How is a collapsed qubit similar to a bit?

A quantum bit (qubit) is still a quantum bit after measuring it. It's not transformed into a classical bit by a measurement. So if you measure a qubit then it will become a |0⟩ or |1⟩. Of course at the end of a quantum calculation the |0⟩ and |1⟩ states are normally associated with classical '0's and '1's for the purpose of reporting the result of the calculation, but that shouldn't be confused with the fact that the qubits themselves end up in the quantum |0⟩ and |1⟩ states. Thanks for contributing an answer to Physics Stack Exchange! • Please be sure to answer the question. Provide details and share your research! But avoid … • Asking for help, clarification, or responding to other answers. • Making statements based on opinion; back them up with references or personal experience. Use MathJax to format equations. To learn more, see our

I am Computer Science student and learning about quantum computing. But, I have a problem in understanding Bit and Qubit relationship. A bit with 2 bits = 4 states 00,01,10,11--- 1 state at a time. How is Please, ignore my 'novice'ness in this topic but this is hell interesting. I came across " So, I have gathered something, please rectify me if I am wrong. The only difference is in their states. So, 2 bits will be 00,01,10,11. For 2 Qubits it will also be same i.e 00,01,10,11. Will the diagram look like this: Now, the probability that which state will it enter depends on the superposition of 0 and 1. Where am I wrong? After several discussions on that topic, I came to think that it is more appropriate to separate those different types of "bits" into four instead of two classes: • A deterministic classical bit is an ordinary bit can be either in state $\left|0\right>$ or in state $\left|1\right>$. No other states allowed. • A random classical bit can be in a "unknown" state with probabilities $p_i$: $$p_0\left|0\right>+p_1\left|1\right>,\quad \text$ space • For a pure qubit the space is a manifold defined by the implicit equation $\left|\alpha\right|^2+\left|\beta\right|^2=1$. This manifold is 2-dimensional and is well-known as a • Finally, the space of a mixed qbit states is represented by a 3-dimensional set. That actually corresponds to an interior of a Bloch sphere (a "Bloch ball" if you want). I'll leave out the math, partly because I'm not sure I remember it precisel...

In October 2019, researchers at Google announced to great fanfare that their embryonic quantum computer had solved a problem that would overwhelm the best supercomputers. Some said the milestone, known as quantum supremacy, marked Whether it's calculating your taxes or making Mario jump a canyon, your computer works its magic by manipulating long strings of bits that can be set to 0 or 1. In contrast, a quantum computer employs quantum bits, or qubits, that can be both 0 and 1 at the same time, the equivalent of you sitting at both ends of your couch at once. Embodied in ions, photons, or tiny superconducting circuits, such two-way states give a quantum computer its power. But they're also fragile, and the slightest interaction with their surroundings can distort them. So scientists must learn to correct such errors, and Kuperberg had expected Google to take a key step toward that goal. "I consider it a more relevant benchmark," he says. If some experts question the significance of Google's quantum supremacy experiment, all stress the importance of quantum error correction. "It is really the difference between a $100 million, 10,000-qubit quantum computer being a random noise generator or the most powerful computer in the world," says Chad Rigetti, a physicist and co-founder of Rigetti Computing. And all agree with Kuperberg on the first step: spreading the information ordinarily encoded in a single jittery qubit among many of them in a way that maintains the information e...

Ok, I have done a lot of research on Quantum computers. I understand that they are possibly the future of computers and may be commonplace in approximately 30-50 years time. I know that a Binary is either 0 or 1, but a Qubit can be 0 or 1. But what I don't understand is how it can be anything other then 0 or 1. Surely a computer can only understand on and off, despite however fast it may be? Probably the easiest analogy is to probabilities. If your computer can flip fair coins, you can think of each coin being in state Tails with probability 1/2 and in state Heads with probability half. So it's appropriate to think of a coin not as a bit but as a vector of two elements $(p_T, p_H)$, where $p_T$ is the probability of tails, $p_H$ is the probability of heads and we have that $p_T \geq 0$, $p_H \geq 0$, and $p_T + p_H = 1$. Once we sample a coin its state "collapses" to either tails or heads. Just about the same happens with qubits. You can also think of quibit as being "in between" two states. It's also easiest to think of qubit not as a bit but as a vector of two elements $(q_0, q_1)$. Now, however, we allo $q_0$ and $q_1$ to be negative, and even further, to be any two complex numbers, as long as $|q_0|^2 + |q_1|^2 = 1$. Just as with sampling coins, once you measure a qubit, it collapses to either $0$ or $1$, and in fact you get $0$ with probability $|q_0|^2$ and $1$ with probability $|q_1|^2$. However, and this is the crucial part, these quantum probabilities can be made ...

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reader comments 90 with Quantum information is the physics of knowledge. To be more specific, the field of quantum information studies the implications that quantum mechanics has on the fundamental nature of information. By studying this relationship between quantum theory and information, it is possible to design a new type of computer— a quantum computer. A largescale, working quantum computer—the kind of quantum computer some scientists think we might see in 50 years—would be capable of performing some tasks impossibly quickly. To date, the two most promising uses for such a device are Although quantum search is impressive, quantum factoring algorithms pose a legitimate, considerable threat to security. This is because the most common form of Internet security, Quantum computers are fundamentally different from classical computers because the physics of quantum information is also the physics of possibility. Classical computer memories are constrained to exist at any given time as a simple list of zeros and ones. In contrast, in a single quantum memory many such combinations—even all possible lists of zeros and ones—can all exist simultaneously. During a quantum algorithm, this symphony of possibilities split and merge, eventually coalescing around a single solution. The complexity of these large quantum states made of multiple possibilities make a complete description of quantum search or factoring a daunting task. Rather than focusing on these large systems, therefore...