Amazon and Harvard University created the «quantum network», which transmitted an entangled photon from one quantum computer to another through 35 kilometers of fiber optic cable.
The researchers placed a set of nodes around Boston to build a network capable of «efficiently catching, storing, and transmitting information that was originally stored in» light. Like the Internet as we know it, quantum networks send information carried by light — in this case, quantum entangled photons. But they need «repeaters» to prevent the photons from scattering over long distances, as light normally does. The repeaters must be able to send a photon without breaking its entanglement and without changing its information.
Harvard and Amazon AWS center they saythat the experimental nodes use cavities in diamonds that «trap light and force it to interact with quantum memory». These nodes can be mass-produced using existing technologies. During the experiments, the team took a qubit encoded into a photon and mirrored it from a quantum memory in a Harvard lab.
«When a photon interacts with a quantum memory, it becomes entangled in the memory, meaning that measurements made on either the photon or the memory will provide information and thus change each other’s state.
However, instead of measuring the photon (i.e., obtaining information), the photon undergoes a quantum transformation from the visible frequency (in which quantum memory operates) to the telecommunication frequency (where losses in the optical fiber are minimized). In this way, the photon travels back and forth through the underground fiber optic network before returning to Harvard, where it is converted back to visible frequency.
After completing this journey, the photon bounces off another quantum memory in another lab, thus transferring the photon’s entanglement to this second memory. Finally, the photon, after bouncing off the second memory, is sent to a detector, which notices the presence of the photon but does not reveal any of the underlying quantum information contained in the light. It is entangled with the memory — this means that the measurement of either the photon or the memory changes the state of each other. The photon is then converted from a visible frequency to a telecommunication frequency, which then bounces off to another lab, thus completing the journey».
The first experiments showed that the quantum entangled photon traveled more than 35 kilometers. The entangled photon was stored for more than a second, which, according to the company, is enough for light to travel more than 300,000 km and more than enough time to circle the world 7.5 times.
Quantum networks use the same principles as quantum computing, utilizing the quantum state of photons to transmit information. Experiments with quantum networks have been underway for some time, but no one has yet created a fully commercial version. Scientists say that many improvements are still needed before a quantum network becomes scalable and commercially viable. So far, it is slow and can only send one qubit at a time.
Source: The Verge
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