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Applications of Quantum Computers
With the ability to perform entire systems of analysis at once, it becomes possible to arrive at the conclusions somewhat from the “wrong side”. It is classically rather easy to multiply two numbers, 345 x 611, and arrive at a result, 210795. Of much more time consumption is the reverse operation. Given any value, find two appropriate factors. While not impossible, the problem become progressive more complicated with the size of the value involved. In the cases of things such as cryptography, it is very common for systems of relatively prime values to be hundreds of digits long.
With the case of cryptography, one requirement is the factoring of extremely large values. In classical computing this is an operation that increases in time exponentially with the size of the value in question. By creating a pair of quantum registers, each of which essentially hold all possible binary values that can be represented with their number of bits, it becomes possible to cyclically resolve in time that only increases relative to the square of the size of the value, rather than the exponent.
Once a pair of qubits have been entangled, they can influence one another instantly over any distance. While it is not possible in a single lone bit to tell at the other end what influences have been made upon the paired qubit, it is possible as long as you have a second constant qubit that is also entangled with a relative pair. This may sound like it requires two bits of information to arrive at a single bit of transferred information, but in fact there are three different directional motions that can be imparted onto such an object. Along with an “operation” of doing nothing, that is four different possibilities, exactly what would be expected of two bits of classical information.