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The silicon vacancy centers in SiC: determination of intrinsic spin dynamics for integrated quantum photonics

Di Liu, Florian Kaiser, Vladislav Bushmakin, Erik Hesselmeier, Timo Steidl, Takeshi Ohshima, Nguyên Tiên Són, Jawad Ul‐Hassan, Öney O. Soykal, Jörg Wrachtrup

Published Jul 23, 2024• 31 citations
Publisher

Abstract

Abstract The negatively charged silicon vacancy center ( $${{\rm{V}}}_{{\rm{Si}}}^{-}$$ V Si − ) in silicon carbide (SiC) is an emerging color center for quantum technology covering quantum sensing, communication, and computing. Yet, limited information currently available on the internal spin-optical dynamics of these color centers prevents us from achieving the optimal operation conditions and reaching the maximum performance especially when integrated within quantum photonics. Here, we establish all the relevant intrinsic spin dynamics of the $${{\rm{V}}}_{{\rm{Si}}}^{-}$$ V Si − center at cubic lattice site (V2) in 4H-SiC by an in-depth electronic fine structure modeling including the intersystem-crossing and deshelving mechanisms. With carefully designed spin-dependent measurements, we obtain all the previously unknown spin-selective radiative and non-radiative decay rates. To showcase the relevance of our work for integrated quantum photonics, we use the obtained rates to propose a realistic implementation of time-bin entangled multi-photon GHZ and cluster state generation. We find that up to three-photon GHZ or cluster states are readily within reach using the existing nanophotonic cavity technology.

DOI
10.1038/s41534-024-00861-6

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Robust single spin color centers in solid state systems with telecom wavelength emission are vital to quantum photonics and quantum networks. The nitrogen vacancy (NV) centers in silicon carbide (SiC) have become promising platforms for those applications. However, little is known about the detailed optical properties of the NV centers. In this paper, we investigate the photophysics of the single NV centers in 4H-SiC. The results demonstrate that the NV centers comprise three energy-level electronic structures. Particularly, for c -axis NV centers, both the excitation and the emission polarization degrees are larger than 90%. Photon purity and photostability of the single NV centers are maintained at an elevated temperature up to 400 K. These experiments constitute an important step toward using the NV centers in SiC with respect to quantum photonics.

