- Electrical Engineering and Computer Science
Top 3 Areas of Expertise:
Quantum bits with long coherence times at room temperature will enable breakthroughs in the fields of quantum computation, communication and sensing. Currently, the most promising candidate for a room-temperature system is the nitrogen-vacancy (NV) defect center in diamond. My research area involves understanding the physics of the NV center specifically in the context of nanophotonics. I primarily work with nanometer-sized diamonds, and more specifically, focus on utilizing the spin properties in a nitrogen-vacancy defect (~50ppm) for applications such as magnetic sensors in biological and electronic systems, and as building blocks for scalable quantum communication systems.
During my graduate career, I have worked exclusively with NVs in diamond, which is effectively a trapped ion in the solid-state. The primary appeal of NVs is that the solid-state environment allows for fabrication of nanophotonic devices for enhancing light-matter interaction. This direction led to a recent publication for which I was an equally contributing first-author (“Coherent spin control of a nanocavity-enhanced qubit in diamond.” Nature Comm. 2015). In this paper, I demonstrated with my colleagues a Purcell enhancement of ~60 on a single NV, and coherent control of the NV spin out to 200 us. The next steps for this project are to make such cavity-enhanced NVs directly on integrated photonic devices containing beam splitters, along with high-efficiency superconducting detectors. This would constitute a full logical qubit with NVs, which is then potentially useful as a quantum repeater, or a one-way quantum computer.
In addition to having experience with nano-fabrication, cryogenic measurements, and coherent spin manipulation of NVs in nanophotonic structures, I have also followed in the footsteps of previous ion-trappers in developing a super-resolution imaging technique for NVs (Nano Letters, 2013), and implemented grating devices for drastically increasing the photon collection efficiencies from single NVs (Nano Letters, 2015).
I have also spent time outside of my own research managing several undergraduate and younger graduate research students, as well as being a co-organizer with fellow graduate students for a weekly seminar series for the NSF-sponsored Interdisciplinary Quantum Information for Science and Engineering (iQuISE) community on campus. Ultimately, I very much enjoy a highly collaborative environment, and expect the field of quantum information processing to catalyze transformations for many fields of science.
I believe a lot of my experience with coherent control on NVs in nanophotonic structures can be readily translated into other quantum information technologies, especially since the FDTD simulations, electronic design, and optical characterization all share commonalities. I am anticipating a graduation date of September 2016, and would be interested in a full-time postdoctoral or research position by October/November of 2016. I look forward to hearing from you soon either by phone (626-872-5342) or by e-mail.
Expected date of graduation:
The exceptional optical and spin properties of the negatively charged nitrogen-vacancy (NV−) center in diamond have led to a wide range of hallmark demonstrations ranging from super-resolution imaging to quantum entanglement, teleportation, and sensing. The solid-state environment of the NV− allows for engineering nanostructures that can further enhance the properties of the NV−. Towards demonstrating the individual components needed for a diamond-based quantum network, we recently achieved coherent electron spin control of long-lived NV−s in diamond nanostructures using a transferrable hard-mask for both etching and ion implantation. We also developed a super-resolution imaging technique for characterizing such systems. However, it remains an open question whether traditional nano-fabrication processes for patterning nanostructures into diamond would cause irrecoverable damage or introduce atomic impurities to the crystal that would lead to a significant degradation of the NV− properties. Furthermore, one of the remaining challenges is to allow for fault tolerance by creating multiple, magnetically-coupled NV−s within each nanostructured device for improved robustness and scalability as a reliable node within a quantum network. To address this scalability issue, the next major step of my research effort will be to experimentally demonstrate high fidelity quantum state preparation of NV quantum registers. It may then be possible to design nanostructures for achieving higher fidelity initialization and gate operations on multi-spin registers of NV−s within nanostructures.
Top 5 Awards and honors (name of award, date received):
5 Recent Papers:
L. Li*, T. Schröder*, E. H. Chen*, M. Walsh, I. Bayn, I. Goldstein, O. Gaathon, M. E. Trusheim, M. Lu, J. Mower, and others, “Coherent spin control of a nanocavity-enhanced qubit in diamond,” Nature Communications, vol. 6, 2015.
*equally contributing authors
L. Li*, E. H. Chen*, J. Zheng, S. L. Mouradian, F. Dolde, T. Schröder, S. Karaveli, M. L. Markham, D. J. Twitchen, and D. Englund, “Efficient Photon Collection from a Nitrogen Vacancy Center in a Circular Bullseye Grating,” Nano Lett., vol. 15, no. 3, pp. 1493–1497, Mar. 2015.
*equally contributing authors
S. I. Knysh, E. H. Chen, and G. A. Durkin, “True Limits to Precision via Unique Quantum Probe,” arXiv:1402.0495 [math-ph, physics:quant-ph], Feb. 2014.
E. H. Chen, O. Gaathon, M. E. Trusheim, and D. Englund, “Wide-field multispectral super-resolution imaging using spin-dependent fluorescence in nanodiamonds,” Nano Letters, pp. 1–13, 2013.
R. Barnett, E. Chen, and G. Refael, “Vortex synchronization in Bose–Einstein condensates: a time-dependent Gross–Pitaevskii equation approach,” New Journal of Physics, vol. 12, no. 4, p. 043004, 2010.