Introduction
In the swiftly expanding realm of quantum technologies, nanodiamonds have emerged as a vanguard material, holding enormous potential for applications in quantum information processing, quantum optics, and quantum sensing. Key to unlocking this potential is the ability to produce high-quality nanodiamonds with consistent sizes and embedded single quantum emitters, such as nitrogen vacancy (NV) centers. Against this backdrop, a collaborative team of researchers has made significant strides by devising a novel top-down fabrication technique that ingeniously harnesses the self-assembly characteristics of block copolymers to create uniform nanodiamonds integrated with bright single nitrogen vacancy centers. Published in Scientific Reports, this study outlines a revolutionary approach to synthesize uniformly-sized, non-aggregated single-crystal nanodiamonds, a critical step that could catapult quantum technologies into a new era.
Quantum technology is an exhilarating frontier—one in which nanodiamonds are set to play a starring role. These diminutive diamonds are much more than mere specks of carbon; they are whispering promises of ultra-secure communications, enhanced computing power, and cutting-edge sensing capabilities. However, to reach the zenith of their potential, it is essential to create nanodiamonds that are not only uniform in size but also equipped with single quantum emitters. Now, in a landmark study published on May 6, 2019, in Scientific Reports, with DOI 10.1038/s41598-019-43304-5, researchers from the Department of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology, joined by experts from the Center for Functional Nanomaterials at Brookhaven National Laboratory and the Department of Materials Science and Engineering at The University of Texas at Dallas, have unveiled a trailblazing method that paves the way for this innovation.
The study, which involves technology funded by the U.S. Department of Energy under grants DE-SC0012704, presents an advanced top-down fabrication process that deftly employs self-assembled block copolymer masks in conjunction with directional and isotropic reactive ion etching to yield prodigiously uniform nanodiamonds boasting a precise average size of 30.0 ± 5.4 nm. Lead author Zheng Jiabao and colleagues demonstrate the successful detection of emission from singularly bright nitrogen vacancy centers nestled within these fabricated nanodiamonds. Furthermore, the scalability of this method heralds a transformative leap for quantum applications, as it permits lithographically precise patterning over expansive areas of diamond substrates, followed by meticulous release into nanodiamonds of uniform size.
Scientific Context and Implications
Nanodiamonds—when hosting color centers such as nitrogen vacancies—act as stable quantum bits (qubits), capable of operating at room temperature, a much-coveted property for practical quantum computing. The pursuit of a reliable and consistent fabrication process for nanoscale diamonds featuring these color centers has been fraught with challenges. The homogeneity of size and avoidance of aggregation are critical to ensuring that the optical and electronic properties of the nanodiamonds are uniformly replicable, scaling from single units to an array of quantum applications.
The fabrication process presented in the Scientific Reports article effectively addresses these pressing challenges by marrying the precision inherent in block copolymer self-assembly with the versatility of reactive ion etching techniques. The result is a high-throughput method capable of producing nanodiamonds with tight size distributions and single quantum emitters, which is a boon for applications such as quantum cryptography, where the secure transmission of information is encoded within the quantum states of photons emitted by these emitters.
The practical implications of the researchers’ work extend into the realm of biomedical sciences as well. Nanodiamonds have been shown to possess unique biocompatible properties making them suitable for use in drug delivery systems, bio-imaging, and even fluorescent trackers within living organisms without invoking toxicity. The uniformity and control afforded by the new fabrication process stimulate potential advancements in these biomedical applications, ushering in new opportunities in personalized medicine and diagnostics.
Technical Innovation
At the heart of this breakthrough lies the ingenuity of block copolymer self-assembly. In essence, block copolymers are composed of two or more distinct polymer blocks, which can autonomously organize into structured nanoscale patterns. By carefully selecting block copolymers with compatible properties and employing calculated etching techniques, the researchers were able to achieve highly uniform patterns that served as masks for the etching of the diamond substrates. This precise control over the mask geometry translated directly into the resulting nanodiamond dimensions.
What sets this method apart is not just the homogeneity of the produced nanodiamonds, but also the integration of nitrogen vacancy centers—imperfections within the diamond lattice that can trap electrons. The presence of these centers is crucial for quantum applications, as they allow for the reliable storage and manipulation of quantum information. The method’s ability to incorporate these centers systematically, and with a high degree of spatial control, marks a vibrant leap forward in the journey to make quantum technology widely accessible and functional.
Advances Beyond Previous Work
Prior to this development, nanodiamond production mainly relied on random fragmentation techniques, which resulted in varying particle sizes and a broad emission spectrum from color centers. Moreover, isolating single quantum emitters proved challenging due to these inconsistencies. The innovative method introduced by Jiabao and the team ensures that each nanodiamond can act as a high-quality qubit or sensor with predictable and reproducible quantum behavior.
Conclusion and Future Outlook
The successful fabrication procedure outlined in the Scientific Reports paper breaks new ground in the world of quantum technology. By mastering the top-down approach to create uniform, non-aggregated nanodiamonds with integrated single quantum emitters, the researchers offer a potent tool that can be leveraged across a range of quantum systems. The foreseeable future holds a landscape where these nanodiamonds could be integral components in the burgeoning quantum industry, elevating communication security, computational prowess, and sensing precision to unprecedented heights.
Looking ahead, new research can build on this framework to explore the integration of other color centers, such as silicon vacancies or germanium vacancies, that operate at distinct wavelengths, thereby expanding the palette of quantum functionality. Furthermore, as this method garners adoption, we can anticipate a wave of innovations in fabricating quantum devices and exploring nanodiamond-hosted quantum phenomena.
References
1. DOI: 10.1038/s41598-019-43304-5
2. Pingault B et al. Nat. Commun. 2017;8:15579. doi: 10.1038/ncomms15579.
3. Lienhard B et al. Optica, OPTICA. 2016;3:768–774. doi: 10.1364/OPTICA.3.000768.
4. Atatüre M et al. Nature Reviews Materials. 2018;3:38–51. doi: 10.1038/s41578-018-0008-9.
5. Degen CL et al. Rev. Mod. Phys. 2017;89:035002. doi: 10.1103/RevModPhys.89.035002.
Keywords
1. Nanodiamond fabrication
2. Uniform nanodiamonds
3. Quantum emitters in diamonds
4. Nitrogen vacancy centers
5. Quantum technology advancements