Research efforts seeks diamond-based Quantum processors

A joint research project that includes Quantum Brillance, Fraunhofer Institute for Applied Solid State Physics IAF and the University of Ulm aims to develop new techniques for fabrication and control of diamond-based quantum microprocessors.

Fraunhofer IAF and Quantum Brilliance, the Australian-German quantum computing hardware company, are jointly developing precision manufacturing techniques to fabricate scalable diamond qubit arrays. In addition, Fraunhofer IAF will develop growth processes for diamond substrates. The Quantum Brilliance team has exclusive use of Fraunhofer IAF’s facility in Freiburg, Germany. Researchers at the University of Ulm’s Institute for Quantum Optics are developing scalable readout and control techniques for diamond-based qubits.

Development of quantum technologies would benefit from miniaturization. Quantum Brillance leverages synthetic diamonds that can be miniaturized to operate in real-world environments. The goal of the €19.9 million ($22.5 million) “Deutsche Brilliance” collaboration is solving key challenges affecting diamond-based quantum computers. Efforts include developing new methods for selective initialization, reading and manipulation of qubits in quantum computers with multiple processor nodes.

The collaborators said solving such challenges by 2025 will serve as development milestone toward commercialization of quantum computers. According to Mark Mattingley-Scott, general manager EMEA for Quantum Brilliance, research will also focus on how qubits are read out and accessed. The partners’ approach uses off-the-shelf technology comparable to that used in signal processing for 3G, 4G and 5G networks.

Nitrogen-Vacancy

Quantum Brilliance’s technology is based on synthetic diamonds that could eventually serve as the brains of future computers. Diamond-based quantum accelerators can run at room temperature, requiring only tens of qubits. “Diamond quantum microprocessors are the qubits,” Mattingley-Scott said, “analogous to the Intel 4004–the very first general-purpose microprocessor [based on] diamond. The Intel 4004 was a simple general-purpose computer with a four-bit microprocessor that contained 2,300 transistors developed to run a portable calculator.”

“For comparison, our technology is the first quantum microprocessor using diamonds. Fifty qubits is…equivalent to the 3,700 transistors of the 4004, not in terms of computational power but in terms of the stage of the technology. A 512-gigabyte USB stick contains 8 trillion transistors, and diamond will be the only way to scale in the same way.”

The company uses  Nitrogen-Vacancy (NV) diamond technology to create qubits. The method incorporates nitrogen atoms with an adjacent vacancy site within a carbon diamond lattice. The NV center can be forced into a spin-up, spin-down or superposition of these states by light and microwave signals to control the qibit state.

“Nitrogen vacancy qubits are currently created through a ‘shotgun’ approach by firing nitrogen atoms or electrons at diamond and then performing a very labor-intensive task to search the diamond for some nitrogen vacancies at just the right depth,” Mattingley-Scott added.

“One diamond will likely yield a handful of nitrogen vacancies.” The joint “project will focus on another way of creating these nitrogen vacancies. We don’t use energies to accelerate nitrogen into the diamond, but rather we chemically deposit the nitrogen onto the diamond. We then use a sort of scalpel to select where we want the nitrogen vacancies, and where we do not. This eliminates the process of searching for the nitrogen vacancies, turning the traditional process on its head, and saving significant time.”

The process “guarantees we’re going to get those nitrogen vacancies in the right numbers in the places where we’ve defined them,” he continued. “The project is a way of taking something [that] is very difficult to control and very difficult to get sufficient yield [and turning it] into something which is much more predictable. This will make all the difference once the process is automated.”

Unlike huge quantum computing mainframes requiring energy-intensive cooling, quantum “accelerators” based on synthetic diamonds come in small form factors and operate at room temperature, meaning they could be used in a range of real-world scenarios.

Mattingley-Scott noted that quantum computing developers face challenges creating usable qubits. “Tech giants are saying they’ve reached 100 or so qubits, but there isn’t anything you can do with them now and you have to apply all this complex, expensive equipment and special conditions to make them happen,” he asserted. “There’s also the issue of crosstalk created by magnetic spin, which is one of the elephants in the room in quantum computing.

“We expect we’ll be able to achieve high-performance levels with diamond-based technology with significantly less qubits needed to achieve the same performance [delivered by] other quantum technologies.” The startup also claims it will be able to outperform GPUs, for example, of similar size, weight and power using just a few qubits.

“A scalable manufacturing process that delivers incremental performance benefits will see the quantum industry’s growth mimic what the semiconductor industry has seen the past 60 years,” the company further claims.

Another advantage is the technology’s ability to operate at room temperature while providing high-quality qubits that are stable and less affected by environmental noise. The diamond technique employs a hybrid mix of physical features derived from quantum mechanical systems, rather than merely the magnetic properties employed by other quantum technologies, helping to limit errors.

The challenge with NV diamond technology has been scaling up to more qubits. Quantum Brilliance’s processors are expected to be the size of a graphics card, reaching 50 qubits by 2025, Mattingley-Scott said. It also aims to create a single-chip quantum accelerator. “Then you will be able to install thousands of them in your computing center and have lots of [nodes] of quantum coherence for massive parallelization of quantum computations.” The startup is also investigating algorithms best suited for greater parallelism.

Among the deployment goals is demonstrating the ability to outperform digital processors of comparable size, weight and power. “A small module that consumes the same power as a PC or laptop can be integrated everywhere,” Mattingley-Scott asserted. “When massive parallelization is achieved, the business case for additional applications will be difficult to ignore compared to more capital-intensive types of quantum computing.”