Bad Qubits — Learn Quantum by Doing

Multiple choice

The lesson says a classical signal lost in fibre can be re-amplified by repeaters, but an unknown qubit cannot be amplified the same way. Which principle forbids this amplification?

The second law of thermodynamics
The Heisenberg uncertainty principle for position and momentum
The no-cloning theorem, which forbids copying an unknown quantum state
The Pauli exclusion principle