Category: quantum entanglement

No, We Still Can’t Use Quantum Entanglement To Communicate Faster Than Light

“There’s an awful lot that you can do by leveraging the bizarre physics of quantum entanglement, such as by creating a quantum lock-and-key system that’s virtually unbreakable with purely classical computations. But the fact that you cannot copy or clone a quantum state — as the act of merely reading the state fundamentally changes it — is the nail-in-the-coffin of any workable scheme to achieve faster-than-light communication with quantum entanglement.

There are a lot of subtleties associated with how quantum entanglement actually works in practice, but the key takeaway is this: there is no measurement procedure you can undertake to force a particular outcome while maintaining the entanglement between particles. The result of any quantum measurement is unavoidably random, negating this possibility. As it turns out, God really does play dice with the Universe, and that’s a good thing. No information can be sent faster-than-light, allowing causality to still be maintained for our Universe.”

You might think that if you have two entangled quantum particles, you can separate them by a large distance, make an observation of some physical property at one location, measure your member of the entangled pair, and use that existing entanglement to send information about what you observed instantaneously to anywhere in the Universe. It’s a brilliant and clever idea, and it turns out it’s absolutely forbidden by the laws of physics.

What’s really going on with quantum entanglement, and why can’t it send information faster than light? Find out today.

Quantum entanglement is undoubtedly an extremely interesting topic of quantum mechanics; not only because it is just unbelievable moreover it is the fundament of new technological applications such as quantum communication.

A group of Chinese physicists (especially Jian-Wei Pan) were able to show that quantum entanglement even works when a satellite sends two entangled photons to two ground stations which are 1200 km apart. The used satellite is called Micius and travels with a distance of 500 km around the earth. Until then comparable experiments only suceeded with distances of approximately 150 km like the experiment of the austrian physicist Anton Zeilinger who sent entangled photons from La Palma to Tenerife.
The significantly innovative idea of the new experiment is that they send the photons through the vacuum of space. Consequently distractions because of the atmosphere occur less.
On the other side of the coin running this experiment in space leads to several obstacles: The devices inside Micius must be able to resist the strong temperature differences between day and night. Furthermore they have to endure the strong vibrations of the launch. Moreover the two mirrors which direct the photons to the ground stations have to be more exact as these of usual satellites because the two entangled particles have to hit the 1,2m x 1,8m mirrors on earth.
Although this experiment is a great step for developing safe quantum communication the usage for technological applications seems to be far in the future. Because of the distracting sun light it can only be performed at night. Besides only one bit per second can be transmitted with this method at the moment. But there is still space for hope: The leading scientist Jian-Wei Pan thinks that “the data rate will rise by a factor of 100 in the next five years”.


source: http://www.spektrum.de/news/verschraenkte-photonen-aus-dem-all/1464637