A single qubit on a standard silicon transistor chip has been successfully demonstrated as "quantum capable" in a new study by the UCL spinout Quantum Motion, led by researchers at UCL and Oxford University.

The qubit is the building block of quantum supercomputing, analogous to the bit in classical computers. To perform error-free calculations, quantum supercomputers of the future are likely to need at least millions of qubits. The latest study, published in the journal PRX Quantum, suggests that these computers could be made with industrial-grade silicon chips using existing manufacturing processes, instead of adopting new manufacturing processes or even newly discovered particles.

For the study, researchers were able to isolate and measure the quantum state of a single electron (the qubit) in a silicon transistor manufactured using a 'CMOS' technology similar to that used to make chips in computer processors.

Furthermore, the spin of the electron was found to remain stable for a period of up to nine seconds. The next step is to use a similar manufacturing technology to show how an array of qubits can interact to perform quantum logic operations. 

Professor John Morton (London Centre for Nanotechnology at UCL), the co-founder of Quantum Motion, said: "We're hacking the process of creating qubits, so the same kind of technology that makes the chip in a smartphone can be used to build quantum computers.

"It has taken 70 years for transistor development to reach where we are today in computing and we can't spend another 70 years trying to invent new manufacturing processes to build quantum computers. We need millions of qubits and an ultra-scalable architecture for building them, our discovery gives us a blueprint to shortcut our way to industrial-scale quantum chip production."

The experiments were performed by Ph.D. student Virginia Ciriano Tejel (London Centre for Nanotechnology at UCL) and colleagues working in a low-temperature laboratory. During operation, the chips are kept in a refrigerated state, cooled to a fraction of a degree above absolute zero (?273 degrees Celsius).

Ms Ciriano Tejel said: "Every physics student learns in textbooks that electrons behave like tiny magnets with weird quantum properties, but nothing prepares you for the feeling of wonder in the lab, being able to watch this 'spin' of a single electron with your own eyes, sometimes pointing up, sometimes down. It's thrilling to be a scientist trying to understand the world and at the same time be part of the development of quantum computers." 

A quantum computer harnesses laws of physics that are normally seen only at the atomic and subatomic level (for instance, that particles can be in two places simultaneously). Quantum supercomputers could be more powerful than today's supercomputers and capable of performing complex calculations that are otherwise practically impossible. 

While the applications of quantum computing differ from traditional computers, they will enable us to be more accurate and faster in hugely challenging areas such as drug development and tackling climate change, as well as more everyday problems that have huge numbers of variables - just as in nature - such as transport and logistics.

In a potential boost for quantum supercomputing and communication, a European research collaboration reported a new method of controlling and manipulating single photons without generating heat. The solution makes it possible to integrate optical switches and single-photon detectors in a single chip.

Publishing in an academic journal, the team reported having developed an optical switch that is reconfigured with microscopic mechanical movement rather than heat, making the switch compatible with heat-sensitive single-photon detectors.

Optical switches in use today work by locally heating light guides inside a semiconductor chip. "This approach does not work for quantum optics," says co-author Samuel Gyger, a PhD student at KTH Royal Institute of Technology in Stockholm. 

"Because we want to detect every single photon, we use quantum detectors that work by measuring the heat a single photon generates when absorbed by a superconducting material," Gyger says. "If we use traditional switches, our detectors will be flooded by heat, and thus not work at all."

The new method enables control of single photons without the disadvantage of heating up a semiconductor chip and thereby rendering single-photon detectors useless, says Carlos Errando Herranz, who conceived the research idea and led the work at KTH as part of the European Quantum Flagship project, S2QUIP.

Using microelectromechanical (MEMS) actuation, the solution enables optical switching and photon detection on a single semiconductor chip while maintaining the cold temperatures required by single-photon detectors.

"Our technology will help to connect all building blocks required for integrated optical circuits for quantum technologies," Errando Herranz says.

"Quantum technologies will enable secure message encryption and methods of computation that solve problems today's computers cannot," he says. "And they will provide simulation tools that enable us to understand fundamental laws of nature, which can lead to new materials and medicines."

The group will further develop the technology to make it compatible with typical electronics, which will involve reducing the voltages used in the experimental setup.

Errando Herranz says that the group aims to integrate the fabrication process in semiconductor foundries that already fabricate on-chip optics - a necessary step in order to make quantum optic circuits large enough to fulfill some of the promises of quantum technologies.