limiting the performance of GaN:Eu LEDs and resulting in an inhomogeneous emission spectrum dominated by disproportionate contributions from minority sites. In this work, we use site-selective spectroscopy to characterize the photoluminescence properties of delta-doped structures with alternating doped and undoped layers of varying thicknesses and demonstrate that they selectively enhance emission from the majority site when compared to uniformly-doped samples. Samples with 2-nm and 10-nm doped layers show much greater PL intensity per Eu concentration as well as more efficient energy transfer to the majority site, which are both highly desirable for creating power-efficient LEDs. Meanwhile, a sample with 1-nm doped layers shows emission only from the majority site, resulting in a narrow, homogeneous emission spectrum that is desirable for quantum technologies. This utilization of delta-doping has the potential to be broadly applicable for engineering desirable defect properties in rare-earth doped semiconductors.
Minnella, Joseph D.; Ouellet, Mathieu; Klein, Amelia R.; Bassett, Lee C.
Single-gate, multipartite entanglement on a room-temperature quantum register Journal Article Forthcoming
In: arXiv, Forthcoming.
@article{Minnella2025,
title = {Single-gate, multipartite entanglement on a room-temperature quantum register},
author = {Joseph D. Minnella and Mathieu Ouellet and Amelia R. Klein and Lee C. Bassett},
url = {https://arxiv.org/abs/2508.08465},
year = {2025},
date = {2025-08-11},
urldate = {2025-08-11},
journal = {arXiv},
abstract = {Multipartite entanglement is an essential aspect of quantum systems, needed to execute quantum algorithms, implement error correction, and achieve quantum-enhanced sensing. In solid-state quantum registers such nitrogen-vacancy (NV) centers in diamond, entangled states are typically created using sequential, pairwise gates between the central electron and individual nuclear qubits. This sequential approach is slow and suffers from crosstalk errors. Here, we demonstrate a parallelized multi-qubit entangling gate to generate a four-qubit GHZ state using a room-temperature NV center in only 14.8 s 10 times faster than using sequences of two-qubit gates. The entangled states are verified by measuring multiple quantum coherences. Two-qubit entangling gates have an average fidelity of 0.96(1), and the four-qubit parallel gate has a fidelity of 0.92(4), whereas the sequential four-qubit gate fidelity is only 0.69(3). The approach is generalizable to other solid-state platforms, and it lays the foundation for scalable generation and control of entanglement in practical devices. },
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
Multipartite entanglement is an essential aspect of quantum systems, needed to execute quantum algorithms, implement error correction, and achieve quantum-enhanced sensing. In solid-state quantum registers such nitrogen-vacancy (NV) centers in diamond, entangled states are typically created using sequential, pairwise gates between the central electron and individual nuclear qubits. This sequential approach is slow and suffers from crosstalk errors. Here, we demonstrate a parallelized multi-qubit entangling gate to generate a four-qubit GHZ state using a room-temperature NV center in only 14.8 s 10 times faster than using sequences of two-qubit gates. The entangled states are verified by measuring multiple quantum coherences. Two-qubit entangling gates have an average fidelity of 0.96(1), and the four-qubit parallel gate has a fidelity of 0.92(4), whereas the sequential four-qubit gate fidelity is only 0.69(3). The approach is generalizable to other solid-state platforms, and it lays the foundation for scalable generation and control of entanglement in practical devices.
Ouellet, Mathieu; Bassett, Dani S.; Bassett, Lee C.; Murphy, Kieran A.; Patankar, Shubhankar P.
Mechanical prions as self-assembling microstructures Journal Article
In: Newton, vol. 1, iss. 5, pp. 100098, 2025.
