In a groundbreaking experiment, researchers have successfully transmitted a quantum signal with multiple bits per photon through the air. The manipulated photon was sent over a distance of 300 meters above the rooftops of the city of Ottawa, Canada. Quantum communication is believed to be the future, especially in the field of quantum cryptography, which is considered almost unhackable. The advantage of this communication technology is that signals can reach the receiver almost in real-time, even over long distances and between Earth and orbit. Until now, only one bit per photon was transmitted, but by manipulating multiple properties of the photon, multiple bits can be transmitted.
Ebrahim Karimi and his colleagues from the University of Ottawa successfully sent a manipulated photon and read it again at a distance of 300 meters. They installed their laboratory instruments, which generate entangled photons, on rooftops in the city of Ottawa. They manipulated the quantum states so that each photon can transport two bits, or four possible signals: 00, 01, 10, or 11. This process is also known as 4D quantum cryptography. The researchers wanted to find out if the quantum information could survive the transport through the city of Ottawa, where the state of entanglement is very susceptible to disturbances.
Despite the challenges, the researchers were able to successfully send messages using high-dimensional quantum encryption under real city conditions. The error rate was only 11%, which is significantly lower than the 19% threshold for secure transmission. This experiment is a significant step forward in the field of quantum communication and cryptography, and it opens up new possibilities for secure communication over long distances.
