Quantum entanglement

• How Are Qubits Created and Entangled?
  Qubits are encoded in controllable physical systems, then entangled by interactions or gates; a Hadamard and CNOT give a standard example.
• What Is a Good QFT Text on Entanglement Entropy?
  For a first focused treatment of entanglement entropy in quantum field theory, start with Nishioka’s review, then follow a topic-specific reference.
• Can Quantum Entanglement Be Used for FTL Communication?
  Entanglement produces correlations across distance, but neither party can control the remote outcomes needed to send a faster-than-light message.
• Can a Local Operation Disentangle Two Parties?
  A local unitary cannot change bipartite entanglement, but a local measurement or noisy channel can destroy it. See the Bell-pair proof.
• How Does Pilot-Wave Theory Explain a Quantum Eraser?
  A quantum eraser is compatible with pilot-wave theory: entanglement hides fringes in the unsorted data, while postselected subsets reveal them.
• How to Distinguish Pure, Mixed, Entangled, and Separable States
  Use density-matrix purity to test pure versus mixed states, then apply entanglement criteria such as partial transpose or witnesses to bipartite states.
• Are Resonating Valence-Bond States Long-Range Entangled?
  RVB states are not all long-range entangled: some form topological spin liquids, while others are short-range entangled or critical.
• How Are Entanglement and the Pauli Exclusion Principle Related?
  Entanglement and Pauli exclusion are distinct: fermion antisymmetry restricts allowed states, while entanglement describes correlations within a state.
• How Is MPS Bond Dimension Related to Entanglement?
  An MPS bond of dimension D limits the Schmidt rank across its cut to D and the entanglement entropy to log D, but need not saturate either bound.
• Can a Digital Computer Simulate Quantum Entanglement to Any Precision?
  A classical digital computer can approximate entangled quantum systems to arbitrary precision in principle, but general simulations can require exponential resources.
• Are Electromagnetic Waves the Only Way to Transmit Information?
  No. Sound, mechanical motion, particles, and other physical signals can carry information; relativity limits causal signaling to at most light speed in vacuum.