No! Well not really light and really strong.
If you want the strongest, most unbreakable bike lock it is going to be very heavy. On the other hand, if you want a very light lock then scumbag thieves will be able to cut through it with not much more than a pair of scissors.
In between these two extremes is a continuum of locks available at widely varying levels of security, weight and price. However, for quality lock brands like Kryptonite and Abus – (never buy a cheap, poor quality lock) – strength is almost perfectly correlated with weight: The stronger the lock, the heavier it will be!
“Money no object, what’s a very strong but very light lock?”. I’ve had this question asked in the on more than one occasion, but sadly this combination doesn’t exist.