It is possible. Let's say I have access to all computers and servers in the world and can use at least 10 % of their power to generate all bitcoin wallets and I have a big enough storage drive to get the results. It would take a few years, but I will have all those keypairs. Invent a better algorithm for generation, speed it up and maybe it will take even less time. Index the database and there you have it. The other reason as to why you will never know about it, is because nobody who would do such a thing would tell anyone about it. Why would they? Drop the bitcoin price? Set a world panic? Destroy bitcoin? Why would you, if you have access to all bitcoins? Why would you even take more than you need? Why not just empty the long lost wallets, and nobody would even notice. There are far better purposes for quantum computers than to generate bitcoin keypairs, let's do some calculations to get us further into space, move to Mars, improve statistics, make science breakthroughs, etc.
Translation: Ill-informed idiot who whines that merit should be awarded by bots (!) is fishing for merit by posting innumerate nonsense in Development & Technical Discussion.
If you don’t know, then say you don’t know. I admit, the set of things I do not know is infinite. But don’t make stuff up and post it in an authoritative-sounding manner. Nobody is buying what you’re selling.
I even dont know what these quantum computers are because I am a newbie here in this ecosystem. Help me out of this threat 
Try reading the thread. Many intelligent answers were given back in December.
This is officially the spam megathread of Development & Technology Discussion.
Let's say I have access to all computers and servers in the world and can use at least 10 % of their power to generate all bitcoin wallets and I have a big enough storage drive to get the results. It would take a few years,
You might want to double check your maths...
There are 2160 different addresses.
2160 = 1461501637330902918203684832716283019655932542976
[...correct maths...]
The entire universe since the Big Bang has only existed for about 13.8 BILLION years. That means you'd have to continue this process from the beginning of the Big Bang until today, and then repeat that 453,508 more times!
THAT SOUNDS LIKE A LOT MORE THAN "a few years" TO ME! (and with a lot more computing power than you were suggesting).
nice one
we don`t have to worry ... but there is a way if someday... someone.... create some ASIC kind of computer to generate 1PentaBillion addresses/second ??
((“1PentaBillion” = 5 billion addresses. What did you think it meant?
Although your “consumer-grade” laptop won’t be able to, there are already many computers which can generate that many addresses in a second. Easily. But it makes no difference. Compared to 2160, the difference between 1 million and 5 billion is not so impressive.
ASICs are not magical. They are simply Application-Specific Integrated Circuits, highly optimized to run one specific program which is literally cast in silicon. They cannot defy the laws of physics, much less the laws of mathematics. There is still a limit on how fast they can perform computations. Also, importantly: They need energy.
2128 is an infinitesimal fraction of 2160; and a 2128 security level is already what I call “boil the oceans security”, because the energy required for 2128 computations would boil the oceans (and more...). It is humanly impossible to perform such vast amounts of computation, and it will always be humanly impossible.
You just do not get how big these numbers are.
. Back into executing an act, there is three elements. 1. Motive - What possible motive a person will drive him to destroy bitcoin if he posses a quantum computer wherein in fact there are numerous advantages he can get if he use one in the arena of virtual currency, 2. Instrument - the quantum computer itself, 3. Opportunity - there are lots of opportunities in the world of cyberspace. 
