def scissors_shift(potential,delta):
    """Scissors shifts a full potential by delta
    Args:
        potential: a 2D array
        delta: a real number
    Returns:
        shifted_potential: a 2D array
    """
    shifted_potential = potential
    for i in range(len(potential)):
        shifted_potential[i,0] = potential[i,0]
        shifted_potential[i,1] = potential[i,1] - delta

    return shifted_potential