ACS Photonics•Jun 19, 2020•46 citations
Abstract The negatively charged silicon vacancy center ( VSi−{{\rm{V}}}_{{\rm{Si}}}^{-}VSi−​ V Si − ) in silicon carbide (SiC) is an emerging color center for quantum technology covering quantum sensing, communication, and computing. Yet, limited information currently available on the internal spin-optical dynamics of these color centers prevents us from achieving the optimal operation conditions and reaching the maximum performance especially when integrated within quantum photonics. Here, we establish all the relevant intrinsic spin dynamics of the VSi−{{\rm{V}}}_{{\rm{Si}}}^{-}VSi−​ V Si − center at cubic lattice site (V2) in 4H-SiC by an in-depth electronic fine structure modeling including the intersystem-crossing and deshelving mechanisms. With carefully designed spin-dependent measurements, we obtain all the previously unknown spin-selective radiative and non-radiative decay rates. To showcase the relevance of our work for integrated quantum photonics, we use the obtained rates to propose a realistic implementation of time-bin entangled multi-photon GHZ and cluster state generation. We find that up to three-photon GHZ or cluster states are readily within reach using the existing nanophotonic cavity technology.
The negatively-charged silicon vacancy center (VSi−\rm V_{Si}^-VSi−​) in silicon carbide (SiC) is an emerging color center for quantum technology covering quantum sensing, communication, and computing. Yet, limited information currently available on the internal spin-optical dynamics of these color centers prevents us achieving the optimal operation conditions and reaching the maximum performance especially when integrated within quantum photonics. Here, we establish all the relevant intrinsic spin dynamics of negatively charged VSi−\rm V_{Si}^-VSi−​ center in 4H-SiC by an in-depth electronic fine structure modeling including intersystem-crossing and deshelving mechanisms. With carefully designed spin-dependent measurements, we obtain all previously unknown spin-selective radiative and non-radiative decay rates. To showcase the relevance of our work for integrated quantum photonics, we use the obtained rates to propose a realistic implementation of time-bin entangled multi-photon GHZ and cluster state generation. We find that up to 3-photon GHZ/cluster states are readily within reach using the existing nanophotonic cavity technology.
Color centers in silicon carbide are emerging candidates for distributed spin-based quantum applications due to the scalability of host materials and the demonstration of integration into nanophotonic resonators. Recently, silicon vacancy centers in silicon carbide have been identified as a promising system with excellent spin and optical properties. Here, we fully study the spin-optical dynamics of the single silicon vacancy center at hexagonal lattice sites, namely V1, in 4H-polytype silicon carbide. By utilizing resonant and above-resonant sublifetime pulsed excitation, we determine spin-dependent excited-state lifetimes and intersystem-crossing rates. Our approach to inferring the intersystem-crossing rates is based on all-optical pulsed initialization and readout scheme, and is applicable to spin-active color centers with similar dynamics models. In addition, the optical transition dipole strength and the quantum efficiency of V1 defect are evaluated based on coherent optical Rabi measurement and local-field calibration employing electric field simulation. The measured rates well explain the results of spin-state polarization dynamics, and we further discuss the altered photoemission dynamics in resonant enhancement structures such as radiative lifetime shortening and Purcell enhancement. By providing a thorough description of the V1 center's spin-optical dynamics, our work provides deep understanding of the system, which guides implementations of scalable quantum applications based on silicon vacancy centers in silicon carbide.
We highlight our work [1] on nanophotonic integration of color centers in semiconductor silicon carbide (SiC). We show ion-assisted implantation and waveguide-integration of silicon vacancy centers (VSi) in 4H-SiC with nearly lifetime limited optical lines and record spin coherence times. We further show controlled coupling to nearby nuclear spin qubits. Our experiments can be performed at high temperatures (T=20 K), thus enabling fast and direct nuclear spin control. Our work shows that VSi centers in SiC are attractive for developing next-generation quantum (computational) networks based on optically interconnected spin-based qubit clusters. [1] Babin et al, Nature Materials, to appear (2021)
The identification of a microscopic configuration of point defects acting as quantum bits is a key step in the advance of quantum information processing and sensing. Among the numerous candidates, silicon-vacancy related centers in silicon carbide (SiC) have shown remarkable properties owing to their particular spin-3/2 ground and excited states. Although, these centers were observed decades ago, two competing models, the isolated negatively charged silicon vacancy and the complex of negatively charged silicon vacancy and neutral carbon vacancy [Phys. Rev. Lett. 115, 247602 (2015)], are still argued as an origin. By means of high-precision first-principles calculations and high-resolution electron spin resonance measurements, we here unambiguously identify the Si-vacancy related qubits in hexagonal SiC as isolated negatively charged silicon vacancies. Moreover, we identify the Si-vacancy qubit configurations that provide room-temperature optical readout.
In the past decade, color centers in silicon carbide (SiC) have emerged as promising platforms for various quantum information technologies. There are three main types of color centers in SiC: silicon-vacancy centers, divacancy centers, and nitrogen-vacancy centers. Their spin states can be polarized by laser and controlled by microwave. These spin defects have been applied in quantum photonics, quantum information processing, quantum networks, and quantum sensing. In this review, we first provide a brief overview of the progress in single-color center fabrications for the three types of spin defects, which form the foundation of color center-based quantum technology. We then discuss the achievements in various quantum sensing, such as magnetic field, electric field, temperature, strain, and pressure. Finally, we summarize the current state of fabrications and quantum sensing of spin defects in SiC and provide an outlook for future developments.
Robust single spin color centers in solid state systems with telecom wavelength emission are vital to quantum photonics and quantum networks. The nitrogen vacancy (NV) centers in silicon carbide (SiC) have become promising platforms for those applications. However, little is known about the detailed optical properties of the NV centers. In this paper, we investigate the photophysics of the single NV centers in 4H-SiC. The results demonstrate that the NV centers comprise three energy-level electronic structures. Particularly, for c -axis NV centers, both the excitation and the emission polarization degrees are larger than 90%. Photon purity and photostability of the single NV centers are maintained at an elevated temperature up to 400 K. These experiments constitute an important step toward using the NV centers in SiC with respect to quantum photonics.