Bad Qubits — Learn Quantum by Doing

Multiple choice

According to McClean et al. (2018), in a barren plateau the gradient of the VQE cost with respect to a parameter has zero mean and a variance that shrinks how, as a function of the number of qubits n?

Polynomially, with variance ~ O(1/n^2)
It grows exponentially as O(4^n)
It stays constant, independent of n
Exponentially, with variance bounded by O(1/4^n)