Questions tagged [classical-computing]
For questions about the relation between quantum computing and classical computing, such as their relative performance.
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CPTP, Kraus representation and classical registers
What is the best mathematical representation of a quantum system that has some classical registers and some quantum registers?
I'm asking because I'm considering any "physical" process $\pi()$ that ...
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3answers
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What does the $\sqrt{NOT}$ gate have to do with irreversibility?
In his essay "Why now is the right time to study quantum computing" Aram Harrow writes, after describing the action of the $\sqrt{NOT}$ gate, that:
However, if we apply $\sqrt{NOT}$ a second time ...
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1answer
38 views
Will quantum computers pass the Turing test? [closed]
Will quantum computers be able to pass the Turing test sooner than classical computers?
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1answer
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Is there anything that can be programmed on a classical computer but not on a quantum computer?
Would we need to create new algorithms that only work on quantum computers or would be simply edit codes in languages such as C++ to involve the new primitives from quantum computing? Are there ...
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2answers
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Does quantum computing already possess the level of abstraction to be explicable even without knowledge of physics?
Currently, quantum computer science (in contrast to classical computer science) can mostly only be understood if one has a good inside knowledge of physics, or more precisely quantum physics. Only ...
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2answers
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Does the massive parallelization in Quantum computing imply parallelization of input (as opposed to Turing machine)?
Being a newbie in this field, I'm trying to understand what types of real-life workloads are suitable for migrating to Quantum computers.
Intuitively, it seems to me that if a Quantum computer ingests ...
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2answers
56 views
Are quantum gates analogous to ASSPs in classical computing?
After reading some with regard to the quantum computing gates and the comparison to classic gates it seems that the quantum computer, at least for the time being, is not viewed as a programmable ...
2
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1answer
111 views
What concepts from classical computing are vital for quantum programmers?
Many scientific programmers get by fine without having a computer science background, i.e. they don't need to know the machinery behind the prevailing paradigm of 0's and 1's (bits), let alone basic ...
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Quantum circuits explain algorithms, why didn't classical circuits?
When explaining a quantum algorithm, many revert to 'circuit-speak' by drawing a diagram of how qubits split off into transformations and measurements, however, rarely if not never would someone ...
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2answers
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Are binary states (bits) pervasive in classical physics?
If
quantum physics is a refinement of classical physics, and
quantum computing is a refinement of classical computing, and
classical computers use bits (binary digits) whereas quantum computers use ...
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0answers
41 views
Can Quantum Voting Machine replace Electronic Voting Machine (EVM) in future?
Some countries like India are using standalone electronic voting machines (EVM) for elections. They are not interconnected, use no power cables (run on battery), no wireless cards and are secure ...
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If classical physics emerges in some limit of quantum mechanics, shouldn't there be intermediate classical-quantum computers?
Presumably quantum mechanics really is the way the universe works, and it appears we don't really understand where the boundary between quantum mechanical phenomena like interference end and classical ...
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1answer
588 views
Quantum computer vs. supercomputer performance [closed]
Does anybody have any other comparisons between a universal quantum computer and a classical computer that might shed some light into how their performance compares?
Below is what I've been able to ...
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4answers
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Does a quantum computer have a clock signal and if yes how big is it?
I think there can't be a computer running software without having a clock signal.
A fast classical computer has a clock rate between 4 to 5 GHz.
If quantum computers are so much faster they must ...
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1answer
67 views
Can quantum computer perform classical computation? [duplicate]
I was going through a paper in which protocol said that the party computes modulo 'd' sum of other party secrets directly. It was not mentioned that the computation is classical. Can I assume that it ...
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1answer
53 views
How can classical computations be non-unitary?
Given that classical physics emerges from quantum physics on a macroscopic scale, and all quantum operators are unitary, how are we able to perform non-unitary operations (such as setting a register ...
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0answers
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Error message for Classical Probability coding in Python
strong textHi guys I am doing a coding exercise for probabilities in vectors.
