title: measuring a quantum state of many-body quantum systems in computational basis
body: <p>I would like to measure a quantum state consisted of a large number of spins (around 300 spins) in computational basis.
  So, the simplest way to do that is to find all the spin configurations in computational basis and find the squared inner product of each possible configuration and the quantum state to find the probability.</p>
  <p>However, it requires large memory and takes long time.
  Would you please let me know if there is any approach to do it faster.
  Thanks</p>