Breakthrough in Silicon Qubits, Photonics Accelerates Quantum Internet

Render for T Center qubit
A render for a single T centre qubit in the silicon lattice, which supports the first single spin to ever be optically observed in silicon. The constituents of the T centre (two carbon atoms and a hydrogen atom) are shown as orange, and the optically-addressable electron spin is in shining pale blue. (Image credit: Photonics)

Researchers from Simon Fraser University may have just released the photonic springs that accelerate the quantum internet. In a paper published in Nature, the researchers demonstrated an emergent capacity in silicon qubits to produce a "photonic link" between each other. Furthermore, this same photonic capability may be easily integrated with the existing fiber optic infrastructure that already carries data across a reasonable (yet still insufficient) portion of society. That is bound to provide immense savings on deploying a quantum internet - and as we all know, the cost is (mostly) king.

The authors' paper describes observations carried on particular types of qubits: "T-center" photon-spin qubits, a kind of qubit that takes advantage of a specific luminescent defect in silicon - more specifically, InGaAs (Indium gallium arsenide), also explored in CPU manufacturing technologies. Silicon qubits have already shown remarkable coherence times - which relate to how resistant qubits are to outside interferences that would cause them to collapse and lose their information in the process, becoming unusable for the workload at hand.

And with more fantastic coherence times - and the comparative ease with which these "T center" qubits can be linked - comes the capability to perform more and more significant calculations. In their experiment, the researchers observed the effect in over 1,500 T Center qubits, ensuring they can replicate it - a healthy indicator for the potential scalability of their solution.

"This work is the first measurement of single T centers in isolation, and actually, the first measurement of any single spin in silicon to be performed with only optical measurements," said Stephanie Simmons, Canada Research Chair in Silicon Quantum Technologies.  

"An emitter like the T center that combines high-performance spin qubits and optical photon generation is ideal to make scalable, distributed, quantum computers," she continued, "because they can handle the processing and the communications together, rather than needing to interface two different quantum technologies, one for processing and one for communications."

Some qubit solutions in the market already use photonics to enable scaling between individual Quantum Processing Units (QPUs) - such as the diamond-based qubits from Quantum Brilliance. However, others don't naturally possess the ability to send information through photonics without coupling a complementary system. It, in turn, adds one more step in the quantum information chain, introducing variables in a technology that is erratic enough to any variations in its environment. The cost of pairing both technologies is also another factor to consider.

"T Center" photon-spin qubits, on the other hand, already emerge from a light-based phenomenon. Furthermore, they emit light at the same wavelength today's fiber communications and telecom networking equipment use - while retaining a >99% fidelity.

"With T centers, you can build quantum processors that inherently communicate with other processors," Simmons says. "When your silicon qubit can communicate by emitting photons (light) in the same band used in data centers and fiber networks, you get these same benefits for connecting the millions of qubits needed for quantum computing."

There's another inherent advantage towards silicon-based qubits: manufacturability. The tech industry has been manufacturing silicon-based transistors for decades already, and we're now reaching the point where even silicon manufacturing has to consider quantum effects. As a result, the quantum and silicon industries could converge and bring benefits of scale - and importantly, cost - towards a sector expected to be worth a cool $4531.04 billion by 2030.

"By finding a way to create quantum computing processors in silicon, you can take advantage of all of the years of development, knowledge, and infrastructure used to manufacture conventional computers, rather than creating a whole new industry for quantum manufacturing," Simmons concluded. "This represents an almost insurmountable competitive advantage in the international race for a quantum computer."

And indeed, it may very well be.

Francisco Pires
Freelance News Writer

Francisco Pires is a freelance news writer for Tom's Hardware with a soft side for quantum computing.