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This isn't a particularly good introduction to quantum computing. The fact that we can't scale down transistors into the quantum realm doesn't have much to do w
by ganonm 9y ago
This isn't a particularly good introduction to quantum computing. The fact that we can't scale down transistors into the quantum realm doesn't have much to do with the real motivation behind making quantum computers. The real motivation for making a quantum computer is that it allows us to perform algorithms that exploit the quantum behaviour of qubits.
To give a concrete example of this, there is a basic quantum logic gate called a Hadamard gate. This takes a qubit in the state |0> and transforms it into a qubit in the state (|0> + |1>)/sqrt(2). The resultant state is what is known as a superposition state - namely a superposition of both the |0> and |1> states. You can think of the |0> and |1> states as being analogous to the 0 and 1 states of a traditional bit. What this means is that when the qubit is measured (read queried) it will return a value of 0 or 1 with equal probability.
The point I'm making is that this is radically different to traditional computing and isn't simply just the next step along in 'valve transistor -> semiconductor -> ?'
- utkarshs12 9y agoHi! I put this guide together and I'm really glad you brought this point up. When I thought of creating this guide, I wanted to make it really easy for beginners to graduate level by level up to quantum gates, which inspired me to instead break the information down in a series. This Part-1 guide in the series is mean't to educate even complete noobs from how a basic computer works and how we have reached the limits of making them any more powerful. While you are accurate when you say Quantum algorithms can help us exploit the quantum behaviour of qubits, we are particularly interested and motivated to utilize them because we can exponentially increase our computing power. I have another follow-up guide coming that would take the readers a few more levels up very soon.
- justinpombrio 9y ago> we are particularly interested and motivated to utilize [quantum computers] because we can exponentially increase our computing power. On some problems. Quantum computers are --- to the best of our knowledge --- exponentially faster at computing some things (e.g. discrete log and factoring), quadratically faster at others (e.g. NP-complete problems), and no better than classical computers at others. (I assume you know this since you're writing an article on quantum computers, but want to clarify for others.)
- utkarshs12 9y agoWell, I kind of knew that people might associate the increment in computing power with that required in their daily computing needs like watching Youtube videos for example; for the same reason I made sure to explicitly mention in the Introduction, that - "it [Quantum Computers] promises tremendous computing power enough to help us solve some really tough mathematical problems that are holding back our progress in a number of fields."
- Shikadi 9y agoIt might be worth noting that this seems more to do with why different transistor types are being used (fin-fets, nano tubes, etc) since we really haven't reached the physical limit of "traditional" transistors yet. I'd also argue that the motivation behind quantum computers is very much unrelated to limitations on transistor sizes, and more about the algorithms that can potentially be much faster than on traditional logic, such as shor's factoring algorithm
- comicjk 9y ago> when the qubit is measured (read queried) it will return a value of 0 or 1 with equal probability To clarify, qubits don't necessarily have equal probabilities of |0> and |1>. If the probabilities were always equal, we wouldn't be able to use quantum computers for anything besides generating coin flips! The "answer" from a quantum computer is encoded as output probabilities of the qubits, which are found by running the calculations a bunch of times and counting the frequency of each |0> and |1> state.
- ganonm 9y agoI think you've misread my comment as what you're saying is incorrect. When a qubit is in the state (|0> + |1>)/sqrt(2) it does have equal probabilities of being measured as either |0> or |1>. I think what you're trying to say is that (|0> + |1>)/sqrt(2) is not the only superposition state a qubit can be in. A qubit can be in any arbitrary position of the two possible states.
- comicjk 9y agoYour original comment is totally correct, but I thought it might mislead beginners - that's why I said "to clarify." I think there is a common confusion about whether a qubit can have probabilities besides 50:50. The Hadamard gate example explains superposition, but tends to increase this misconception, so I also wanted to emphasize the many other possible states and how an answer is extracted from them.
- gaze 9y agoThis is a bit misleading I think. There are a set of quantum algorithms with deterministic outcomes. The right answer will be measured with probability 1, or something very close...