Untangling quantum entanglement

Symmetrical encryption is far quicker and less resource-intense than public/private key encryption, but has the downside that the symmetrical key needs to be distributed among parties. For this reason, we use public/private key encryption to secure the transfer of the symmetrical key, and then use symmetrical encryption to secure the actual data that needs to be transferred. But what if our symmetrical key was somehow available to the other party without us transmitting it to them? That could make the encryption process faster, less resource-intense and safer.

This is potentially possible at a quantum level where conventional principles of physics don’t apply. I’ve written before about the weird stuff that happens in the twilight zone of quantum physics. Recently, Darpa-funded scientists in Canada and China conducted independent experiments in quantum entanglement, and both teams successfully managed to teleport the state of a photon to its distant entangled photon.

In Star Trek episodes, Captain Kirk gave the command “Beam me up Scotty” to teleport physical matter (a person) from one place to another. Quantum entanglement is different as no physical matter actually changes location. Rather, changes in the characteristics of one particle causes the same change in the characteristic of its entangled particle positioned at another location. Once entangled, it is as if two particles are not individual, independent particles but are an inseparable whole, even with large distance separating them. One analogy is of identical twins experiencing each other’s pains, such as this report of one twin experiencing morning sickness when the other twin became pregnant.

Quantum entanglement is the phenomenon of particles or groups of particles that are paired or “twinned” and act in concert. If two photons are entangled and have state represented by 0, then even when separated by a large distance, if action is made changing the state of one of the photons from 0 to 1, the state of its paired particle instantly changes. A complicating factor is that at the quantum level, observing or measuring a particle causes it to immediately behave differently. Observation or measurement of one of a pair of entangled particles causes an almost instantaneous change in its paired particle – a hundred times faster even than the speed of light covering the distance between them. This further illustrates that nothing is actually transmitted between the particles because nothing is able to travel faster than the speed of light.

Even Albert Einstein was a bit perplexed by this and described the entanglement phenomenon as “spooky action at a distance”.

It is easy to see how entanglement can potentially be useful such as for communicating a symmetrical key over a distance without having to transmit any data. There is no distance limit over which particles remain entangled. However, as entanglement relies on the particle not being measured or observed, distance limitations apply when information relating to the initial state or changed state of the particle is relayed between the communicating parties.

In addition to exchanging symmetrical keys, there are many other potential real-world applications of the need to quickly and securely exchange data without actually transmitting. In the book Flash Boys, Michael Lewis described how traders who could transmit data faster than their competitors made a huge amount of money (through a process of front-running stock orders placed with them). A few milliseconds advantage would give a stock trader an enormous advantage. Even though there are still major hurdles to overcome, such as figuring out how to change a particle or establish whether a particle has changed or not, the latest Darpa research highlights the exciting potential for quantum entanglement as part of a process really fast and secure data communication.

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