The project's ultimate goal is to construct a quantum simulator based on NV centers in diamond. As detailed in the description of the action, several intermediate steps are required toward reaching this goal. These objectives are described below, along with the relevant achievements made in the project:
- Sample preparation: Relevant diamond samples (with high NV density and good coherence properties) are not available (either commercially or otherwise), and must be designed and fabricated specifically. For that purpose, we have employed commercial nitrogen ion implantation into high-purity samples purchased, creating the desired nitrogen concentration, although at a lower NV concentration than desired. We have then developed a local electron irradiation process using our in-house TEM (transmission electron microscope) system, increasing our NV concentration by an order of magnitude, thus reaching the NV-NV interaction regime, without adversely affecting the NV coherence properties (since no additional noise sources have been incorporated).
We are further studying novel surface termination techniques (in collaboration with Alon Hoffman’s group at the Technion) to enhance the quantum properties shallow NVs.
- Noise characterization: The coherence properties of NVs must be studied and understood precisely in order to reach the desired parameters and properly fabricate the diamond substrate. We have developed a novel noise spectroscopy scheme, based on continuous, phase modulated driving of the NV, which acts as a sensor for the noise affecting it. This technique, referred to as gDYSCO, provides enhanced resolution and accuracy in extracting the noise spectrum of non-monotonous sources. We showed that combining this approach with our previously demonstrated pulsed techniques can optimize resolution, accuracy and bandwidth.
- Many-body Hamiltonian engineering: Advanced control techniques are required in order to identify and modify NV-NV interactions, enabling precise determination of the system parameters (specifically in the presence of noise), as well as the engineering of desired interacting Hamiltonians in order to simulate quantum many-body problems of interest. We devised a protocol consisting of combined dynamical decoupling and homonuclear decoupling sequences to characterize the interacting spin system. In addition, we have developed a novel theoretical framework for general Hamiltonian engineering in interacting spin-1/2 systems, utilizing a group theory approach and an extended symmetry group (icosahedral symmetry) compared to the cubic group used before. We have shown that this framework leads to complete control over the quantum interacting spin system, beyond the capabilities afforded by the previous approach.
- Design superconducting couplers: We have analyzed the problem using a Green's function approach, leading to analytical, closed-form expressions for somewhat simplified, yet relevant, geometries. These results are helpful in determining the functional dependence of the couplers' performance on various parameters (such as shape and distance), informing the design and fabrication of these structures. We have also expanded our analysis to more complex geometries.
