The spin Hamiltonian method in combination with ab initio calculations of the spin characteristics of quantum registers that include an electron spin S = 1 of a single NV center in the ground electronic state and nuclear spins I = 1/2 of several atoms ¹³C located at different lattice sites near the vacancy of the NV center is applied to find eigenvalues and eigenfunctions of spin systems NV + n ¹³C for cases where the lattice sites nearest to the vacancy of the NV center contain one, two, or three ¹³C nuclear spins, as well as for cases where ¹³C atoms are located at sites more distant from the vacancy. For these single spin NV + n ¹³C systems, the spectra of optically detected magnetic resonance (ODMR) are calculated, which agree well with available experimental data.

Thermal conductivity κ(T) of single-crystal CVD diamond enriched with 13C isotope to 98.16% was measured by the method of steady-state longitudinal heat flow in the temperature range from 6 to 410 K. This crystal with low nitrogen impurity content (<50 ppb) showed thermal conductivity 2010±50 W m−1 K−1 at 300 K (with a maximum of 12 100 W m−1 K−1 at 83 K), which is significantly lower than that of diamond with natural isotopic composition: κ(300K)=2360±50 W m−1 K−1. The measured data were analyzed using first-principles theory and the Callaway model, taking into account phonon scattering in three-phonon processes, scattering at sample boundaries and at isotopes. The first-principles calculations overestimate the thermal conductivity compared to the measured one near and to the right of the κ(T) peak, indicating the presence of significant additional phonon scattering by lattice defects in the studied chemically pure diamond samples. The results of both theoretical approaches for thermal conductivity at 300 K are in good agreement with our measured data and other published experimental data for isotopically modified diamonds. First-principles calculations yield a thermal conductivity ratio of κ12(T)/κ13(T)=1.072 for monoisotopic defect-free 12C and 13C crystals at 300 K. This ratio decreases at high temperatures to a value of 1.041 according to the Leibfried–Schlömann theory and to a value of 0.921 at very low temperatures.

We present an experimental realization and characterization of artificial spiking neuron based on an optoelectronic pair “microcavity laser-single photon avalanche diode” operating in few photon regime. We show that basic properties of biological neurons, such as an existence of the threshold and the refractory period, the insensitivity to the effect of the stimuli strength above the threshold, and the dependence of the neuron fire rate of the stimuli strength, can be realized with such a type of artificial neuron. To compare, we present corresponding results of the numerical simulation in the framework of the FitzHugh–Nagumo neuron model.

One of the most promising platforms to implement quantum technologies are coupled electron-nuclear spins in diamond in which the electrons of paramagnetic color centers play a role of “fast” qubits, while nuclear spins of nearby ¹³C atoms can store quantum information for a very long time due to their exceptionally high isolation from the environment. Essential prerequisite for a high-fidelity spin manipulation in these systems with tailored control pulse sequences is a complete knowledge of hyperfine interactions. Development of this understanding for the negatively charged “silicon-vacancy” (SiV^–) and neutral (SiV⁰) color center, is a primary goal of this article, where we are presenting shortly our recent results of computer simulation of spatial and hyperfine characteristics of these SiV centers in H-terminated cluster C₁₂₈[SiV]H₉₈ along with their comparison with available experimental data.

Nanostructured diamonds hosting optically active paramagnetic color centers (NV, SiV, GeV, etc.) and hyperfine-coupled with them quantum memory ¹³C nuclear spins situated in diamond lattice are currently of great interest to implement emerging quantum technologies (quantum information processing, quantum sensing and metrology). Current methods of creation such as electronic-nuclear spin systems are inherently probabilistic with respect to mutual location of color center electronic spin and ¹³C nuclear spins. A new bottom-up approach to fabricate such systems is to synthesize first chemically appropriate diamond-like organic molecules containing desired isotopic constituents in definite positions and then use them as a seed for diamond growth to produce macroscopic diamonds, subsequently creating vacancy-related color centers in them. In particular, diamonds incorporating coupled NV-¹³C spin systems (quantum registers) with specific mutual arrangements of NV and ¹³C can be obtained from anisotopic azaadamantane molecule. Here we predict the characteristics of hyperfine interactions (hfi) for the NV-¹³C systems in diamonds grown from various isotopically substituted azaadamantane molecules differing in ¹³C position in the seed, as well as the orientation of the NV center in the post-obtained diamond. We used the spatial and hfi data simulated earlier for the H-terminated cluster C₅₁₀[NV]^-H₂₅₂. The data obtained can be used to identify (and correlate with the seed used) the specific NV-¹³C spin system by measuring, e.g., the hfi-induced splitting of the m_S = ±1 sublevels of the NV center in optically detected magnetic resonance (ODMR) spectra being characteristic for various NV-¹³C systems.