@article{Ouellet2025,
title = {Mechanical prions as self-assembling microstructures},
author = {Mathieu Ouellet and Dani S. Bassett and Lee C. Bassett and Kieran A. Murphy and Shubhankar P. Patankar},
url = {https://www.cell.com/newton/fulltext/S2950-6360(25)00090-8
https://arxiv.org/abs/2402.10939},
year = {2025},
date = {2025-07-07},
urldate = {2025-05-08},
journal = {Newton},
volume = {1},
issue = {5},
pages = {100098},
abstract = {Prions are misfolded proteins that transmit their structural arrangement to neighboring proteins. In biological systems, prion dynamics can produce a variety of complex functional outcomes. Yet, an understanding of prionic causes has been hampered by the fact that few computational models exist that allow for experimental design, hypothesis testing, and control. Here, we identify essential prionic properties and present a biologically inspired model of prions using simple mechanical structures capable of undergoing complex conformational change. We demonstrate the utility of our approach by designing a prototypical mechanical prion and validating its properties experimentally. Our work provides a design framework for harnessing and manipulating prionic properties in natural and artificial systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Prions are misfolded proteins that transmit their structural arrangement to neighboring proteins. In biological systems, prion dynamics can produce a variety of complex functional outcomes. Yet, an understanding of prionic causes has been hampered by the fact that few computational models exist that allow for experimental design, hypothesis testing, and control. Here, we identify essential prionic properties and present a biologically inspired model of prions using simple mechanical structures capable of undergoing complex conformational change. We demonstrate the utility of our approach by designing a prototypical mechanical prion and validating its properties experimentally. Our work provides a design framework for harnessing and manipulating prionic properties in natural and artificial systems.
Panfil, Yossef E.; Thompson, Sarah M.; Chen, Gary; Ng, Jonah; Kagan, Cherie R.; Bassett, Lee C.
Room-temperature quantum emission from CuZn-VS defects in ZnS:Cu colloidal nanocrystals Journal Article
In: ACS Nano, vol. 19, iss. 23, pp. 21400-21410, 2025.
@article{Panfil2025,
title = {Room-temperature quantum emission from CuZn-VS defects in ZnS:Cu colloidal nanocrystals},
author = {Yossef E. Panfil and Sarah M. Thompson and Gary Chen and Jonah Ng and Cherie R. Kagan and Lee C. Bassett},
url = {https://pubs.acs.org/doi/abs/10.1021/acsnano.5c01265
https://arxiv.org/abs/2501.11812},
year = {2025},
date = {2025-06-05},
urldate = {2025-06-05},
journal = {ACS Nano},
volume = {19},
issue = {23},
pages = { 21400-21410},
abstract = {We report room-temperature observations of CuZn-VS quantum emitters in individual ZnS:Cu nanocrystals (NCs). Using time-gated imaging, we isolate the distinct, ∼3-μs-long, red photoluminescence (PL) emission of CuZn-VS defects, enabling their precise identification and statistical characterization. The emitters exhibit distinct blinking and photon antibunching, consistent with individual NCs containing two to four CuZn-VS defects. The quantum emitters' PL spectra show a pronounced blue shift compared to NC dispersions, likely due to photochemical and charging effects. Emission polarization measurements of quantum emitters are consistent with a σ-character optical dipole transition and the symmetry of the CuZn-VS defect. These observations motivate further investigation of CuZn-VS defects in ZnS NCs for use in quantum technologies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report room-temperature observations of CuZn-VS quantum emitters in individual ZnS:Cu nanocrystals (NCs). Using time-gated imaging, we isolate the distinct, ∼3-μs-long, red photoluminescence (PL) emission of CuZn-VS defects, enabling their precise identification and statistical characterization. The emitters exhibit distinct blinking and photon antibunching, consistent with individual NCs containing two to four CuZn-VS defects. The quantum emitters' PL spectra show a pronounced blue shift compared to NC dispersions, likely due to photochemical and charging effects. Emission polarization measurements of quantum emitters are consistent with a σ-character optical dipole transition and the symmetry of the CuZn-VS defect. These observations motivate further investigation of CuZn-VS defects in ZnS NCs for use in quantum technologies.