How to make the game stop upon death?

I am making a game and I urgently need to know how to make my game stop(including counter) when I die.

This is my enemy script.

using UnityEngine;
using System.Collections;

public class Cubes : MonoBehaviour {
	public float delay = 0.1f;
	public GameObject cube;
	
	// Use this for initialization
	void Start () {
		InvokeRepeating("Spawn",delay,delay);
	}
	
	// Update is called once per frame
	void Spawn () {
		Instantiate(cube,new Vector3(Random.Range(-6,6),10,0),Quaternion.identity);
	}

	public bool readyToKill = false;

}

All help will be greatly appreciated! Thanks in advance!

if(playerIsDead){
Application.Quit();
}

If you mean by stopping the game like when you open a pause menu, then
Time.timescale = 0 might be the solution for you. From there you can fade in a game over window on the canvas to let the user play again or whatever options are available.

I have the player as the game object and I have the script for the enemy that makes the enemy spawn. As the script of the cubes are not a game object and just a script, how do I make it that when the player hits the script (in a way) the player dies or spawns back? Thanks for any help!