February 3, 2023

The diamond quantum  revolution

In the April 2020 issue of Physics World, editors explain how diamond, this special form of carbon, now has many practical quantum applications.

Here are some extracts.

Diamonds are well known as the gem for marking engagements and other special occasions, but the huge influence of this material in industry is all around us too. Diamond is used, for example, as a tool for machining the latest smartphones, as a window in high-power lasers used to produce automotive components, and even as a speaker-dome material in high-end audio systems. However, there is a new application on the horizon that could be even more profound – that of diamond quantum technologies.

At the turn of the 20th century, theoretical and experimental scientists were grappling to understand how the universe worked at very small scales. The results of this turned into the field of quantum mechanics, which has led to innovations – such as lasers and transistors – that impact our daily lives. These so-called “quantum 1.0” technologies rely on the effects of quantum mechanics, but now in the 21st century, scientists around the world are trying to develop the next wave of innovations. “Quantum 2.0” technology will rely on manipulating and reading out quantum states, and will typically exploit the quantum effects of superposition and entanglement.

The challenge of developing quantum technology is that quantum states are so fragile. Ideally these states would be isolated from everything else, but to make them useful you need to interact with them. Some applications can take advantage of this fragility – for example, in developing highly sensitive sensors – but they still need a degree of isolation to be controlled in the first instance. This balance between control and interaction is the fine line quantum scientists are having to traverse.

Trapped ions have exquisite quantum properties but are challenging to integrate, whereas circuits of superconductors can be fabricated but can only operate at cryogenic temperatures. This is where materials like diamond come into play as they offer a compromise by being solid-state – making it easier to integrate into devices – and operational at room temperature.

Diamond is now well established as a major player in quantum materials, with more than 200 academic groups around the world working on applications of its quantum properties. There is also a growing number of companies developing diamond quantum technology, including large firms such as Lockheed Martin, Bosch and Thales, as well as many start-ups such as Quantum Diamond TechnologiesNVision and Qnami. The material is at the heart of all of this technology, but lots of time-consuming engineering is required to make optimized devices. Even so, in many cases, potential customers are already testing prototype systems.

An additional barrier to device development is the learning curve required in getting the most out of the NV defect, which takes a skilled quantum physicist. This is where some of the national and international programmes in the UK, Europe and the US are helping by providing a supply of quantum scientists to organizations that do not have the relevant skills in-house. The final challenge is that it is impossible to say which of the diamond quantum technology applications will result in the most viable markets as the technology itself is so disruptive. So while we do not know how big an opportunity diamond quantum technologies might provide, one thing is clear: they are certainly here to stay.

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