We discuss the possibility of realizing quantum computation on the basis of a cluster of single interacting nuclear spins in solids. This idea seems to be feasible because of the combination of two techniques—Single Molecule Spectroscopy and Optically Detected Electron Nuclear Double Resonance. Compared to the well-known bulk Nuclear Magnetic Resonance (NMR), the proposed method of quantum computation has the advantage that quantum computation is performed with pure spin states and the quantum processor is more easily scalable. At the same time, the advantages of NMR quantum computation are kept: long coherence time and easy construction of quantum gates. As a specific system to implement the above idea, we discuss the ¹³C-nuclear spins in the nearest vicinity of a single nitrogen-vacancy (NV) defect center in diamond, which can be optically detected using the technique of scanning confocal microscopy. Owing to the hyperfine coupling of the ground state electron paramagnetic spin S=1 of the center to ¹³C nuclear spins in a diamond lattice, the states of nuclear spins in the vicinity of the defect-center can be addressed individually. Preliminary consideration shows that it should be possible to address up to 12 individual ¹³C nuclear spins. The dephasing time of the nuclear spin states at low temperatures allows realization up to 10⁵ gates.

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.

We predict the characteristics of hyperfine interactions (hfi) for a number of electron-nuclear spin systems NV-¹³C in diamonds grown by seeding approach from the specific isotopic aza-adamantane or methyl-aza-adamantane molecules differing in ¹³C position in the precursor as well as in the orientation of the NV center in the post-obtained diamond. For the purpose we have used the spatial and hfi data simulated previously for the cluster C₅₁₀[NV]^–H₂₅₂. The data obtained can be used to identify (and correlate with the precursor used) the specific NV-¹³C spin system by measuring the hfi-induced splitting in optically detected magnetic resonance spectra being characteristic for the NV-¹³C system.