However, all these advances could mean nothing if scientists cannot reliably transmit quantum data over a network. Interestingly, quantum data is also prone to being lost when transmitted over long distances due to its nature.

This is why scientists have been looking for ways to divide the network into smaller segments and link them up to share the same quantum state.

Transmitting quantum information

Modern-day communication networks that transmit Internet data also suffer from the same problem. This is why the networks are equipped with repeaters or amplifiers that read and amplify the signal so that it remains intact over long distances.

Classical repeaters, however, cannot be used with quantum data since any attempt to read or copy it would destroy it. Therefore, quantum information must be stored and retrieved throughout the network to transmit data over long distances, requiring a quantum memory device.

One approach to sharing quantum information is using entangled photons. Since the particles are entangled, one cannot understand one of the particles without understanding the other.

However, to share the entangled photons over long distances, you need two devices: one to create, store, and retrieve them over the transmission network.

Quantum dot approach

Scientists have attempted to create such devices, but generating entangled photons on demand and developing a compatible quantum memory to store them has remained challenging.

This was largely because the devices used for creating and storing photons used different wavelengths, making it difficult for them to interface.

A collaboration of scientists at the Imperial College and the University of Southampton in the UK and the University of Stuttgart and the University of Wurzburg in Germany developed a device that uses the same wavelength.

Non-entangled photons, dubbed quantum dots, generated in this device were passed through a quantum memory system that stored them with the help of rubidium atoms.

A laser was used to turn the memory on and off and release the photons on demand. More importantly, the wavelength the device uses is compatible with the fiber optic infrastructure that connects the world today, making it easier to deploy when quantum computers are ready for roll-out.

“Interfacing two key devices together is a crucial step forward in allowing quantum networking, and we are really excited to be the first team to have been able to demonstrate this,” said Sarah Thomas, a researcher at the Department of Physics at Imperial College London, who was involved in the work in a press release.

The scientists plan to improve the system by reducing its size and increasing the duration of photon storage.