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1. Dynamic Nuclear Polarization Enhanced Nuclear Spin Optical Rotation

   https://doi.org/10.1002/anie.202016412  

   Zhu, Yue; Hilty, Christian; Savukov, Igor (March 2021, Angewandte Chemie International Edition)

   Abstract Nuclear spin optical rotation (NSOR) has been investigated as a magneto‐optical effect, which holds the potential for applications, including hybrid optical‐nuclear magnetic resonance (NMR) spectroscopy and gradientless imaging. The intrinsic nature of NSOR renders its detection relatively insensitive, which has prevented it moving from a proof of concept to a method supporting chemical characterizations. In this work, the dissolution dynamic nuclear polarization technique is introduced to provide nuclear spin polarization, increasing the signal‐to‐noise ratio by several thousand times. NSOR signals of¹H and¹⁹F nuclei are observed in a single scan for diluted compounds, which has made this effect suitable for the determination of electronic transitions from a specific nucleus in a large molecule. 

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2. Parallel single-shot measurement and coherent control of solid-state spins below the diffraction limit

   https://doi.org/10.1126/science.abc7821  

   Chen, Songtao; Raha, Mouktik; Phenicie, Christopher M.; Ourari, Salim; Thompson, Jeff D. (October 2020, Science)

   Solid-state spin defects are a promising platform for quantum science and technology. The realization of larger-scale quantum systems with solid-state defects will require high-fidelity control over multiple defects with nanoscale separations, with strong spin-spin interactions for multi-qubit logic operations and the creation of entangled states. We demonstrate an optical frequency-domain multiplexing technique, allowing high-fidelity initialization and single-shot spin measurement of six rare-earth (Er³⁺) ions, within the subwavelength volume of a single, silicon photonic crystal cavity. We also demonstrate subwavelength control over coherent spin rotations by using an optical AC Stark shift. Our approach may be scaled to large numbers of ions with arbitrarily small separation and is a step toward realizing strongly interacting atomic defect ensembles with applications to quantum information processing and fundamental studies of many-body dynamics. 

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3. Hybrid microwave-optical scanning probe for addressing solid-state spins in nanophotonic cavities

   https://doi.org/10.1364/OE.417528  

   Chen, Songtao; Ourari, Salim; Raha, Mouktik; Phenicie, Christopher_M; Uysal, Mehmet_T; Thompson, Jeff_D (February 2021, Optics Express)

   Spin-photon interfaces based on solid-state atomic defects have enabled a variety of key applications in quantum information processing. To maximize the light-matter coupling strength, defects are often placed inside nanoscale devices. Efficiently coupling light and microwave radiation into these structures is an experimental challenge, especially in cryogenic or high vacuum environments with limited sample access. In this work, we demonstrate a fiber-based scanning probe that simultaneously couples light into a planar photonic circuit and delivers high power microwaves for driving electron spin transitions. The optical portion achieves 46% one-way coupling efficiency, while the microwave portion supplies an AC magnetic field with strength up to 9 Gauss at 10 Watts of input microwave power. The entire probe can be scanned across a large number of devices inside a³He cryostat without free-space optical access. We demonstrate this technique with silicon nanophotonic circuits coupled to single Er³⁺ions. 

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4. Entanglement of nanophotonic quantum memory nodes in a telecom network

   https://doi.org/10.1038/s41586-024-07252-z  

   Knaut, C M; Suleymanzade, A; Wei, Y-C; Assumpcao, D R; Stas, P-J; Huan, Y Q; Machielse, B; Knall, E N; Sutula, M; Baranes, G; et al (May 2024, Nature)

   Abstract A key challenge in realizing practical quantum networks for long-distance quantum communication involves robust entanglement between quantum memory nodes connected by fibre optical infrastructure^1–3. Here we demonstrate a two-node quantum network composed of multi-qubit registers based on silicon-vacancy (SiV) centres in nanophotonic diamond cavities integrated with a telecommunication fibre network. Remote entanglement is generated by the cavity-enhanced interactions between the electron spin qubits of the SiVs and optical photons. Serial, heralded spin-photon entangling gate operations with time-bin qubits are used for robust entanglement of separated nodes. Long-lived nuclear spin qubits are used to provide second-long entanglement storage and integrated error detection. By integrating efficient bidirectional quantum frequency conversion of photonic communication qubits to telecommunication frequencies (1,350 nm), we demonstrate the entanglement of two nuclear spin memories through 40 km spools of low-loss fibre and a 35-km long fibre loop deployed in the Boston area urban environment, representing an enabling step towards practical quantum repeaters and large-scale quantum networks. 

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5. Simultaneous Incorporation of Magnetic and Plasmonic Nanocrystals in a Chiral Conducting Polymer Yields Unprecedented Magneto‐Optic Response

   https://doi.org/10.1002/smll.202409752  

   Abraham, Shema; Dutta, Avisek; Joseph, Jojo P; Rajapakse, B Medini; Baev, Alexander; Zeng, Hao; Velarde, Luis; Prasad, Paras N; Swihart, Mark T (March 2025, Small)

   Abstract The creation of next‐generation flexible and conformable magneto‐optic (MO) materials with dramatically enhanced Verdet constant will significantly advance technologies, including optical isolation, magnetic quantum spin fluctuation measurements, and cold atom spin coherence probes, while opening new possibilities for mapping weakly emanating magnetic fields from sources, including microelectronics or brain activity. The results presented here show that the natural coupling of electric and magnetic dipoles in a chiral polymer with large optical activity (circular birefringence) is significantly enhanced by combined plasmonic field and magnetic interactions of plasmonic nanostars and magnetic nanoparticles to yield a dramatically increased Verdet constant within an optical path of a few hundred nanometers. A 175 ± 10 nm film of this material produces up to 600 mdeg of relative MO rotation at 510 nm, which translates to a record‐high Verdet constant of 3.1 × 10⁷deg T⁻¹m⁻¹at 93 K, more than two orders of magnitude higher than the current state of the art MO garnet crystals. The room temperature Verdet constant substantially exceeds that of other thin film nanocomposites reported to date. Manipulation of electric and magnetic coupling offers an unprecedented opportunity to tailor the magnitude, sign, and spectral dispersion of the Verdet constant over a broad range of wavelengths. 

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