Exercise 2 (1 point). As you recall, we may also write the probability distribution as a stochastic vector pā =[p0p1]pā=...
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2answers
185 views
Are there many practical problems for which Grover's algorithm beats the best heuristic classical algorithm?
It's well known that, given an oracle for a function $f$ from a very large set $S$ (of order $N \gg 1$) to $\{0, 1\}$, Grover's algorithm can find an element of $S$ that maps to 1 with $\sim \sqrt{N}$ ...
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2answers
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A quantum computer that doesn't use entangled qubits has the same computational power as a classical one?
Is the statement in the question correct?
I would love to receive an explanation as to why it is or isn't.
I have a computer science degree background and I am a beginner learning the fundamental of ...
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1answer
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Classical and quantum limits to classical copying?
The no-cloning theorem can be sharpened to give quantitative bounds on the fidelity with which an arbitrary quantum state can be copied. Is there a similar picture available for classical copying? ...
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1answer
576 views
Can a quantum computer run classical algorithms?
I realize that fundamentally speaking quantum and classical computers might as well be apples and oranges, and that for very specific problems such as integer factorization with Shor's algorithm ...
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0answers
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Comparing CPU to QPU In terms of processing power
The current processors are limited by the speed of the electrons but quantum processors take advantage of the properties of subatomic particles. But the question is how to compare the processing power ...
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1answer
379 views
What exactly makes quantum computers faster than classical computers?
What feature of a quantum algorithm makes it better than its classical counterpart? Are quantum computers faster than classical ones in all respects?
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References on quantum arithmetic circuit complexity
In classical computing, arithmetic circuit complexity is apparently a big topic. But I couldn't find much about the complexity of quantum arithmetic circuits. Almost all references like arXiv:1805....
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1answer
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Implementing piecewise functions on a quantum computer
I am curious about how to do implement functions like $$f(x)=\begin{cases}
2x &\text{if} &0\leq x <0.5 \\
x/2 &\text{if} &0.5\leq x<1
\end{cases}$$
Do we implement this like ...
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1answer
124 views
Large size of matrices for little outcome [closed]
I am stuck in a dilemma about how to proceed with a quantum computing algorithm that changes the original state of a system to another.
Say I have a superposition of all $8$ bit integer values that ...
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1answer
70 views
Is it possible to construct an equivalent quantum circuit from a CORDIC-based digital circuit?
DaftWullie mentions an interesting point here:
let's assume that we know an efficient classical computation of $f(x)$. That means we can build a reversible quantum computation that runs in the same ...
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What is the difference in computational power between qubit and bit (transistor)? [duplicate]
If I use for example 5-qubit IBM-Q quantum computer and we accept the law of quantum parallelism ($n$ qubit = $2^n$ ordinary bits), so does it mean that computational power of this computer is equal ...
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4answers
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Implementing “Classical AND Gate” and “Classical OR Gate” with a quantum circuit
Quantum cNOT Gate (Classical XOR Gate)
A "Controlled NOT (cNOT) Gate" flips the 2nd qubit if the 1st qubit is $\left|1\right>$, and returns the 2nd qubit as-is if the 1st qubit is $\left|0\right&...
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1answer
85 views
Aren't reversible logic gates a necessity for efficiently executing quantum algorithms?
The Wikipedia article on logical reversibility says:
...reversible logic gates offered practical improvements of
bit-manipulation transforms in cryptography and computer graphics.
But I guess ...
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1answer
403 views
Reversibility and irreversibility of logic gates (quantum vs classical)
I have been told that one of the great keys that unlock quantum computing's potential is the reversibility of quantum logic gates as for classical gates there's some loss of information, but I cannot ...
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2answers
236 views
Does quantum computing relate to stochastic computing in any way?
I'm a bit familiar with the concept of stochastic computing, where numbers are stored in large bit streams called "Stochastic Numbers", which represent numbers in the domain $[0,1]$ typically.
The ...
