Returns the probability of getting a one measurement on a state shard.

def _one_prob_per_shard(args: Dict[str, Any]) -> float:
    """Returns the probability of getting a one measurement on a state shard.
    """
    index = args['index']

    state = _state_shard(args) * _one_projector(args, index)
    norm = np.linalg.norm(state)
    return norm * norm