Bad Qubits — Learn Quantum by Doing

Multiple choice

Distributing a Bell pair directly over fibre has cost growing exponentially with distance L. By splitting the span into short elementary links and using nested entanglement swapping, a quantum repeater changes the cost to grow how with L?

Still exponentially in L, just with a smaller base
Only polynomially in L (with polylogarithmic overhead)
Independently of L, at constant cost
Logarithmically in L, beating any polynomial