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1500 questions
9
votes
4 answers
Can we use quantum parallelism to calculate many functions at once?
It is well-known that by utilizing quantum parallelism we can calculate a function $f(x)$ for many different values of $x$ simultaneously. However, some clever manipulations is needed to extract the information of each value, i.e. with Deutsch's…
donnydm
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9
votes
1 answer
How to distinguish between collapsed and uncertain qubits in a quantum circuit?
I have been through the Young's double slit experiment. It's a direct proof or instance of showing that a wave is collapsed via observation or measurement, and shows no interference patterns.
I want to do something similar in a quantum circuit, not…
Sayan Dey
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9
votes
4 answers
How can one imagine entanglement in a non-mathematical way?
I understand the theoretical concept of an entanglement and what it means for our computation to have two entangled qubits, but what does it really mean when two qubits are entangled? How are they entangled in the first place? I mean in the physical…
Blubsiwubsi
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9
votes
2 answers
Why does the surface (quantum error correction) code have such a high threshold for errors?
Is there an intuitive explanation why the surface code fares so much better than older quantum error correction codes in terms of its high error threshold, with thresholds of up to a few percent rather than some ppm? If so, what is it?
I am…
user1039
9
votes
1 answer
Are almost-Clifford circuits almost easy to simulate?
Circuits consisting entirely of Clifford operations in $\{X, Y, Z, H, S, \text{CNOT} \}$ are "easy" to simulate classically since there is a method that can fully compute such circuits over $n$ qubits with $O(n^2)$ complexity.
I'm curious if…
forky40
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9
votes
2 answers
How to recover the normalization constant of the HHL solution
HHL solves the linear equation $Ax=b$ by the quantum state $|x\rangle=A^{-1} |b\rangle$. However, the quantum state $|x\rangle$ is normalized and thus diffs a normalization constant from the solution vector $x$. My question is how to recover the…
user14297
- 91
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9
votes
2 answers
Is there a name for the 3-qubit gate that does NOT NOT NOTHING?
It seems to me that the "disjunction gate" (aside: is that its proper name?) can be thought of as the combination of three gates, G1, G2, and G3, where G2 is the CCNOT gate, and $G1 = G3 = ¬_a \otimes ¬_b \otimes I_c$. For context, see the bottom…
Ben Hocking
- 193
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9
votes
4 answers
Superposition of quantum gates
In the standard model of quantum computation a gate is a unitary that acts on a subsystem. Physically, it can be implemented by some device. Now, any device is also a part of our quantum world, thus it has a quantum state. This quantum state, in…
Danylo Y
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9
votes
1 answer
What do double wires mean in quantum circuits, and how do they relate to if statements?
The circuit
can be translated to the following code:
operation Teleport(msg, there) {
let register = AllocateRegister();
let here = register;
H(here);
CNOT(here, there);
CNOT(msg, here);
H(msg);
// Measure out the…
R. Chopin
- 1,219
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9
votes
1 answer
Inequality constraints on D-Wave (using PyQUBO)
Inequalities cannot be directly converted into a QUBO form. By inequality, I mean something like this:
0⩽ Expression ⩽ N.
We can introduce a slack variable and convert it to an equality problem:
⟹ Expression + s = N
where:
s ∈ Z,
s ∈ [0,N]
Since the…
amp
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9
votes
2 answers
What does it mean to "measure an operator"?
I was reading a book and then I found this statement. I will put the text as well as a screenshot of the text.
The expectation value of an operator is the mean or average value of that operator
with respect to a given quantum state. In other words,…
user27286
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9
votes
2 answers
Is there a good reason to use T-count minimization for circuits executed on current IBM open quantum systems (real hardware)?
As far as I understood from a series of papers, minimizing the T-count in Clifford+T circuits is essential for fault-tolerant quantum computing:
While techniques such as magic state distillation and injection allow for fault-tolerant…
Psanfi
- 306
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9
votes
1 answer
Can quantum computing speed up Bayesian learning?
One of the biggest drawbacks of Bayesian learning against deep learning is runtime: applying Bayes' theorem requires knowledge on how the data is distributed, and this usually requires either expensive integrals or some sampling mechanism (with the…
fr_andres
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9
votes
1 answer
Is there any source which tabulates quantum computing algorithms for simulating physical systems?
I was wondering if there is a source (online or review article) which tabulates recent algorithms, and their complexities, used in simulating various physical systems. Something along the lines of:
Physical System 1: Quantum Field Theory…
jman
- 453
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9
votes
3 answers
How are the IBM's and Google's Hadamard gates fabricated and operated?
There are thousands of articles, books and web sites describing the Hadamard Gate from a theoretical point of view.
But I haven't been able to find any photo about any real implementeation of a Hadamard Gate on superconducting circuits nor any…
skan
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