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1answer
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FANOUT with Toffoli Gate
Figure 1.16: FANOUT with the Toffoli gate, with the second bit being the input to the FANOUT (and the other two bits standard ancilla states), and the output from the FANOUT appearing on the second ...
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Quantum Supremacy: How do we know that a better classical algorithm doesn't exist?
According to the Wikipedia (Which quotes this paper https://arxiv.org/abs/1203.5813 by Preskill) the definition of Quantum Supremacy is
Quantum supremacy or quantum advantage is the potential ...
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2answers
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Understanding (theoretical) computing power of quantum computers
I am very new to quantum computing and just try to understand things from a computer scientist's perspective.
In terms of computational power, what I have understood,
100 ideal qubits ... can ...
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1answer
73 views
Could we use varying voltage with programmable gates?
One of the benefits I'm reading about qubits is that they can be in an infinite number of states. I'm aware of Holevo's bound (even though I don't fully understand it). However, it made me think of ...
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2answers
343 views
Can we speed up the Grover's Algorithm by running parallel processes?
In classical computing, we can run the key search (for example AES) by running parallel computing nodes as many as possible.
It is clear that we can run many Grover's algorithms, too.
My question is;...
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1answer
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Can a stored programming model be applied to a Quantum Computer?
A stored programming computer model is that where a central memory is used to store both instructions and data that they operate on. Basically all the classical computers of today that follow the von ...
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3answers
257 views
What is quantum computing vs. what is not quantum computing
That is to say,
what are some common or popular misconceptions about what constitutes quantum computing?
and
how are those things misconceptions?
It could help in explaining to frame this ...
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3answers
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Simplest algorithm for intuitively demonstrating quantum speed-up?
What's the simplest algorithm (like Deutsch's algorithm and Grover's Algorithm) for intuitively demonstrating quantum speed-up? And can this algorithm be explained intuitively?
Ideally this would be ...
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4answers
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Are classical bits quantum?
A bit is a binary digit, typically 0 or 1.
Until a value is assigned (or a measurement is made) a bit is in a superposition of the entangled binary pair, is it not?
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2answers
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The process for transferring qubits between locations
I understand that right now qubits are physical entities in a Quantum Computer and I am playing around on the IBM Quantum Computer as well as the Q# language and dipping my toes into the Quantum world ...
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4answers
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Are quantum computers just a variant on Analog computers of the 50's & 60's that many have never seen nor used?
In the recent Question "Is Quantum Computing just Pie in the Sky" there are many responses regarding the improvements in quantum capabilities, however all are focussed on the current 'digital' ...
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6answers
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If quantum speed-up is due to the wave-like nature of quantum mechanics, why not just use regular waves?
The intuition I have for why quantum computing can perform better than classical computing is that the wavelike nature of wavefunctions allow you to interfere multiple states of information with a ...
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1answer
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What classical public key cryptography protocols exist for which hacking is QMA complete or QMA hard?
Such a public key cryptosystem would be "quantum safe" in the sense that quantum computers cannot efficiently solve QMA hard problems.
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13answers
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Is quantum computing just pie in the sky?
I have a computer science degree. I work in IT, and have done so for many years. In that period "classical" computers have advanced by leaps and bounds. I now have a terabyte disk drive in my bedroom ...
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2answers
241 views
Are we certain that quantum computers more efficient than classical computers can be built?
I mean are we certain that they will be able to provide us a huge improvements (in some tasks) compared to clasical computers?
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3answers
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Will Moore's Law be no longer effective once quantum computers are created? [duplicate]
Moore's law states that computer power doubles in every 18 months (more formally: "the number of transistors in a dense integrated circuit doubles about every two years."). Statistics suggest that ...
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Is quantum cryptography safer than classical cryptography?
Quantum computing allows us to encrypt information in a different way compared to what we use today, but quantum computers are much more powerful than today's computers. So if we manage to build ...
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7answers
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Why is it harder to build quantum computers than classical computers?
Is it because we don't know exactly how to create quantum computers (and how they must work), or do we know how to create it in theory, but don't have the tools to actually execute it in practice? Is ...
