Quantum mechanics, also called quantum physics and quantum theory, is the branch of science responsible for explaining how nature works at the subatomic level. Though it is incompatible with the Theory of Relativity, which explains the relationships between space-time, matter, energy, and gravity, quantum mechanics is the most successful theory humans have of how the subatomic universe functions.
The most mysterious and least understood principle of quantum mechanics is a phenomenon called quantum entanglement. Quantum entanglement involves two particles that are linked, so when the state of one particle is measured, the state of the other changes. The change occurs instantaneously, no matter how far apart the particles are from each other in space, even if they are at opposite ends of the Universe. This seems to defy the very basic laws of physics, which state that nothing can travel faster than light.
Albert Einstein referred to quantum entanglement as “spooky action at a distance,” and it bothered him greatly. Furthermore, the state of either particle, or “spin,” is not determined until the particle is observed. This strange behavior is known as non-locality, and it implies that reality does not exist until it is observed. These concepts are mind-bending and will be discussed later in this piece. But they have real-world applications with which scientists are experimenting.
One such application is quantum teleportation, which is the transfer of information between entangled particles. Particles, such as photons, become entangled when a beam of light is split by a prism. Each photon automatically carries the opposite polarization, or “spin,” of the other, due to the law of conservation of momentum. Quantum teleportation, though still in its experimental infancy, has the potential to provide secure, unhackable cyber-security and communication. Seemingly stolen from an episode of ‘Star Trek,’ physicists have for the first time sent information between entangled particles under water.
In an experiment at Shanghai Jiao Tong University, Professor Xianmin Jin and his team of physicists filled a 3-meter long tank with seawater collected from the Yellow Sea. The team shot a beam of light through a crystal, creating a pair of entangled photons. The pair of photons were fired into opposite ends of the tank, where their quantum link, and related spins, were maintained 98 percent of the time. Because water scatters light, and photons are particles of light, this is a significant achievement. The team estimates that with current capability, communication between entangled photons could occur at a distance up to 900 meters. Underwater quantum teleportation has the potential to provide secure communication channels. For example, submarines in the future could send secure information without having to surface, using seawater as an additional layer of security. The limited distance quantum information can be sent underwater, however, represents a challenge for this technology to ever have a practical application.
The first successful test of quantum teleportation outside of a lab occurred in 2016. Independent teams in Calgary, Canada and Hefei, China, successfully transmitted quantum information across more than 7 kilometers of a fiber optic network. Though limited to only 17 photons of information per minute, the experiments proved that it is indeed possible to send naturally-encrypted, unhackable information without the information having to travel through physical space. Because quantum information does not need to travel through space, it cannot be hacked or intercepted. The only way to retrieve a message is a unique key at either end of the transmission. This is due to the very nature of quantum entanglement; if a hacker were to attempt to intercept either entangled photon, the state of each would reverse, instantly, preventing any outside interference.
Indeed, this is very complex and strange stuff. To understand why this type of communication is possible in the first place, we must challenge our very perception of reality.
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