Scientists develop new method for high-speed, secure quantum communication

(a) The experimentally retrieved (upper row) and theoretically predicted (lower row) density matrices of two selected quantum states. (b) Theoretically (left panel) and experimentally retrieved (right panel) probability-of-detection matrix. Credit: Chinese Academy of Sciences.

Scientists have made a major breakthrough in quantum communication by creating a new method to transmit information using particles of light called qudits.

This advancement promises a future quantum internet that is both secure and powerful.

The study was published in the journal eLight.

Quantum information is usually encoded on qubits, which can be in a state of 0, 1, or both at the same time (a property called superposition).

While qubits are great for complex calculations, they have limitations in the amount of data they can carry. Qudits, on the other hand, can encode information in more dimensions, allowing them to transmit more data in one go.

The new technique uses two properties of light—spatial mode and polarization—to create four-dimensional qudits.

These qudits are built on a special chip that allows for precise manipulation, leading to faster data transfer rates and fewer errors compared to traditional methods.

One key advantage of qudits is their ability to maintain their quantum properties over long distances.

This makes them ideal for applications like satellite-based quantum communication, where data needs to travel far without losing its integrity.

The process begins by generating a special entangled state with two photons. Entanglement is a phenomenon where two particles become linked, sharing the same fate no matter how far apart they are.

In this method, one photon (the signal photon) is manipulated on the chip to create a 4D qudit using its spatial mode and polarization.

The other photon (the idler photon) remains unchanged and acts as a remote control for the signal photon. By manipulating the idler photon, scientists can control the state of the signal photon and encode information onto it.

This new method could revolutionize quantum communication, paving the way for a high-speed quantum internet that can securely transmit large amounts of data over long distances.

It also has the potential to develop unbreakable encryption protocols and contribute to the creation of powerful quantum computers that can solve problems beyond the reach of classical computers.

Researchers are now focused on improving the accuracy of the qudits and scaling up the technology to handle even higher dimensions, bringing us closer to a secure and powerful quantum future.