The silicon-vacancy ($mathrm{SiV}^-$) color center in diamond has attracted attention due to its unique optical properties. It exhibits spectral stability and indistinguishability that facilitate efficient generation of photons capable of demonstrati
ng quantum interference. Here we show high fidelity optical initialization and readout of electronic spin in a single $mathrm{SiV}^-$ center with a spin relaxation time of $T_1=2.4pm0.2$ ms. Coherent population trapping (CPT) is used to demonstrate coherent preparation of dark superposition states with a spin coherence time of $T_2^star=35pm3$ ns. This is fundamentally limited by orbital relaxation, and an understanding of this process opens the way to extend coherences by engineering interactions with phonons. These results establish the $mathrm{SiV}^-$ center as a solid-state spin-photon interface.
The characteristic transition of the NV- centre at 637 nm is between ${}^3mathrm{A}_2$ and ${}^3mathrm{E}$ triplet states. There are also intermediate ${}^1mathrm{A}_1$ and ${}^1mathrm{E}$ singlet states, and the infrared transition at 1042 nm betwee
n these singlets is studied here using uniaxial stress. The stress shift and splitting parameters are determined, and the physical interaction giving rise to the parameters is considered within the accepted electronic model of the centre. It is established that this interaction for the infrared transition is due to a modification of electron-electron Coulomb repulsion interaction. This is in contrast to the visible 637 nm transition where shifts and splittings arise from modification to the one-electron Coulomb interaction. It is also established that a dynamic Jahn-Teller interaction is associated with the singlet ${}^1mathrm{E}$ state, which gives rise to a vibronic level 115 $mathrm{cm}^{-1}$ above the ${}^1mathrm{E}$ electronic state. Arguments associated with this level are used to provide experimental confirmation that the ${}^1mathrm{A}_1$ is the upper singlet level and ${}^1mathrm{E}$ is the lower singlet level.
We demonstrate that silicon-vacancy (SiV) centers in diamond can be used to efficiently generate coherent optical photons with excellent spectral properties. We show that these features are due to the inversion symmetry associated with SiV centers, a
nd demonstrate generation of indistinguishable single photons from separate emitters in a Hong-Ou-Mandel (HOM) interference experiment.Prospects for realizing efficient quantum network nodes using SiV centers are discussed.
Emitters of indistinguishable single photons are crucial for the growing field of quantum technologies. To realize scalability and increase the complexity of quantum optics technologies, multiple independent yet identical single photon emitters are a
lso required. However typical solid-state single photon sources are inherently dissimilar, necessitating the use of electrical feedback or optical cavities to improve spectral overlap between distinct emitters. Here, we demonstrate bright silicon-vacancy (SiV-) centres in low-strain bulk diamond which intrinsically show spectral overlap of up to 91% and near transform-limited excitation linewidths. Our results have impact upon the application of single photon sources for quantum optics and cryptography, and the production of next generation fluorophores for bio-imaging.
The negatively-charged silicon-vacancy (SiV$^-$) center in diamond is a promising single photon source for quantum communications and information processing. However, the centers implementation in such quantum technologies is hindered by contention s
urrounding its fundamental properties. Here we present optical polarization measurements of single centers in bulk diamond that resolve this state of contention and establish that the center has a $langle111rangle$ aligned split-vacancy structure with $D_{3d}$ symmetry. Furthermore, we identify an additional electronic level and evidence for the presence of dynamic Jahn-Teller effects in the centers 738 nm optical resonance.
