Bell states are a special set of maximally entangled states involving two qubits. They represent the strongest form of quantum correlation where the state of one qubit instantly determines the state of the other, no matter the distance between them.
The Four Bell States:
They form a complete orthonormal basis for two-qubit systems, commonly written as:
- Φ⁺ = (|00⟩ + |11⟩)/√2
- Φ⁻ = (|00⟩ − |11⟩)/√2
- Ψ⁺ = (|01⟩ + |10⟩)/√2
- Ψ⁻ = (|01⟩ − |10⟩)/√2
Key Features:
- Each Bell state is maximally entangled—measurement outcomes on one qubit perfectly predict outcomes on the other.
- Exhibits nonlocal correlations that violate classical physics limits (Bell inequalities).
- Serves as fundamental resources in quantum communication and quantum computing.
Applications:
- Quantum teleportation: Transferring quantum states using entanglement.
- Superdense coding: Sending two classical bits via one qubit.
- Quantum cryptography: Ensuring secure communication.
Bell states are central to understanding and harnessing the power of quantum entanglement in advanced quantum technologies.