Securely “send” images over the network using only light

nature communications Research published by an international team from Wits and ICFO-Institute of Photonic Science demonstrates teleportation-like transmission of light “patterns”, the first method of transmitting images over a network without physically sending them. It is also a key step to realize quantum networks of high-dimensional entangled states.

Long-distance quantum communication is an integral part of information security and has been demonstrated through ultra-long distances of two-dimensional states (qubits) between satellites. If we compare this to the traditional counterpart, where one bit is sent one at a time that can be encoded with 1 (signal) and 0 (no signal), this seems to be enough.

However, quantum optics allows us to increase the alphabet and safely describe more complex systems, such as unique fingerprints or faces, in a single shot.

“Traditionally, two communicating parties would physically send messages from one to the other, even in the quantum realm,” said Professor Andrew Forbes, Chief PI at the University of the Witwatersrand.

“Now, it’s possible to send a message so that it doesn’t physically cross the connection—’Star Trek’ technology becomes a reality.” Unfortunately, teleportation has only been demonstrated in three dimensions so far (imagine a three-pixel image), so additional entangled photons are needed to reach higher dimensions.

In this study, the team conducted the first experimental demonstration of high-dimensional quantum transmission using two entangled photons as quantum resources, which resulted in a message seemingly being “transmitted” from the sender to the receiver. To make progress, the team used nonlinear optical detectors, which require no additional photons but are suitable for any “mode” that needs to be sent.

They report state-of-the-art technology in 15 dimensions that can be extended to higher dimensions, paving the way for quantum network connections with high information capacity.

Practical application in banking environment

Perhaps imagine a customer wanting to transfer sensitive information to a bank fingerprint. In traditional quantum communications, information must be sent from the customer entity to the bank, and there is always a risk of interception (even if it is secure). In the newly proposed quantum transmission scheme, the bank sends a single photon with no information (one of an entangled pair) to the client, who overlays it with the information to be sent on a nonlinear detector.

As a result, the message appears at the bank just as it was transmitted there. No messages are physically sent between the two parties, so interception is futile, and the quantum link connecting the two parties is established through the exchange of quantum entangled photons.

Forbes explains: “The protocol has all the hallmarks of teleportation, except for one basic element: It requires a bright laser beam to make the nonlinear detector efficient so that the sender can know what to send, but it doesn’t require Know.” .

“In that sense, it’s not strictly teleportation, but if nonlinear detectors can become more efficient, it could be teleportation in the future.” For now, it opens up a path New ways to connect quantum networks introduce nonlinear quantum optics as a resource.

“We hope that this experiment demonstrates the feasibility of this process, driving further progress in the field of nonlinear optics by pushing the limits of full quantum realization,” said Dr. Adam Valls from ICFO (Barcelona), who is the project leader one of the persons in charge. He conducted this experiment while working as a postdoc at Wits.

“We must be cautious now, as this configuration does not prevent a cheating sender from retaining a better copy of the message being transmitted, which means we may end up seeing many clones of Mr. Spock in the Star Trek universe. If this is Scotty wanted.”

“From a practical perspective, the configuration we have demonstrated so far can already be used to establish a high-dimensional secure channel for quantum communication between two parties, provided that the protocol does not require the input of a single photon, as is the case with quantum repeaters. “

Recognition of doctoral studies

Valls added: “It has been an interesting journey to conduct such a proof-of-concept experiment using existing technology, and we would like to thank Dr Bereneice Sephton at Wits for her determination and all-round skills required to tame such an experimental beast. It is truly She should be commended for her laboratory efforts.”

Forbes echoed the sentiment: “This was a heroic experiment, and Dr. Bereneice Sephton must be recognized as the person who made the system work and conducted the critical experiments.”

The team plans to continue working in this direction, with the next step focusing on quantum transmission over fiber optic networks.