Solid-state quantum emitters that couple coherent optical transitions to long-lived spin states are essential for quantum networks. Here we report on the spin and optical properties of single tin-vacancy (SnV) centers in diamond nanostructures. Through magneto-optical spectroscopy at 4 K, we verify the inversion-symmetric electronic structure of the SnV, identify spin-conserving and spin-flipping transitions, characterize transition linewidths, and measure electron spin lifetimes. We find that the optical transitions are consistent with the radiative lifetime limit and that the spin lifetimes are longer than for other inversion-symmetric color centers under similar conditions. These properties indicate that the SnV is a promising candidate for quantum optics and quantum networking applications.A central goal of quantum information processing is the development of quantum networks consisting of stationary, long-lived matter qubits coupled to flying photonic qubits [1,2], with applications in quantum computing, provably secure cryptography, and quantumenhanced metrology [3]. Among matter qubits, quantum emitters in wide-bandgap semiconductors [4,5] have emerged as leading systems as their coherent, spinselective optical transitions act as an interface between quantum information stored in their spin degrees of freedom and emitted photons. While most work has so far focused on the nitrogen-vacancy (NV) center in diamond [6-8], its relatively poor optical properties, including a low percentage of emission into the coherent zero-phonon-line (ZPL) [9] and large spectral diffusion when located near surfaces [10,11], have fueled the investigation of alternative emitters. These include the group-IV color centers in diamond [12], comprising the silicon-vacancy (SiV) [13][14][15][16], germanium-vacancy (GeV) [17,18], and the recently observed lead-vacancy (PbV) [19] centers. These centers have a large fraction of emission into the ZPL and a crystallographic inversion symmetry that limits spectral diffusion and inhomogeneous broadening [20,21]. Unlike the NV center, however, the electronic spin coherence of SiV and GeV centers is limited by phonon scattering to an upperlying ground-state orbital [22,23], requiring operation at dilution-refrigerator temperatures (∼ 100 mK) [24,25], or controllably induced strain [26] to achieve long coherence times.The tin-vacancy (SnV) center in diamond [27, 28] is a group-IV color center that promises favorable optical properties and long spin coherence time at readily achievable temperatures (liquid helium, ∼ 4 K). DFT calculations predict that the SnV has the same symmetry as the SiV and GeV[9], while experimental measurement of a large ground-state orbital splitting indicates that single-phonon scattering, the dominant spin dephasing mechanism of SiV and GeV centers at liquid helium temperatures, should be suppressed significantly [27]. In this work, we report spectroscopic measurements that are consistent with the conjectured electronic structure of the SnV, demonstrate that its optical...

We report on quantum emission from Pb-related color centers in diamond following ion implantation and high temperature vacuum annealing. First-principles calculations predict a negatively-charged Pb-vacancy center in a split-vacancy configuration, with a zero-phonon transition around 2.3 eV. Cryogenic photoluminescence measurements performed on emitters in nanofabricated pillars reveal several transitions, including a prominent doublet near 520 nm. The splitting of this doublet, 2 THz, exceeds that reported for other group-IV centers. These observations are consistent with the PbV center, which is expected to have the combination of narrow optical transitions and stable spin states, making it a promising system for quantum network nodes.

No abstract

Abstract:Towards building large-scale integrated photonic systems for quantum information processing, spatial and spectral alignment of single quantum systems to photonic nanocavities is required. Here, we demonstrate spatially targeted implantation of nitrogen vacancy (NV) centers into the mode maximum of 2-d diamond photonic crystal cavities with quality factors up to 8000, achieving an average of 1.1 ± 0.2 NVs per cavity. Nearly all NV-cavity systems have significant emission intensity enhancement, reaching a cavity-fed spectrally selective intensity enhancement, F int , of up to 93. Although spatial NV-cavity overlap is nearly guaranteed within about 40 nm, spectral tuning of the NV's zero-phonon-line (ZPL) is still necessary after fabrication. To demonstrate spectral control, we temperature tune a cavity into an NV ZPL, yielding F Z PL int ∼ 5 at cryogenic temperatures.

We report on the incorporation of gold into silicon at a peak concentration of 1.9 × 1020 at./cm3, four orders of magnitude above the equilibrium solubility limit, using pulsed laser melting of a thin film deposited on the silicon surface. We vary the film thickness and laser process parameters (fluence, number of shots) to quantify the range of concentrations that can be achieved. Our approach achieves gold concentrations comparable to those achieved with ion implantation followed by pulsed laser melting, in a layer with high crystalline quality. This approach offers an attractive alternative to ion implantation for forming high quality, high concentration layers of transition metals like gold in silicon.

Fabrication of p-Si(111) layers with Ti levels well above the solid solubility limit was achieved via ion implantation of 15 keV 48Ti+ at doses of 1012 to 1016 cm−2 followed by pulsed laser melting using a Nd:YAG laser (FWHM = 6 ns) operating at 355 nm. All implanted layers were examined using cross-sectional transmission electron microscopy, and only the 1016 cm−2 Ti implant dose showed evidence of Ti clustering in a microstructure with a pattern of Ti-rich zones. The liquid phase diffusivity and diffusive velocity of Ti in Si were estimated to be 9 × 10−4 cm2/s and (2 ± 0.5) × 104 m/s, respectively. Using these results the morphological stability limit for planar resolidification of Si:Ti was evaluated, and the results indicate that attaining sufficient concentrations of Ti in Si to reach the nominal Mott transition in morphologically stable plane-front solidification should occur only for velocities so high as to exceed the speed limits for crystalline regrowth in Si(111).

Au-hyperdoped Si produced by ion implantation and pulsed laser melting exhibits sub-band gap absorption in the near infra-red, a property that is interesting for Si-photonics. However, the subband gap absorption has previously been shown to be thermally metastable. In this work, we study the atomistic processes that occur during the thermal relaxation of Au-hyperdoped Si. We show that the first step in thermal relaxation is the release of substitutional Au from lattice sites. This process is characterised by an activation energy of around 1.6 eV, a value similar to that associated with Au diffusion in Si, suggesting that both processes could be rate limited by the exchange of substitutional and interstitial Au atoms. As the system further relaxes, Au is found to locally diffuse and become trapped at nearby lattice defects, notably vacancies and vacancy complexes. In fact, DFT results suggest that the formation of Au dimers is energetically favourable after the Au becomes locally trapped. The dimers could subsequently evolve into trimers, etc., as other diffusing Au atoms become trapped at the dimer. At low Au concentrations, this clustering process does not form visible precipitation after annealing at 750 o C for 3 minutes. In contrast, spherical Au precipitates are found in samples with higher Au concentrations (> 0.14 at. %), where the Au atoms and the associated lattice defect distributions are laterally inhomogeneous.

No abstract