Satellite sends First Quantum Signal to Earth

• An orbiting satellite has sent the first entangled pair of photons to Earth
• It is a big step towards achieving a secure and developed way to encrypt communications
• They can not be cracked by ever-improving computer algorithms

June 18, 2017: It was reported by scientists today that an orbiting satellite has sent the first entangled pair of photons to Earth. It is a big step towards sending quantum keys from satellites — an approach that has been heralded as a secure and developed way to encrypt communications because ever-improving computer algorithms can not crack them.

A laser on China's Micius satellite, which was launched last year and is dedicated to researches related to quantum satellite communications, spit out pairs of entangled photons from its position, 500 km above Earth. Then two telescopes on Earth – about 1200 km apart — had 5 minutes each day to look for them as the satellite passed over both telescopes. It was found that paired photons survived the journey through Earth's atmosphere. They detected 1 entangled pair per second out of the 6 million sent in that time.

So how exactly does all this work?

A quantum key needs to be generated first by two people who are looking to communicate. Then, one person receives one of the entangled photons in the pair, the other person receives the other. When the received photons have measured the photons, they obtain bits of information strung together to create a key that they both have. That key can be used to encrypt and decrypt a message. The users can also share a portion of the key publicly to check if it has been compromised. In case if someone tries to intercept the communication at any point, they would then notice a difference between their strings.

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There is a certain set of problems as well. Caltech's John Preskill believes even though it is an important proof of concept, the feat doesn't address one of the biggest problems with quantum communications. Currently, these messages can't be sent long distances. Photons, using an optical fiber to carry a quantum signal, can only make it about 100 km before the dissipation of the light.

Quantum systems are similar to optical telecommunications here on earth and need repeaters that are able to amplify the message so it can be passed long distances. But amplifying a quantum message in the same way optical ones are done would effectively result in the destruction of the information. That is why satellite-based communication are being eyed by researchers. The reported 500 km from space is an improvement over optical. Quantum signals were measured in another study published today from a satellite 38,000 km away to a single point. But in deploying a global network which would likely be able to combine optical fiber and satellites, the repeater problem still stands.

Preskill has predicted that it is more likely we will first come up with another form of encryption for communication. "There will be other ways of doing classical public key cryptosystems that we won't know how to break with quantum computers," he added.

– prepared by Durba Mandal of NewsGram. Twitter: @dubumerang