An important mechanism within the quantum world is that of entanglement. Entanglement and superposition are linked and the terms can often become confusing so here I delineate what is meant by the term “Quantum Entanglement”. This will provide a base understanding of the mechanism, later easing the description of things like macro-entanglement and quantum computing.
So, entanglement in this context means that two particles such as electrons can become linked through a number of ways which allows them both to behave in ways not explained by classical physics. This is a good starting step, but how do we entangle electrons, atoms or whole molecules? And what about them is different when entangled?
Recall the principle of superposition; the position and momentum of either the trapped cat or the electron through two slits is uncertain, almost entirely unknowable until observed. Upon observation the state of the system is now forced into becoming a fixed particle. Well, while superposition describes a particle interfering with itself, entanglement plays on the uncertainty of two particles in a system.
Say, for example, that an isotope decays the mass of a proton. That mass must be made up by either an up and two down quarks or two up and one down quark. The particles have been expelled in different directions and all you can currently tell is the remaining mass of the isotope. So, the certainty of the particles is somewhat in superposition or entanglement because upon detecting one of the decayed quarks and discovering it is an up quark, it provides you the necessary information to conclude that the other is a down quark. This is usually used to argue that this demonstrates a violation of the universal constant, lightspeed, by happening faster than light could travel the distance, but there is much debate in the literature about this statement and whether the information gleamed about one particle from measuring another has any real bearing on physical phenomena.
At any rate, the above example is incredibly similar to superposition, only applying another layer to the uncertainty. Each quark can be said to be in superposition with itself; if one was propelled left and the other right, then until measurement, the left one is in a superposition state in which it could be either up or down and similarly with the right. They are entangled because breaking the superposition of one also breaks the superposition of the other, forcing it into a measured state with certainty.
This is the general principle of Quantum Entanglement, but there remains the questions of how we induce or detect entangled particles as well as what applications this has for computing and our understanding of the universe. It is thought that the key to inducing entanglement is the atomic spin of the two given particles, though there continues to be debate and informative research evidencing billions of electrons entangled at once during near-absolute-zero temperature phase transitions of strange metallic compounds – this example indicated alignement of electric charge and spin plays a significant roll in entanglement.
At present, it’s difficult to produce entanglement in the warm, noisy conditions on Earth but the cooler conditions of empty space, or labs where systems can be cooled to near 0°Kelvin are ideal for developing controllable examples of entanglement. Over time the temperature, materials and scenarios in which entanglement can be produced will become more accessible, paving the way for much much smaller technology and incredibly advanced computing capabilities.
The relevance and importance of entanglement in computing technology will be explored in my upcoming paper on the Quantum Internet so stay tuned for that. Also, evidence suggests the brain is able to produce, activate, entangle and measure unperturbed quantum states within it’s very warm and noisy neuronal system, something we cannot do in the lab – some suggest that conscious brains are a topological state of matter of their own! To find out more, check back on my upcoming article on Quantum Consciousness to the nth degree for more intriguing explorations of seldom understood phenomena.