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General >> Tech Talk >> Quantum computers: Glorified term for analog/multilevel logic?
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Message started by vivkr on Feb 8^th, 2010, 2:39am

Title: Quantum computers: Glorified term for analog/multilevel logic?
Post by vivkr on Feb 8^th, 2010, 2:39am

I happened to come across a lot of articles about quantum computing lately, and was intrigued to read something like this:

"While a classical bit can assume only one of 2 states namely 0 or 1, a quantum bit can assume many more values due to entanglement between the 0 and 1 state".

In simplified terms, a quantum bit Q = a*|1> + b*|0> where a and b are scaling coefficients. What then would be the difference between a quantum bit and multilevel logic, or more generally an analog quantity? Is quantum computing merely a glorified expression for analog computers? We do know that analog or multilevel logic could allow faster computing than binary logic because more information can be processed per step.

Of course,t hat would imply that quantum computers have a smaller noise margin than binary computers. So what's the big deal here? Have they found ways to keep the noise margin high?

Vivek

Title: Re: Quantum computers: Glorified term for analog/multilevel logic?
Post by Berti on Feb 8^th, 2010, 3:29am

Hey Vivek,

There was recently a article in IEEE spectrum special issue "winners and losers" about the quantum computer built by D-Wave systems (the project is considered as a loser ;).

http://spectrum.ieee.org/computing/hardware/loser-dwave-does-not-quantum-compute

Title: Re: Quantum computers: Glorified term for analog/multilevel logic?
Post by vivkr on Feb 8^th, 2010, 4:22am

Hi Berti,

I have seen that one, and as a matter of fact, it says something similar about quantum bits

"Whereas a conventional bit can be in one of two states, 0 or 1, a qubit can be 0, 1, or a superposition of 0 and 1."

It speaks about superposition which basically means a linear combination of the 0 and 1 state wavefunctions, or in simple terms, the bit can assume one of many states in between 0 and 1, or in other words, it is like using multi-level logic or analog logic (at some level, even analog quantities are quantized).

So what is the big selling point of quantum computing? Is it simply the ability to handle more information? In that case, analog computers are identically good. Does it for some bizarre reason offer a similar amount of noise margin for multilevel logic operation as it would for 2-level?

Vivek