Mechanically-Mediated Spin Entanglement in Diamond

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Fundamental aspects of quantum mechanics, such as the superposition and entanglement of quantum states, can, in principle, be exploited to solve computational problems that are impractical or impossible to solve with conventional, classical computers. Realizing this goal remains technically challenging, however, because these quantum traits are delicate and sensitive to noise and interactions with the environment, therefore requiring precise control of the interactions between the individual qubits which store quantum information. This project will attempt to use acoustic waves in a nano-mechanical resonator to mediate interactions between two qubits in a solid-state system. Acoustic waves propagate much more slowly than light, and they cannot propagate in a vacuum. As a result, acoustic waves can be conveniently confined and guided in a solid. In this way, these mechanical waves offer advantages over photonics-based platforms by enabling on-chip communication between qubits. The near-term goal of this program is to generate quantum entanglement between two qubits via mechanically-mediated interactions. The long-term goal is to develop a mechanics-based platform for implementation of a solid-state quantum computer. This project will promote education and human resources by providing excellent training to graduate and undergraduate students in areas of both scientific and technological importance. This project aims to demonstrate mechanically-mediated spin entanglement in a spin-mechanical system, establishing a mechanics-based solid-state platform for quantum computing. The research efforts will be carried out with a diamond nanomechanical resonator in which two electron spins couple to a common mechanical mode. This experimental platform exploits the strong excited-state strain coupling of nitrogen vacancy (NV) centers for spin-mechanical coupling, but circumvents decoherence of the excited states through optically-controlled adiabatic evolution of the ground spin states. Coherent coupling between a single NV center and a single phonon will be investigated. This will be followed by the study of coherent coupling between two NV centers through the exchange of single phonons. The successful implementation of these efforts should then enable the pursuit of mechanically-mediated entanglement between two NV centers. The Sorensen-Molmer entanglement scheme, which is relatively robust against thermal mechanical motion, will be used for the generation of a maximally-entangled spin state.