A Qubit in Hand May Be Quite Fundamental, But Diamonds Are a Network’s Best Friend

Quantum networks are an emerging area of quantum technology that aim to connect quantum computers through quantum communication channels. They are the quantum equivalent of the internet connecting classical computers. These networks enable the transfer of quantum information over long distances and have the potential to revolutionise secure communication, distributed quantum computing, and quantum sensing. But building a quantum network isn’t straightforward. Surprisingly, diamonds play a crucial role in the development of quantum networks. Diamonds aren’t just a girl’s best friend; they also form the backbone of this quantum technology. When we tweak a diamond’s structure by replacing two carbon atoms in its lattice with a nitrogen atom and an empty space—creating what we call a nitrogen-vacancy (NV) centre—we turn the diamond into a powerful component for quantum networks. These
NV centres serve as qubits, the basic units of quantum information, akin to bits in traditional computing. Using NV centres, diamonds exhibit unique properties that make them excellent candidates for storing and processing quantum information.

My research focuses on an even deeper layer of this technology: ensuring the stability and control of the very core components of our quantum bits—the spins of atomic nuclei. Spins are like tiny magnets inside the nuclei and electrons of atoms. In our quantum network, controlling how these nuclear and electron spins interact can be compared to operating a switch. This control is crucial because it allows us to manage how quantum information is processed and transmitted within our network. My work aims to keep these spins stable and determine the optimal conditions for these interactions, ensuring that our quantum network is efficient and reliable. The controlled spins can influence the state of photons (packages of light) that interact with the NV centres. When photons pass through or interact with these controlled spins in NV centres, their quantum state can become entangled with the spins. This entanglement between photons and spins is what enables the photons to carry quantum information across the network. Essentially, the photons become messengers that carry the quantum information encoded by the spins, and their patterns of entanglement are what we use to transmit data securely. By perfecting this control and interaction, we enhance the network’s ability to process and transmit quantum information reliably and securely, moving us closer to a new era of communication.

Niamh Mulholland

NanoDTC PhD Student, c2023