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arXiv:2112.10211 · Physical Review Research

Multi-photon multi-quantum transitions in the spin- 3 2 silicon-vacancy centers of SiC

Harpreet Singh, Mario Alex Hollberg, Andrey N. Anisimov, P. G. Baranov, Dieter Suter

Published Apr 8, 2022• 12 citations
arXivHTMLPDF

Abstract

Silicon vacancy centers in silicon carbide are promising candidates for storing and manipulating quantum information. Implementation of fast quantum gates is an essential requirement for quantum information processing. In a low magnetic field, the resonance frequencies of silicon vacancy spins are in the range of a few MHz, the same order of magnitude as the Rabi frequencies of typical control fields. As a consequence, the rotating wave approximation becomes invalid and nonlinear processes like the absorption and emission of multiple photons become relevant. This paper focuses on multi-photon transitions of negatively charged silicon vacancies driven by a strong RF field. We present continuous-wave optically detected magnetic resonance (ODMR) spectra measured at different RF powers to identify the 1-, 2-, and 3 RF photon transitions of different types of the silicon vacancy in the $6H$-SIC polytype. Time-resolved experiments of Rabi oscillations and free induction decays of these multiple RF photon transitions were observed. Apart from zero-field data, we also present spectra in magnetic fields with different strength and orientation with respect to the system's symmetry axis.

DOI
10.1103/physrevresearch.4.023022

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Silicon vacancy centers in silicon carbide are promising candidates for storing and manipulating quantum information. Implementation of fast quantum gates is an essential requirement for quantum information processing. In a low magnetic field, the resonance frequencies of silicon vacancy spins are in the range of a few MHz, the same order of magnitude as the Rabi frequencies of typical control fields. As a consequence, the rotating wave approximation becomes invalid and nonlinear processes like the absorption and emission of multiple photons become relevant. This paper focuses on multi-photon transitions of negatively charged silicon vacancies driven by a strong RF field. We present continuous-wave optically detected magnetic resonance (ODMR) spectra measured at different RF powers to identify the 1-, 2-, and 3 RF photon transitions of different types of the silicon vacancy in the 6H6H6H-SIC polytype. Time-resolved experiments of Rabi oscillations and free induction decays of these multiple RF photon transitions were observed. Apart from zero-field data, we also present spectra in magnetic fields with different strength and orientation with respect to the system's symmetry axis.
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.
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.
Abstract Multiple-microwave-photon transition is a nonlinear process involving the simultaneous absorption of multiple microwave photons to reach a higher energy state. This phenomenon enables microwave frequency conversion, a crucial technique for spin-wave devices, frequency synthesizers and communication devices. However, it has not been observed in nitrogen-vacancy (NV) centers in diamonds, which serve as a key quantum platform linking flying qubits, microwave photons, and solid-state spins. In this work, we first observed multiple-microwave-photon transitions in NV centers in diamonds, using optically detected magnetic resonance (ODMR) methods with a single laser and microwave beam. We demonstrate that microwave frequencies, effective g-factor, and angular momentum exhibit a 1/n scaling law, but the linewidth exhibits a 1/n^2 scaling law for n-photon transitions between the ground states. Additionally, we detect the hyperfine structure of the ground states and achieve coherent spin manipulation under multi-photon excitation. Our findings offer a novel approach for the precise manipulation of NV center spin states, advancing quantum sensing and quantum information.
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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.
Realization of quantum memory with a photonic interface in the telecommunication bands in a wafer-scalable platform is a central requirement for long-distance quantum networks. Silicon carbide (SiC) provides a technologically mature host for integrated quantum photonics, yet only a limited number of defects combine spin functionality with telecom emission. Here we report on chlorine-based defects in 4H-SiC as a platform for telecom-band quantum memory. The emission of these defects spans the entire telecommunication range with zero-phonon lines in the O- and C-bands and a Debye-Waller factor of up to 39 %39 \, \%39%. Time-resolved photoluminescence measurements reveal a short excited-state lifetime in the sub-nanosecond range. We demonstrate that these defects are spin-active even at room temperature, exhibiting optically detected magnetic resonances (ODMR) in the sub-GHz frequency range. Using ODMR spectroscopy and Ramsey interferometry, we resolve the hyperfine structure arising from the interaction with 35Cl^{35}\mathrm{Cl}35Cl nuclear spins. The ODMR spectra exhibit complex behaviour in an external magnetic field due to mixing of electron-nuclear spin states, which is well reproduced by our simulations. The spin relaxation and coherence times are in the sub-microsecond range, limited by rapid quenching of the ODMR contrast and attributed to charge-state metastability. The combination of telecom-band emission, coherent spin control and compatibility with wafer-scale fabrication positions Cl-related defects in SiC as a promising platform for chip-scale quantum memories with spin-photon interfaces operating in the fiber-optic telecommunication windows.