Quantum Spin-Phonon Networks with Silicon-Vacancy Centers in Diamond

• Applicant: Dr. Viviana Villafane
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544483723

A spin-photon interface (SPI) is a physical system that allows to link single spins and photons, thus entangling stationary and flying qubits. They facilitate high-fidelity transfer of quantum states between distant locations throughout a quantum network, underpinning the implementation of distributed quantum computing and secure quantum communications. Negatively charged silicon vacancies in diamond (SiVs-) have recently emerged as a leading SPI because they allow optically mediated entanglement of individually controllable spins with additional access to several long-lived nuclear carbon spins in their surroundings. However, the internal level structure of the SiV- is perfectly suited to generate spin-phonon entanglement: Due to a strong spin orbit coupling, SiV- feature a two-fold orbitally split and spin degenerate ground state separated by an energy of 50GHz. In this context, the aim of this research proposal is to establish a novel “spin-photon-phonon interface” using SiVs- in diamond and 50GHz-coherent acoustic phonons. We have designed a 0D optomechanical structure containing single SiV- spins coupled to a high-quality factor acousto-optical cavity, simultaneously resonant to the SiV- optical transitions and a 50GHz mechanical mode. The strong acousto-optical coupling in these structures will be exploited to perform spin initialization techniques in SiVs- while optically cooling the host diamond lattice. Thereby, the phonon population at ~50GHz will be decreased and spin dephasing via single phonon absorption will be readily suppressed at ~4K, suppresing the need to use complex dilution refrigerators operated at ~mK temperatures. Moreover, by performing high-frequency coherent acoustic drive of the SiV-, we will relax the microwave driving selection rules inherent to SiVs- in diamond. Since our devices operate in the strong coupling regime, they will sustain high-fidelity quantum state transfer between the SiV- spin qubit and single 50GHz acoustic phonons, via Jaynes-Cummings type of interactions. Ultimately, we will facilitate the transduction between spins and phonons and obtain unprecedented access to the quantum properties of these coupled systems. Our project will unravel physical regimes in which light, spin qubits and phonons are coupled at the single particle level and interconnected in a solid-state platform.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Tunable ps laser system
• Instrumentation Group: 5700 Festkörper-Laser