This program explores quantum control at the level of single photon, single electron spin, and single nuclear spin in a unique system that features strong coherent coupling between a photon and an electron spin and between an electron spin and a nearby nuclear spin. The experimental studies will be carried out in a cavity QED system, in which a negatively charged nitrogen vacancy (NV) center in a diamond nanopillar couples strongly to a whispering gallery mode (WGM) in a silica microresonator. Proposed research involves close collaborations between the groups at the University of Oregon and the University of Pittsburg, and builds upon recent advances of these two groups in developing a cavity QED system for NV centers and in realizing quantum control of individual electron and nuclear spins, especially quantum state mapping between an electron spin in a NV center and a proximal carbon-13 nuclear spin in the diamond lattice. The primary technical challenges of the proposed research are anticipated to be the development of a well-controlled strong-coupling cavity QED system, the exquisite control of NV excited-state level structures in a nanopillar for dark-state adiabatic evolution, and the efficient readout of electron and nuclear spins.
Broader Impact: Combining quantum control of individual photons, electron spins, and nuclear spins in a solid-state system develops new technical capabilities, creates new model systems, and opens up new possibilities for the emerging field of quantum information science. A light-matter interface with electron and nuclear spins can enable a robust quantum memory for single photons and can also significantly advance our ability to control the coherent coupling between distant and well-isolated nuclear spins. The entanglement of distant nuclear spins or distant electron-nuclear spin pairs in a solid-state environment provides the scientific community an excellent model system to explore fundamental issues of quantum entanglement and error correction. These issues are central to the field of quantum information as well as to our understanding of the quantum world. With a solid-state light-matter interface and with long-lived quantum memory, it might be possible to explore complex quantum networks that can distribute and transport quantum information between distant quantum nodes. The research program also makes important contributions to education and human resource by providing training for graduate and undergraduate students in areas of both scientific and technological importance. This training will prepare the students for careers in academia, industry, and government.
This experimental program at the University of Oregon aims to explore the physics and develop the technology that can be used in a quantum communication network, an internet that exploits exotic quantum properties such as quantum coherent superposition and quantum entanglement. The research program has focused on the development of a model system that enables the coherent interaction between a single photon and a single electron spin in diamond. This model system can serve as an interconnect in a quantum internet, converting quantum states between spins and photons. The achievements of this program include the realization of an experimental platform for such a model system and the demonstration of using laser pulses to control the quantum states of electron spins, a crucial step for the operation of such coupled spin-photon systems. Electron spins in a solid such as diamond have shown great promise as qubits for quantum information processing. These spin systems, however, are also subject to flip flops of the surrounding nuclear spins, shortening the lifetime of the spin coherence and thus interrupting the coherent spin-photon interactions. In general, decoherence of a quantum state due to uncontrolled interactions with its environment puts a fundamental limit on applications of quantum technologies. This program has realized a new approach for protecting an electron spin from environment-induced decoherence. This technique applies continuous radiation fields to a quantum system, dressing a spin with microwave fields. The resulting hybrid spin-field states, called "dressed states," can be incredibly insensitive to the system’s noisy magnetic environment. This research program has also made important contributions to education and human resource by providing training for graduate and undergraduate students in areas of both scientific and technological importance. Two students supported by this program have received their physics PhD degrees.
