Networking goes quantum

December 13, 2018, University of Bristol
Artist's impression of the entanglement-based quantum network. The infinity symbols represent ‘entanglement’ which is the ability of measurement outcomes of different particles to be correlated instantly regardless of the distance between them. Entanglement is used as a resource to enable every user to securely communicate with every other user. Credit: Murali Krishna - Artist /Designer -

A scientist involved in expanding quantum communication to a network of users, is continuing his work at the University of Bristol.

The enhanced offered by has been historically limited to two partner exchanges. Now, for the first time, scientists have connected multiple users simultaneously on a quantum encrypted without using trusted nodes.

Researchers from the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences, together with a collaborator from the Austrian Institute of Technology (AIT), report on the simple, seamless, cheap and secure network in the latest issue of the journal Nature, published today.

Co-author of the paper Dr. Siddarth Joshi who recently moved to the University of Bristol and is continuing to develop in the Quantum Engineering Technology Labs, said: "We created a very versatile quantum communication network where every user can talk to every other user simultaneously.

"We plan to build even bigger networks with many more users, with the goal to create a versatile foundation for building a quantum internet."

The Viennese team achieved the long-awaited quantum network using a novel architecture based on a new method of distributing a basic resource of quantum communication-entanglement.

An entangled system is one which is interconnected to such a degree that the individual parts can't be fully described in isolation.

Entangled light particles, photons, are the fundamental resource used in quantum communication to distribute a secure encryption key. The Viennese team's key innovation was in producing photons such that only certain wavelengths entangle with each other.

Like a rainbow, the signal was split into different 'colours' and distributed cleverly between the users, who then only required basic modules to connect to the single source of entanglement.

Dr. Joshi said: "By using quantum entanglement and standard passive telecommunication techniques of wavelength-based multiplexing we were able to interconnect four users in a network architecture that is scalable and requires minimal resources."

Unlike previous efforts to create such a network, this new scheme allows all users to simultaneously communicate with all other users without using trusted nodes to relay the message. With no complex steps to route the entanglement to different users, the network is versatile, cheap and reliable.

The extension of point-to-point connections to networks represents an important step in the direction of a " internet" and the researchers argue that their four-user network can be scaled to incorporate more connections.

Dr. Joshi said: "The number of users is limited by available wavelength channels and the desired fully connected network topology. However, we are working on a new scheme that will allow even more users to connect to the network.

"To achieve this, we plan on improving the scalability of the network presented in the Nature paper by changing the way we multiplex to allocate channels to each user.

"We aim to create a network that can support different types of users in different configurations that can dynamically change depending on current network traffic. The network also requires optimal routing, redundancy of paths and a degree of anonymity."

Explore further: An important step towards completely secure quantum communication network

More information: Sören Wengerowsky et al. An entanglement-based wavelength-multiplexed quantum communication network, Nature (2018). DOI: 10.1038/s41586-018-0766-y

Related Stories

Scientists make first 'on demand' entanglement link

June 13, 2018

Researchers at QuTech in Delft have succeeded in generating quantum entanglement between two quantum chips faster than the entanglement is lost. Via a novel smart entanglement protocol and careful protection of the entanglement, ...

Worldwide quantum web may be possible with help from graphs

June 8, 2016

(—One of the most ambitious endeavors in quantum physics right now is to build a large-scale quantum network that could one day span the entire globe. In a new study, physicists have shown that describing quantum ...

Entangled LED first to operate in the telecom window

March 9, 2018

Researchers have demonstrated the first quantum light-emitting diode (LED) that emits single photons and entangled photon pairs with a wavelength of around 1550 nm, which lies within the standard telecommunications window. ...

For identical quantum channels, order matters

April 9, 2018

Physicists have demonstrated that using two quantum channels in different orders can enhance a communication network's ability to transmit information—even, counterintuitively, when the channels are identical. This result ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

Physicists reveal why matter dominates universe

March 21, 2019

Physicists in the College of Arts and Sciences at Syracuse University have confirmed that matter and antimatter decay differently for elementary particles containing charmed quarks.

ATLAS experiment observes light scattering off light

March 20, 2019

Light-by-light scattering is a very rare phenomenon in which two photons interact, producing another pair of photons. This process was among the earliest predictions of quantum electrodynamics (QED), the quantum theory of ...

How heavy elements come about in the universe

March 19, 2019

Heavy elements are produced during stellar explosion or on the surfaces of neutron stars through the capture of hydrogen nuclei (protons). This occurs at extremely high temperatures, but at relatively low energies. An international ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.