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Physics + MathPhysics & Math

Crystal-Powered Quantum Entanglement Satellite Will Test Quantum Communications

ByJulia DavisNOVA NextNOVA Next

The world’s first satellite equipped to do quantum experiments is about to head into orbit. In August, China will launch its 600-kilogram, $100-million spacecraft, and hopefully advance our future understanding of quantum mechanics.

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If this first trial is successful, an entire fleet of quantum-enabled satellites is likely next.

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Quantum Encryption
Encryption technology is used to achieve data security. To read encrypted files, users must have access to a secret key or passcode used to decrypt the information.

The satellites will create a communications network which is quantum-encrypted, making it extremely secure, and this network could be used to potentially link people anywhere in the world.

But China is not the only country with quantum space experiments in the works. Groups from Canada, Japan, Italy, and Singapore are in the planning stages of theirs, creating a quantum space race of sorts.

Quantum mechanics boosts cryptography to a new level that modern cryptography would not be able to compete with. The reason has to do with the infinitesimal size of quantum particles, which means any disruption to them is noticeable.

Here’s Elizabeth Gibney, reporting with Nature :

Quantum communications are secure because any tinkering with them is detectable. Two parties can communicate secretly — by sharing a encryption key encoded in the polarization of a string of photons, say — safe in the knowledge that any eavesdropping would leave its mark.

So far, scientists have managed to demonstrate quantum communication up to about 300 kilometers. Photons traveling through optical fibers and the air get scattered or absorbed, and amplifying a signal while preserving a photon’s fragile quantum state is extremely difficult. The Chinese researchers hope that transmitting photons through space, where they travel more smoothly, will allow them to communicate over greater distances.

The photons used in the satellite will be created in pairs from a crystal onboard. The pairs of photons produced will be interconnected, causing the properties of the photons to remain entwined no matter how far apart they are.

After this initial creation, the first step to securing encrypted communication will be for the satellite to fire off a pair of these entwined photons to ground stations in Beijing and Vienna so they can generate a secret key.

Along with creating quantum communication, the Chinese team will try to “teleport” quantum states by shooting a pair of entangled photons down to Earth alongside information transmitted using more conventional methods. The idea is to use this information to reconstruct the quantum state of a photon in a completely new location.

In order to China to support secure communications throughout the world, they would need to place about 20 of these satellites into orbit.

The satellites may be a step in the development of a “quantum internet” comprised of quantum computers around the world sharing data across a combination of satellite and ground-based links.

But before this can happen, physicists will need ensure that the satellites can reliably communicate with each other directly. There are other hurdles, too, not least of which is improving the data transmission rate by tenfold. Currently, the system can transmit megabits per second, but to be useful, it’ll need to send gigabits per second.

If the Chinese team can get it to work, though, it could usher in a new era of encrypted communications.

Photo credit: / Flickr (CC BY-NC-ND 2.0)

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