What are the fundamental principles of quantum entanglement, and how do they challenge our classical understanding of causality and locality in physics?

Quantum entanglement is a phenomenon where two or more particles become interconnected in such a way that the state of one particle instantaneously influences the state of the other, no matter the distance separating them. This challenges classical physics in two significant ways:

**Challenges to Classical Causality**:
– **Instantaneous State Correlation**: In classical physics, causality implies that an effect cannot occur before its cause, and there is a limit to how fast information can travel (the speed of light). However, in quantum entanglement, the measurement of one particle’s state instantaneously determines the state of its entangled partner, seemingly defying this limit¹.

**Challenges to Locality**:
– **Non-local Interactions**: Locality in classical physics states that objects are only directly influenced by their immediate surroundings. Entanglement suggests that particles can have direct influences on each other regardless of the space between them, which Einstein famously referred to as “spooky action at a distance”².

These principles of quantum entanglement have been experimentally confirmed and are integral to the development of quantum computing and cryptography, further solidifying the non-classical nature of quantum mechanics⁶.