In our history human technology consisted of our brains, fire and sharp sticks.
When fire and sharp sticks became power plants and nuclear weapons the biggest upgrade has happen to our brains.
Since 1960's the power of our brain machines has kept, growing more rapidly. allowing computers to get smaller and more powerful at same time, but this process is about to meet its physical limits. computer parts are approching the size of an atom, to understand why this problem become, we have to clear up some basics.
Computer is made of very simple components. doing very simple things. computer is representing data, that means of processing it and control mechanisms. computer chips contain modules which contain logic gates which contain transistors. transistor is the simplest from of a data processor in computers, basically a switch that can either block or open the way for information coming through. this made up with bits and which can be set to either 0 or 1.combinations of several bits are used to represent more complex information. transistors are combined to create logic gate which still do very simple stuff. for example ,an AND circuit sends an output of 1 if all of its inputs are 1 and output of 0 otherwise.
Combinations of logic gates finally form meaningful modules, say ,for adding two numbers. once you can add ,you can also multiply a nd once you can multiply, you can do anything. since all basic operations are literally simpler than first grade math, you can imagine a computer as group of 7-year-olds answering really basic math questions. large enough bunch of them could compute anything from astrophysics to Zelda.
Yet, with parts getting tinier and tinier, physics are making things tricky.in a nutshell a transistor is simply an electrical switch.in electricity is electrons moving from one place to a different . so, switch is a passage that can block electrons from moving in one direction. today, a typical scale for transistors is 14 nanometers, which is about 8 times but the HIV virus diameter, and 500 times smaller than a red blood corpuscle . as transistors are becoming smaller to the size of only a few atoms, electrons may just transfer themselves to the other side of a blocked passage. via processing called quantum tunneling.
In the quantum realm ,physics works quite differently from the predictable ways we are won't to , and traditional computers just stop making sense. we are approaching a true physical barrier for our technological progress . to solve this problem, scientists are trying to use these unusual quantum properties to their advantage, by building compute computers.
Quantum computing is concentrated on developing technology base on the principles of scientific theory .which explains the behavior of energy and material on the atomic and subatomic levels. computers that we use today can only encode information in bits that take the worth of 1 or 0.
In Normal computers ,bits are the smallest unit of information. Quantum computers are qubits which can also be set of one of two values. A qubit can be any two level quantum system, such as a spin and magnetic field. 0 & 1 are this system's possible states, like the photons horizontal or vertical polarization.
In the quantum world ,the qubit doesn't have to be just one of those, it can be any proportions of both states at once. this is called superposition, but as soon as you test its value ,say by sending the photon through a filter, it has to make a decision to be either vertically or horizontally polarized.so as long as it's unobserved, the qubit is in a superposition of probabilities for 0 and 1 ,and you can't predict which it'll be, but the instant you measure it, and it collapses into one of the definite states.
Superposition is game changer. four classical bits can be of two to the power of four different configurations at a time. that's 16 possible combinations, out of which you can use just one. qubit Manipulation is mind bender as well. Normal logic gets a simple set of inputs and produces any definite output. quantum gate manipulates an input of superpositions ,rotates probabilities, and produces another superposition as its output.
So a quantum computer sets up some qubits ,applies quantum gates to entangle them and manipulate probabilities, then finally measure the result ,collapsing superpositions to an actual sequence of 0s and 1s.what this means is that you get the entire lot of calculations that are possible with your setup ,all done of at the same time. Ultimately , you can only measure one of the results and it'll only probably be the one you want, so you any have to double check and try again. but by cleverly exploiting superposition and entanglement, this can be exponentially more efficient than would ever be possible on a normal computer.
One of them database searching to find something in a database ,a normal computer may have a test every single one of its entries. Quantum computers algorithms need only the square root of that time, which for large database, is a huge difference. the most famous use of quantum computers is ruining IT security.
Right Now your browsing ,Email, and banking data is being kept secure by an encryption systemin which you give you everyone a public key to encode messages only you can decode. the problem is that this public key can actually be used to calculate your secret private key, doing the necessary math on any normal computer would literally take years of trial and error, but a quantum computer with exponential speed-up could roll in the hay during a breeze.