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Re: Quantum Computing with Molecules




Factoring large digit numbers with quantum computers does have a major impact on encryption based security systems. With many of the cryptographic systems today such as the RSA depending on the difficulty of finding two prime factors of a number, making this task efficient will definitely weaken their security potential if not obsolete. However, I believe that new problems will always give rise to new solutions.
The power of a quantum computer depends on the number of qubits it is built on. At the moment I believe that the highest number of qubits in an experimental quantum computer ever constructed was around 7. This was done in 2000 at Los Alamos National Laboratory using only a single drop of liquid. With 7 qubits, this computer would be able to perform operations on 2^7 different numbers at the same time instead of just one on today's computers (not including multicore processors). Of course, having around 7 qubits of processing power in a quantum computer won't be much of a threat to cryptography right now. But scientists predict that we would have a computer with 100 qubits within this decade. In addition, once a 1000 qubit computer is constructed, the security of many cryptographic systems will be broken. With 2^1000 different numbers being able to be operated on at a single time, and with the speed of today's computers being measured in MIPS (million of instructions per second), one could only imagine the computational power of such a computer. I am guessing that with this computer, the number of instructions that could be processed would be greater than 10^300 instructions per second. Of course I am being optimistic, but this is a possibility. Having a leap from 10 qubits to 100 in a quantum computer within this decade is not impossible. One problem in constructing such a large nqubit computer is that all the operations using the quantum logic gates must be completed before the information inside the qubits decohere (as stated in the article). The more qubits in a qubit register that we want processed, the greater number of logic gates, and the greater the number of these gates, the longer it takes for the entire logic operation to be completed. There seems to be many research in speeding up the quantum gates by using different materials, and the results they are providing are quite promising. At the rate of advancements in computer science I definitely see the construction of a usable quantum computer happening within this century if not decade.
Now to the threat of cryptography brought up by quantum computers. Some of the methods invented for computer encryptions in the late 20th century was thought to require a few thousand years or so to break. This was of course proved wrong with the joint effort of many privately owned computers and/or organizations over the internet. An example of this is the cracking of the 56bit Data Encryption Standard algorithm in 1999 by two companies working together (done in 23 hours). When an encryption like this is believed to be no longer secure, it seems that the best course of action is usually raising the number of bits in the encryption system thereby making it harder to crack. By the way the encryption most used on the internet today is the 128 SSL encryption method so I guess nobody has been able to crack this efficiently yet. With the introduction of quantum computers, the most obvious method in increasing or maintaining cryptographic efficiency would be to raise the number of bits as well. The increase would definitely have to make the encryption depend on more bits than the capacity of qubits in a quantum computer (maybe 2^1000 bit encryption, I think). Storing this number of bits may not be a problem either since the storage capacity of qubits would also be massive. To sum it up, I believe that we will see quantum computers within the early 21th century and that cryptography may not be at risk as some people believe.
Just a thought :) 





