How does a Quantum Computer Work?

[vgane]

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https://www.youtube.com/watch?v=g_IaVepNDT4

A quantum computer works in a totally different way from a classical computer. Quantum bits or 'qubits' can exist in a superposition state of both zero and one simultaneously. This means that a set of two qubits can be in a superposition of four states, which therefore require four numbers to uniquely identify the state. So the amount of information stored in N qubits is two to the power of N classical bits.

 

[tks]

In quantum computing, an exponential amount of information is needed to describe the state of a given computational model as illustrated in the youtube segment. This obviously does not imply that it is exponentially more powerful. The algorithms to exploit this is still being developed by major players.


There are some uniqueness about information stored in a quantum computing platform. It is unique because information stored cannot be copied! The very act of reading can disturb the storage.




This has given rise to a very novel basis for quantum cryptography. It is based on the principle that the state of a quantum object cannot be read without changing its very nature. So any information transmitted in the form of single photons over fiber channels will, in the case of an attempted hack, self-destruct.


The intended recipient will then receive an unintelligible mess, revealing the failed attack. Theoretically, this makes quantum encryption unhackable.

In another 5 years one will know the viability of such computing platforms. There are also attempts to leverage the 'quantum coupling' and mysterious action at a distance aspects of quantum systems ( I had a post in General section on Nature of Reality citing recent experiments). This coupling is also looked into in novel research for a new computing platform.

 

[mskmoorthy]

There is a blog by a quantum computing expert (Prof. Scott Aronson http://www.scottaaronson.com/(MIT)) discusses the result here http://www.scottaaronson.com/blog/?p=2555
That blog contains a link to a short paper on quantum annealing http://www.scottaaronson.com/troyer.pdf