Self-assembling hybrid diamond-biological quantum devices at room temperature

Researchers have begun to self-assemble quantum components on the nanometer scale. This is beginning of a multi-decade process to revolutionize the computing.

An international team of physicists say they’ve used biological self-assembly techniques to make diamond-based prototypes of the quantum information storage devices of this type. That’s a development that has the potential to profoundly influence the future of computing.

The key to all this is nitrogen-vacancy centres in diamond which behave like single atoms. They can store photons, emit them again and interact with other nitrogen-vacancy centres nearby. In fact, their photon storage ability is legendary, holding them, and the information the carry, for periods stretching to milliseconds. At room temperature.

That’s significantly longer and more robust than other quantum information storage devices.

They modified a well known ring-shaped protein called SP1 so that it binds to diamond. In fact, they created 12 binding sites on this ring allowing it to hold six nanodiamonds in hexagonal formation.

They then used a laser to generate nanodiamonds just 5 nanometres across by blasting them off a larger crystal. They placed the resulting crystals in a liquid which they poured onto a layer of the modified SP1 rings.

Nanodiamond (ND)-SP1 arrays and clusters
(a) DF-STEM (Dark eld scanning transmission electron microscopy) image of ND structures on an SP1-ordered monolayer (ND diameter 5nm). The hexagonal arrangement in the white dashed square is magni ed in part (b). Yellow and red circles show diamond dimers and trimers, respectively, with inner distances of 11 nm.
(b) Enlarged section of the white dashed square of (a) showing a hexagonal structure formed of 7 NDs.
The symmetry and distances are determined by the underlying SP1-layer.
(c) SP1-protein ring: The inner linkers (binding
sites) are genetically modi fied to enable graphite speci c binding.
(d) Schematic of an ordered hexagonal array of SP1-NDs hybrids consisting of a ND attached to the SP1 inner cavity. Here the SP1-monolayer serves as a structural scaff old.
(e)SEM image of larger (ND diameter 30nm) clusters connected by SP1 and obtained in solution.

Arxiv – Self-assembling hybrid diamond-biological quantum devices (35 pages)


Summary

We proposed a new method to create scalable arrangements of NV-centers in diamond by exploiting the ability of biological systems for self-assembly along with the precise positioning of surface functionalized nanodiamonds in such structures. We experimentally realized and verifi ed the creation of ordered nanodiamond structures on a protein sca old, namely on a SP1 monolayer, as well as the SP1-assisted formation of nanodiamond clusters in solution. Based on the achievable NV distances on the nanometer scale we proposed and analyzed theoretically the implementation of single and multiqubit gates and demonstrated its application for the creation of cluster states, thereby addressing the typical problems as the limited coherence time and heterogeneous dipolar coupling strengths. Moderate decoupling fields around 1MHz, well within reach of current experimental setups, allow for the efficient decoupling from surface spin noise with coherence times comparable to the ultimate limit. Along with significant dipolar couplings of several tens of kHz and the viability of individual addressing, gate fidelities well above 95% can be expected even for multiple qubits and imperfect couplings. We believe that the combination of nanodiamonds with biological systems provides a promising approach towards scalability, overcoming the limitations of current attempts and offering a high level of control in the structure formation

ABSTRACT
The realization of scalable arrangements of nitrogen vacancy (NV) centers in diamond remains a key challenge on the way towards efficient quantum information processing, quantum simulation and quantum sensing applications. Although technologies based on implanting NV-center in bulk diamond crystals or hybrid device approaches have been developed, they are limited in the achievable spatial resolution and by the intricate technological complexities involved in achieving scalability. We propose and demonstrate a novel approach for creating an arrangement of NV-centers, based on the self-assembling capabilities of biological systems and its beneficial nanometer spatial resolution. Here, a self-assembled protein structure serves as a structural scaffold for surface functionalized nanodiamonds, in this way allowing for the controlled creation of NV-structures on the nanoscale and providing a new avenue towards bridging the bio-nano interface. One-, two- as well as three-dimensional structures are within the scope of biological structural assembling techniques. We realized experimentally the formation of regular structures by interconnecting nanodiamonds using biological protein scaffolds. Based on the achievable NV-center distances of 11nm, we evaluate the expected dipolar coupling interaction with neighboring NV-center as well as the expected decoherence time. Moreover, by exploiting these couplings, we provide a detailed theoretical analysis on the viability of multiqubit quantum operations, suggest the possibility of individual addressing based on the random distribution of the NV intrinsic symmetry axes and address the challenges posed by decoherence and imperfect couplings. We then demonstrate in the last part that our scheme allows for the high-fidelity creation of entanglement, cluster states and quantum simulation applications.

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