Amazon and Harvard University have developed an innovative “quantum network” that has managed to transmit an entangled photon between two quantum computers through 35 kilometers of optical fiber cable. This milestone represents a substantial step towards the future of quantum communication, which promises ultra-secure and efficient data transmission.
The team of researchers from the Amazon Web Services Center for Quantum Networking and Harvard installed a set of nodes around the city of Boston (Massachusetts) to create a network capable of capturing, storing, and transferring information initially stored in light. Unlike conventional Internet, which transmits data using light, quantum networks use quantum entangled photons. However, to prevent photons from dispersing over long distances, special repeaters are necessary to maintain entanglement without altering the information.
In their research, Harvard and AWS used experimental nodes with diamond cavities that “trap light and force it to interact with quantum memories”, manufactured with existing nanofabrication technology. During the experiments, a qubit encoded in a photon was sent to a quantum memory in a Harvard laboratory. When the photon interacted with the memory, they became entangled, allowing measurements made on one to affect the other.
In order to minimize losses during transmission through optical fiber, the photon underwent a quantum frequency conversion, transitioning from a visible frequency to a telecommunications frequency. The photon traveled through the underground fiber network, returned to Harvard, and was reconverted to its original frequency. Afterwards, the photon interacted with another quantum memory in a different laboratory, transferring entanglement and allowing the photon, after bouncing off the second memory, to be detected without revealing the underlying quantum information.
The initial experiments showed that the quantum entangled photon traveled more than 35 kilometers and was stored for more than one second, enough time for light to travel over 300,000 kilometers. However, AWS has indicated that the network still needs significant improvements before being commercially viable, as it is currently slow and can only send one quantum memory at a time.
