Quantum computing is one of the most exciting (and touted) fields of research at the moment, but if you ask a scientist how far away quantum computers are from ‘doing it’, you’ll get the classic scientific answer of ‘five to 10 years’.
So if a new quantum reality is still potentially a decade away, how far are we from personal quantum technology on our computer or laptop?
Although there are still some very large barriers to overcome in quantum computing, some research groups are already connecting very small quantum processors to traditional computers, and the future (as far as possible) looks bright.
“With quantum computing, you are harnessing a physical phenomenon that might not otherwise have been exploited,” says Dr. Andrew Horsley, CEO of Quantum Brilliance, an Australian team working on diamond-based quantum technology.
“The last time we did that was with electricity; it’s a pretty big change in the technological foundations of society.”
One of the reasons quantum computing has been so difficult to get off the ground is that the architecture that supports it needed to be built entirely from scratch.
Quantum computers do calculations using “qubits,” the quantum equivalent of computing “bits.” But instead of being on or off (0 or 1 in binary), the qubit can be a mix of 0 and 1. Imagine a qubit as a globe or a spinning atom where the state of the qubit is a point on the globe creating a mix between 0 and 1 in both longitude and latitude.
Unfortunately, the price of adding quantum to these bits is much more room for noise: random variations that can change the value of the result. Without specialized error correction, this can mean that the qubit is providing the wrong value. Even Google’s 2019 Quantum Supremacy Demonstration it was 99% noise and only 1% signal.
Even though our systems are slowly improving over time, we are still in what is known as the noisy intermediate scale quantum era. This means that even though we have the technology to build systems of up to a couple of hundred qubits, systems are still incredibly sensitive to their surroundings and can lose “coherence” after only a few seconds of work.
The actual physical materials that we are using to make quantum computers are not helping at all.
“In a classical system, hard drives are made of magnetic memory, and the magnetic material has the property of retaining a memory of its state for a long time…nature actually fixes us a lot of bugs for free,” says Tom . Stace, Deputy Director of the ARC Center of Excellence in Quantum Systems Engineering in Queensland.
“For quantum computers, we don’t have an analog substance. We don’t have something that preserves quantum states indefinitely. So we really have to design something that is like a quantum magnet, because something that is capable of storing quantum information indefinitely doesn’t exist in nature in any form.”
There have been multiple approaches to this problem.
Groups like IBM and Google are using “superconducting transmon” qubits made from materials like niobium and aluminum on silicon. some teams, such as the quantum group at the University of New South Wales are using silicon and phosphorous atoms to do “semiconductor” quantum computing, while Quantum Brilliance is using nitrogen atoms inside a diamond lattice to create their diamond-based qubits.
Each of these technologies has its pros and cons.
superconducting qubits are better developed and more accurate, but still have a high signal-to-noise ratio compared to traditional computers. These qubits can also more easily “interact” with each other, which is an important way to scale this technology. However, this makes them incredibly complex machines. As Stace describes it, they are “all the way” qubits, needing physical qubits in one section to correct errors and logical qubits in another area to do the actual calculation.
Then there’s the problem of temperature: being a superconductor means the machine must be near absolute zero temperatures. even if you I might put that on a laptop, the power cost to run it means you probably don’t want to.
Silicon and diamond are not as advanced as their supercomputing counterparts when it comes to noise and error correction, but they do have the advantage of not having to be in very cold temperatures.
silicon qubits recently achieved over 99% accuracy, which is an exciting milestone. It means that researchers can begin to implement error correction in the same way that superconducting qubits do. But this technology still requires cooler temperatures and has only two qubits in a system, so there’s still a long way to go before it’s ready for scale manufacturing.
Then there are the diamond-based qubits. The technology itself has similar problems to silicon, although diamond qubits can be run at room temperature, but Quantum Brilliance is apparently much more advanced, and the team will soon provide a quantum chip to the Pawsey Supercomputer Center in Perth.
“Diamond is one of the most widely used quantum technologies, but it’s mostly only used for sensing,” says Horsley. “It is at room temperature, it is a very simple system, it has a very high performance.
“The challenge has been scaling it beyond a handful of qubits.”
The reason it’s hard to climb is because of the particular way they’re made. In a process known as shotgun implantation, nitrogen atoms or electrons are fired at a piece of synthetic diamond to create something called a “nitrogen vacancy center.” The problem is that despite a lot of atoms being fired, researchers may only get one or two of these at the right level to be used as a qubit.
Instead, the Diamond Brilliance team is working on a system where they implant the nitrogen vacancy, and then they grow more diamonds, and then they implant another nitrogen vacancy, and so on.
They have big plans for a 50-qubit system built this way, which would make the technology useful for implementation with a classical computer to speed up time-sensitive and processor-intensive requests like speech-to-text, particularly where it would be necessary. It will not be easy to access the cloud and additional processing power.
However, this goal is still a long way off: despite exciting new software to connect the quantum system to the classical one, the box going to the Pawsey center has only two lone qubits.
“The really exciting thing about that is less computing power, [and] more than we’ve been able to take a really complex set of tabletop systems, put it in a box and ship it 3,500 kilometers away and run it in a supercomputing center there,” says Horsley.
“I’m very curious, what are all the weird things that [that will stem from] simply have a box in your facility?
Quantum computing: don’t give up
Although there are some very big technological hurdles to overcome before quantum computing can be in our lives, both Stace and Horsley suggest not giving up on dreams of owning a personal quantum laptop.
“If you go back to the 1940s and people were inventing the first serious digital computers, you couldn’t even ask the question, ‘Will we have a laptop?’ because no one could even conceive of that as something to have,” says Stace.
“The challenges that you would have had to anticipate solving back then would be somewhat inconceivable, but we have solved it nonetheless 80 years later. I believe that everything is possible.