Quantum entanglement is the second foundational resource — alongside superposition — that enables quantum computing to outperform classical systems on certain problems. When qubits are entangled, measuring one instantly determines the state of its partner, regardless of the physical distance between them. Einstein famously called this "spooky action at a distance." In a quantum computer, entanglement allows qubits to share information in ways that have no classical analog, enabling algorithms to explore solution spaces with far fewer operations than classical alternatives.
Creating and maintaining entanglement between qubits is essential for quantum computation. Two-qubit gates (like the CNOT or CZ gate) generate entanglement between qubit pairs, and multi-qubit entangled states are the backbone of quantum error correction codes. The quality of entanglement — measured by gate fidelity — is a key performance metric. IBM, Google, and Quantinuum regularly benchmark their systems on how reliably they can create entangled states, with current two-qubit gate fidelities exceeding 99% in leading platforms.
Beyond computing, entanglement has applications in quantum communication and quantum networking. Entanglement-based quantum key distribution provides theoretically unbreakable encryption. Quantum repeater networks, being developed by companies like Aliro Quantum and PsiQuantum, aim to distribute entanglement over long distances to create a quantum internet. The ability to generate, distribute, and preserve entanglement at scale is one of the defining engineering challenges of the quantum technology era. For deeper coverage, see DeepTechIntel's quantum computing section.