Quantum Computers have been a dream for a few physicists and mathematicians and an intriguing name for most of us.
The story in itself is not too difficult to understand, if we accept something that looks like the truth: in normal computers you are using elements that can be associated with two values, one and zero. If you want to perform logic operations you can manipulate these values to get a result. It turns out that you can also use logic operations to do arithmetics and many more things, like compressing a signal or describing an image.
If rather than using a circuit that can flip-flop between one and zero, depending on the input signal and the structure of the circuit, you happen to have an element that can assume an unlimited number of values it is obvious that you have got something much more powerful. Actually the situation is not as clean as it looks. In a computer element, the “bit” is either at the 0 or 1 value. In a quantum computer, so goes the theory, the “q-bit” is at the same time both at 0 and 1 value. It gets more complicated, sorry. In a normal computer when you have 3 bits you can use them to represent any 8 numbers (000 to 111). In a quantum computer the 3 q-bits are “entangled”, that is they constitute a single unity: anything happening at one q-bit instantaneously happens to the others. So if you have 3 q-bits there are 8 values that are concurrently present. By interacting with it (using a laser) you collapse the range of values to a specific one but, and here is the amazing thing, you are actually performing the operation on all the possible values, at the same time.
Whilst the theory is now well progressed and, in theory, we know how to manipulate q-bits, in practice we do not know how to do it and get a sensible result.
Theoreticians, however, have worked hard and have demonstrated several interesting theorems, like the one that with a quantum computer it would be possible to solve factorialization in a blink of an eye.
Factorialization (finding the factors of a number) is a very lenghty process with current computers and this is exploited in cryptography. The keys are made up of two very large prime numbers and the resulting number (the multiplication of the two primes) is used to encript the information. Unless you know the factors there is no way to decrypt the information and finding the factors would take a computer many many years.
If a quantum computer were available the factorialization will be easy and with that will go our cryptographic method.
So far scientists have been able to develop structures containing up to 28 q-bits and this is no small feat (7 q-bits would be enough to work on the factorialization problem). However, no one has been able to create a computer using the q-bit. No one till now.
Researchers at NIST, in Boulder Colorado, have published a paper , Nature Physics, DOI: 10.1038/nphys1453 , reporting their success in building a quantum computer based on 2 q-bits. However, the result obtained in performing 160 different programs on the q-bits has got just over 70% of accuracy. This is not sufficient since once you have to use several q-bits in a row (as you would for factorialising a number) the end result will be a complete nonsense.
Hence, the progress made has made possible to see the horizon (somthing that was not possible before) of the solution but we do not know how long it will take to get there. Someone is actually talking in terms of a rainbow, rather than an horizon: as you get closer it moves away from you. Bankers and military forces can still trust their encrypted data for a while.
If you want to get a bit more of information on this result but you do not feel like getting the full story on the (highly) technical paper take at look at: