Quantum computers,quantum cryptography, andquantum (insert name here)are often in the news these days.
Articles about them inevitably refer toentanglement, a property of quantum physics that makes all these magical devices possible.
Einstein called entanglement spooky action at a distance, a name that has stuck and becomeincreasingly popular.
Beyond just building betterquantum computers, understanding and harnessing entanglement is also useful in other ways.
Is there some way to understand this spooky phenomenon?
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Conservation lawsare some of the deepest and most pervasive concepts in all of physics.
This law underlies the workings of all of our machines, whether they are steam engines or electric cars.
Quantum addition
Picture yourself on a nice hike through the woods.
You finally decide to go right,wistfully wondering about the road not taken.
In a quantum world, you could have chosen both.
The states of quantum systems can be added together and subtracted from each other.
The word for such a combination of quantum states is asuperposition.
The odds of one outcome versus the other are easy to calculate (with agood physics bookat hand).
You and your friend separate the pair, taking one each.
You find that yours has 40 units of energy.
You would know this even if your friend never revealed any information to you.
Nothing spooky about it (once you realize this is just correlation, not causation).
But the quantum states of a pair of atoms can be more interesting.
This is anentangled stateof the two atoms.
Neither your atom, nor your friends, has a definite energy in this superposition.
You would know this even if your friend never revealed any information to you.
Nothing spooky about it.
