Schrödinger’s anthill: Quantum entanglement found in a crystal large enough to hold - Science Daily

Quantum entanglement captures one of the strangest differences between everyday physics and the quantum world. In an entangled system, particles such as photons become linked so deeply that their properties cannot be fully described independently. Instead, the system must be treated as a whole. That idea clashes with the classical expectation that each particle should possess its own separate physical reality, a feature of quantum mechanics that famously troubled Albert Einstein. Yet entanglement is now considered one of the essential ingredients for emerging quantum technologies, including advanced communication, computing, and information transfer.

At some point between the tiny world of particles and atoms and the much larger world we experience every day, quantum behavior appears to fade away. Quantum mechanics allows particles to exist in combinations of possible states, a phenomenon known as superposition. That strange feature inspired Schrödinger's famous thought experiment involving a cat that is both alive and dead until it is observed. Yet objects in the everyday world do not behave that way.