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1500 questions
179
votes
13 answers
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 drawer amongst my socks, my phone has phenomenal…
John Duffield
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86
votes
6 answers
What programming languages are available for quantum computers?
From this question, I gathered that the main quantum computing programming languages are Q# and QISKit.
What other programming languages are available for programming quantum computers? Are there certain benefits to choosing particular ones?
EDIT: I…
Pro Q
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78
votes
7 answers
Are there emulators for quantum computers?
Is there any way to emulate a quantum computer in my normal computer, so that I will be able to test and try quantum programming languages (such as Q#)? I mean something that I can really test my hypothesis and gets the most accurate…
Michel Gokan Khan
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78
votes
4 answers
Can a Turing machine simulate a quantum computer?
I know that a Turing machine1 can theoretically simulate "anything", but I don't know whether it could simulate something as fundamentally different as a quantum-based computer. Are there any attempts to do this, or has anybody proved it…
user7
63
votes
7 answers
What are the models of quantum computation?
It seems that quantum computing is often taken to mean the quantum circuit method of computation, where a register of qubits is acted on by a circuit of quantum gates and measured at the output (and possibly at some intermediate steps). Quantum…
Kiro
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53
votes
2 answers
What is meant by "Noisy Intermediate-Scale Quantum" (NISQ) technology?
Preskill introduced recently this term, see for example Quantum Computing in the NISQ era and beyond (arXiv). I think the term (and the concept behind it) is of sufficient importance that it deserves to be explained here in a pedagogical manner.…
agaitaarino
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52
votes
4 answers
How do I show that a two-qubit state is an entangled state?
The Bell state $|\Phi^{+}\rangle = \frac{1}{\sqrt{2}}(|00\rangle + |11\rangle )$ is an entangled state. But why is that the case? How do I mathematically prove that?
user72
50
votes
2 answers
Is there proof that the D-wave (one) is a quantum computer and is effective?
I'm admittedly a novice in this field, but I have read that, while the D-wave (one) is an interesting device, there is some skepticism regarding it being 1) useful and 2) actually a 'quantum computer'.
For example, Scott Aaronson has expressed…
Discrete lizard
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50
votes
6 answers
Programming quantum computers for non-physics majors
I come from a non-physics background and I am very much interested in pursuing Quantum Computing - especially how to program them. Any guidance on how to get started will be very helpful.
Koder101
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49
votes
4 answers
How do I add 1+1 using a quantum computer?
This can be seen as the software complement to How does a quantum computer do basic math at the hardware level?
The question was asked by a member of the audience at the 4th network of the Spanish Network on Quantum Information and Quantum…
agaitaarino
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47
votes
4 answers
Is it possible for an encryption method to exist which is impossible to crack, even using quantum computers?
Quantum computers are known to be able to crack in polynomial time a broad range of cryptographic algorithms which were previously thought to be solvable only by resources increasing exponentially with the bit size of the key. An example for that is…
peterh
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46
votes
5 answers
How does bra-ket notation work?
Quantum algorithms frequently use bra-ket notation in their description. What do all of these brackets and vertical lines mean? For example: $|ψ⟩=α|0⟩+β|1⟩$
While this is arguably a question about mathematics, this type of notation appears to be…
Ella Rose
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45
votes
2 answers
How is the oracle in Grover's search algorithm implemented?
Grover's search algorithm provides a provable quadratic speed-up for unsorted database search.
The algorithm is usually expressed by the following quantum circuit:
In most representations, a crucial part of the protocol is the "oracle gate"…
glS
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44
votes
3 answers
How does a quantum computer do basic math at the hardware level?
On reading this Reddit thread I realized that even after a couple months of learning about quantum computing I've absolutely no clue about how a quantum computer actually works.
To make the question more precise, let's say we have a superconducting…
Sanchayan Dutta
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43
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1 answer
Quantum machine learning after Ewin Tang
Recently, a series of research papers have been released (this, this and this, also this) that provide classical algorithms with the same runtime as quantum machine learning algorithms for the same purpose. From my understanding, the key to all the…
Alex
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