The buzz surrounding the future of quantum technology continues to increase as researchers try to tap into the potential of superimposed, entangled and tunneling quantum particles. These particles have the unique ability to exist in two states simultaneously, which can greatly increase power and efficiency in many applications.

According to Kamyar Parto, Ph.D. University of California, Santa Barbara student and co-author of a published article Nano Letters, the current state of quantum devices is “where the computer was in the 1950s,” or at the very beginning of its development. Parteau works in the lab of Galan Moody, a renowned expert in quantum photonics and associate professor in the Department of Electrical and Computer Engineering. The article details a major breakthrough in this area, the creation of a “factory” on a chip to generate a stable and fast stream of single photons, critical for the development of photonics-based quantum technologies.

In the early stages of computer development, Parteau explained, “Researchers had just made a transistor and had ideas on how to make a digital switch, but the platform was weak. Different groups developed different platforms and eventually they all merged into CMOS (Complementary Metal Oxide Semiconductor). Then semiconductors. We had a big explosion around it.

“Quantum technology is in the same position – we have an idea and a feeling of what we can do with it, and there are many competing platforms, but there is no clear winner yet,” he continued. “You have quantum computers based on superconducting qubits, spin qubits in silicon, electrostatic spin qubits, and ion traps. Microsoft is trying to create topologically protected qubits, and we’re working on quantum photonics at Moody Lab.”

Pareto predicts that the winning platform will be a combination of different platforms, given that each has strengths but also limitations. “For example, it’s very easy to transmit information using quantum photonics because light likes to move,” he said. “However, a spinning qubit makes it easy to store information and do some local ‘stuff’ on it, but you can’t move that data around. So why not try using photonics to move data from a platform that stores better and convert it back to another format while we’re there?”

Qubits, these surprising drivers of quantum technology, are of course different from classical bits, which can only exist in a single zero or one state. Qubits can be both one and zero at the same time. In the field of photonics, Pareto said, it can be done for a single photon to exist (a state) or not (a state of zero).

This is because a single photon forms a so-called two-level system, meaning it can exist in the zero state, in the single state, or in any combination, such as 50% one and 50% zero, or maybe 80% one and 20. % none. At Moody Group this can be done regularly. The challenge is to generate and collect individual photons with very high efficiency, for example by directing them onto a chip using waveguides. Waveguides, exactly as the name suggests, direct light where it needs to go, similar to how wires direct electricity.

“If we put these individual photons in many different waveguides – thousands of individual photons in each waveguide – and somehow choreograph how the photons move along the waveguides on the chip, we can do quantum computing,” Parteau said.

While using waveguides to guide photons on a chip is relatively simple, extracting a single photon is not easy and building a system that quickly and efficiently produces billions of photons is much more difficult. A new paper describes a technique that uses a peculiar phenomenon to generate single photons with a much higher efficiency than has been achieved before.