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.
But let see what happens if we use capital letter A (A for ARTICHOKISTAN )
This demonstrates, as expected, the reduced density matrix for an entangled pure ensemble is a mixed ensemble.
Clear, isn't it?
To make it more clear, see my drawing ;)
Have a nice day !