Researchers make breakthrough in optical quantum computing

• Results can form the basis for a future universal photonics quantum processor operating in a single spatial mode.
• Experiment observed quantum interference among up to eight photons, surpassing the scale of most of existing experiments.

An international collaboration of researchers has made a notable advancement in optical quantum computing, paving the way for more scalable quantum technologies.

Quantum and optical computing are both technologies that could revolutionise data processing and computation. They have different advantages and disadvantages:

Quantum computing: Uses the quantum-mechanical properties of materials and photons that have values of 1 or 0, as well as a combined 1/0 state, called qubits. Quantum computers are faster and more parallel, but they are prone to errors if the hardware gets too warm. They must also run in a laboratory at sub-zero temperatures.

Optical computing: Also known as photonic computers, these are regular computers that use light instead of electrical power. Optical computers use photons, the particle form of light, to perform calculations. They can operate at much higher speeds than traditional electronic computing

Researchers, led by Philip Walther at University of Vienna, have successfully demonstrated quantum interference among several single photons using a novel resource-efficient platform.

It involves harnessing the properties of light, such as its wave-particle duality, to induce interference patterns, enabling the encoding and processing of quantum information.

They demonstrated a resource-efficient architecture for multiphoton processing based on time-bin encoding in a single spatial mode by using an efficient quantum dot single-photon source and a fast programmable time-bin interferometre to observe the interference of up to eight photons in 16 modes, all recorded only with one detector, thus considerably reducing the physical overhead previously needed for achieving equivalent tasks.

The results can form the basis for a future universal photonics quantum processor operating in a single spatial mode.

“In our experiment, we observed quantum interference among up to eight photons, surpassing the scale of most of existing experiments. Thanks to the versatility of our approach, the interference pattern can be reconfigured and the size of the experiment can be scaled, without changing the optical setup,” first author Lorenzo Carosini said.

He added that the results demonstrate the significant resource efficiency of the implemented architecture compared to traditional spatial-encoding approaches, paving the way for more accessible and scalable quantum technologies.

Manipulates the time domain of photons

In traditional multi-photon experiments, spatial encoding is commonly employed, wherein photons are manipulated in different spatial paths to induce interference.

These experiments require intricate setups with numerous components, making them resource-intensive and challenging to scale. In contrast, the international team, opted for an approach based on temporal encoding.

“This technique manipulates the time domain of photons rather than their spatial statistics. To realise this approach, they developed an innovative architecture at the Christian Doppler Laboratory at the University of Vienna, utilising an optical fibre loop. This design enables repeated use of the same optical components, facilitating efficient multi-photon interference with minimal physical resources,” Carosini saod.