Bad Qubits — Learn Quantum by Doing

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Multiple choice

A quantum state obeys an 'area law' for entanglement entropy when, for a cut-out region A, the entropy S(A) scales with which feature of A?

The number of qubits in the volume of A (S(A) ~ length of A)
The square of the number of qubits inside A
The size of the boundary of A (the surface separating it from the rest)
The total number of qubits in the entire system, regardless of A