Science

Quantum entanglement isn't only spooky, you can't avoid it

Quantum entanglement isn't onl...
Entanglement mixes you with everything (Photo: ShutterStock)
Entanglement mixes you with everything (Photo: ShutterStock)
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Two ions are being entangled using microwaves in this NIST apparatus (Photo: Y. Colombe/NIST)
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Two ions are being entangled using microwaves in this NIST apparatus (Photo: Y. Colombe/NIST)
Delayed EPR entanglement of two quantum images (Photo: A. Marino/JQI/NIST)
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Delayed EPR entanglement of two quantum images (Photo: A. Marino/JQI/NIST)
Entanglement mixes you with everything (Photo: ShutterStock)
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Entanglement mixes you with everything (Photo: ShutterStock)

Quantum entanglement is the key to quantum computing, cryptography, and numerous other real-world applications of quantum mechanics. It is also one of the strangest phenomena in the Universe, overcoming barriers of space and time and knitting the entire cosmos into an integrated whole. Scientists have long thought that entanglement between two particles was a rare and fleeting phenomenon, so delicate that exposure of the particles to their surroundings would quickly destroy this linkage. Now mathematicians at Case Western University have shown that entanglement between parts of large systems is the norm, rather than being a rare and short-lived relationship.

Entanglement is one of the strangest predictions of quantum mechanics. Two objects are entangled if their physical properties are undefined but correlated, even when the two objects are separated by a large distance. No mechanism for entanglement is known, but so far experiments universally show that nonlocal entanglement is real. When two entangled particles are subjected to the influence of a surrounding environment, their interactions with the surroundings cause the entanglement to "leak out" into the surroundings, so it is more difficult to detect and use, but it does not disappear.

Entanglement is clearly subtle, but how common is it in the real world of macroscopic objects? A new research paper from Professor Stanislaw Szarek's mathematics group at Case Western Reserve University addresses this question, and finds that entanglement is ubiquitous in large objects.

Their analysis is essentially statistical, where the quantum probabilities are studied using the tools of geometric functional analysis, a field of mathematics well suited for addressing problems associated with very large numbers of dimensions.

Systems of a few particles will tend to lie close to a pure state, a state in which none of the internal particles are entangled with each other. The particles of such a system will show essentially no sign of being entangled. You can create a state of a few particles in which the particles are entangled, but these states are quite unusual.

When you consider larger systems, perhaps having thousands (or trillions) of particles, the quantum description is essentially the same, but the way the quantum attributes of the system scale with size changes the probabilities considerably. Now the pure states form only a very small portion of the possible quantum states, and as a result, the more probable behavior is that parts of the system are entangled with each other.

Szarek's team also considered the entanglement of subsystems of an entangled system. If you choose two particles from a system, the chance that they are entangled is very small; in fact, vanishingly small in the limit of very large systems. On the other hand, if you split the system in two, these halves are almost certain to be entangled with each other.

In the end, their analysis shows that in systems having large numbers of particles, a pair of tiny subsystems tend not to be entangled with each other, but a pair of large subsystems tend to be entangled. If you consider two subsystems each having fewer than about one-fifth of the total number of particles in the overall system, the subsystems are almost certainly not entangled with each other. If the two subsystems are larger than one-fifth of the original system, they are almost certainly entangled. The abrupt change in entanglement behavior is characteristic of the geometry of high-dimensional spaces.

The result shows that everyday objects are so constructed that their parts are entangled with each other, and are also entangled with most everything with which they have previously interacted. This is an interesting result, particularly for those who think of the Universe in holistic terms, but does this holism have any observable consequences? This is a very difficult question, to which we don't yet have a practical answer.

Large-scale entanglement guides how our world evolves, often in crucial ways. However, predicting how a specific action might change that evolution appears impossible, at least in any practical sense. Such prediction simply requires too much knowledge about the microscopic state of the world. One might say, facetiously, that magic works, but usually has no real and/or predictable effect. At least, within quantum mechanics.

Sources: Case Western Reserve University, arXiv.

20 comments
Riaanh
Fascinating! I can't help to wonder about its influence on things like identical twins having a special connection, i.e. the one being in an accident and the other one feeling something at the same time. Who knows?
DomainRider
@Riaanh - it seems very unlikely that entanglement has anything to do with any 'special connection' between twins such as you suggest, as it cannot be used to transfer information. It might be said that any entanglement between twins would be special *because* it would have no influence on either.
notarichman
so, if the internet is split such as .gov and .com and each subsystem has at least 1/5 of the total; then they are entangled? If you consider large enough systems; then they have a chance of being entangled, though not split apart? i probably got this question wrong... but consider using this entanglement as a way of viewing what is going on at another planet or solar system or galaxy. what defines the terms: "system", "split", "subsystem"? Does .gov and .com mean that they have split off the internet "system"? If another internet forms that has never been connected to the present internet and is at least 1/5 in size; then does that mean they are entangled? or do they have to be "split off"? Given NSA's current prism program, imagine the consequences of spying between internet subsystems, etc. I would think that twins would be considered a split of at least 1/5, but how do we know that they were part of a "system"? What is the lower limitation of the size of a system? what if the original system before being split grows? If a meteorite comes from the asteroid belt; then could we use it to view the asteroid belt from close up? I can't see how the asteroid belt could be considered a split off of a system, let alone the meteorite be considered 1/5 of the total...so the next question is how do we make an entanglement occur without the original system and or size? that would seem to make quantum entanglement actually useful.
Grumpyrelic
Hmm... build a ship that rides the entanglement and you could be everywhere at once all the time. Sounds like a description of god doesn't it? I wonder what sort of person we could meet there...
Mihai Pruna
this would explain several previously unexplained phenomena related to telepathy premonitions ghosts and you name it
Stephen Funck
Sounds like God omnipresent, omnipotent, omniscient from before the beginning to after the end Alpha and Omega unknowable dimensions, outside of time real, hidden, revealed divine paradox
see3d
If large systems that have interacted with each other are certainly entangled, then how about the big bang? Everything in this universe is then entangled no matter how far apart today.
Pecos Pete
This was a theme in Red Dwarf X episode 4 by Doug Naylor!
bdodson
see3d, Good insight. check out http://arxiv.org/pdf/1205.1584.pdf. Brian Dodson
Tickoslav Damien Tockovich
Humans already have long empirical relationship with Quantum Entanglement in large systems; it has been called sympathetic magic. :)