Cavity QED of Spins in Diamond via Dark States

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Nontechnical Abstract:In a quantum communications network, information can be encoded on light pulses containing single photons. This quantum information can propagate between individual nodes containing single atoms, including artificial atoms. The transfer of quantum information between single photons and single atoms in the network can be exploited to implement secure communication and to solve computational problems that would otherwise be difficult with conventional computers. This experimental project aims to demonstrate this transfer process by developing and using an experimental platform, in which special defect centers in an otherwise perfect diamond crystal are used as artificial atoms. Single defect centers are coupled to light pulses that are confined in dimensions less than 50 micrometers. This spatial confinement greatly increases the light intensity that can be generated by a single photon and thus enhances its coupling to the defect center. A specific goal is to transfer quantum information from one defect center to another via this enhanced coupling to single photons. Research activities of this project also provide excellent training opportunities for graduate and undergraduate students in areas including nanophotonics and nanofabrication as well as quantum science and technology. This training prepares the students for careers in academia, industry, or government. Technical Abstract:This project focuses on controlling optical interactions of a single spin at the level of single cavity photons via a dark state, which can mediate reversible state transfers between spins and photons, while circumventing decoherence processes such as spontaneous emission. The project develops and explores a composite cavity quantum electrodynamics (QED) system, in which negatively charged silicon vacancy (SiV) centers in a 100 nm thick diamond membrane couple to evanescent fields of optical whispering gallery modes in a silica microresonator. The composite system can enable spin-state selective coupling to the cavity mode as well as the realization of the good cavity limit, in which the cavity linewidth is small compared with the single-photon dipole coupling rate. Electromagnetically induced transparency will be used to probe and characterize the dark state of the composite cavity QED system. The dark state will then be exploited for reversible state transfers between spins and photons, studies of higher energy ladder states of the cavity QED system, and cavity-mediated coherent interactions between two SiV spins.This Division of Materials Research (DMR) grant supports research to understand composite cavity quantum electrodynamics (QED) systems with funding from the Condensed Matter Physics (CMP) program in DMR, the Atomic, Molecular, and Optics (AMO) program in the Division of Physics (PHY), and the Office of Multidisciplinary Activities (OMA) of the Mathematical and Physical Sciences Directorate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.