A newly created system can improve quantum communication over longer distances – a small but crucial step towards one Quantum internet.
We are in the early stages of a quantum boom as researchers try to expand our computing and communication skills with systems that use the strange math that controls subatomic particles. One of the main goals of this era are networks that can transmit quantum information over longer periods of time, which scientists believe could lead to advances in cryptography, acquisition, or even distributed quantum communication. But these are mostly dreams; Such a network cannot really exist without components such as repeaters to extend the distance that quantum information can travel, or transducers that can convert quantum information into transferable photons. This new paper brings the field of invention of a quantum repeater closer.
"Classic repeater stations measure this signal and amplify a copy of it", Harvard physics graduate student Mihir Bhaskar told Gizmodo. “This is how all information reaches the whole world. When building a quantum network, we try to do something similar, but we communicate with individual photons. “
Today our networks send information encoded as bits. However, certain natural systems such as photons (light particles) or the electrons orbiting atoms can store a larger amount of information in their properties. More importantly, these systems can get tangled, so repeated measurements at distant points are more correlated than the regular probability would otherwise allow. Quantum information scientists believe that one day they will be able to use networks that use these attributes to send non-hackable messages, improve the capabilities of sensors, or perform tasks that have not even been conceived.
One of the key challenges is how difficult it is to send quantum information over long distances. This information is encoded in individual photons that can be lost over a few kilometers of fiber optic cable. Any network hoping to connect nodes further apart than a city would need a repeater to amplify the signal from point A and relay it to point B . H however, is an additional challenge and, unlike a regular repeater, it is impossible to restore an exact copy of a quantum state because measuring a quantum state destroys it.
A team from Harvard and MIT has developed a central node that effectively halves the distance a message must travel. The system which is kept in a dilution refrigerator at almost absolute zero Kelvin consists of a diameter with one of replacing two carbon atoms with a single one Silicon dioxide on the atom, which creates a region in which the quantum state injected by a photon can be temporarily stored in an ultra-cold dilution refrigerator.
The system receives an incoming photon from point A, then saves the state of the photon ( without destroying it ) l enough to hold a photon from Receive point B After synchronizing and entangling these photons, the central node generates a secure key that correlates between the two parties, which is only important for the two messengers. With this key you can then encrypt and decrypt messages between them.
The researchers published their study in the journal Nature.
This is not a repeater that forwards quantum information directly from point A to point B, explained Bhaskar. But it is an important missing ingredient to get to this point at some point – an intermediate interface between quantum information stored as light and a node in the middle. They are working to demonstrate that they can send a message from point A to node and then to point B, or even extend the range by placing more of these Diamond units between two knots.
Many more improvements are needed before this device can become part of long-distance quantum communication. It has to be implemented between two really independent independent parties, not just between stations in a laboratory. In addition it is currently operating on a different wavelength than that which is best today for use over fiber optic cables, and requires a means to convert signals into these wavelengths.
Other researchers who were not involved The study praised the technical performance of the work. Barry Sanders, director of the University of Calgary's Institute of Quantum Science and Technology, told Gizmodo that it was "an exciting demonstration of the principle," not only for the way it demonstrated quantum memory, but was taking measurements, to confirm the interconnection between the photons. However, scaling for more practical purposes is still a long way off.
Another researcher, Prem Kumar, director of the Center for Photonic Communication and Data Processing at Northwestern University (also not involved in the study) agreed. It was a remarkable job and a crucial step – if only one of many necessary steps – towards a possible quantum repeater. However, he emphasized that a full-fledged quantum network is far from possible.
Scientists around the world are working on various aspects of a possible quantum internet. Researchers have designed fiber optic lines in the Chicago and Boston regions to do more experiments like this over over shorter distances. China's quantum efforts, led by Jian-Wei Pan from the University of Science and Technology in China, have managed to entangle quantum states over 50 kilometers of wire in the laboratory and entangle photons from laboratories around the world with the Micius Satellite as an intermediary . However, these are all just pieces of a much larger puzzle that need to be integrated together while overcoming other problems – such as the aforementioned converters, which have to translate quantum information stored in a quantum processor into photons that move across a fiber  This is an advance to be pleased about, but as Kumar Gizmodo said, it is only a few meters to the nebulous quantum internet of the future.