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1500 questions
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3 answers
Does the oracle in Grover's algorithm need to contain information about the entirety of the database?
Grover's algorithm is often described as a way to search a database in $O(\sqrt{N})$ time. For using it we need an oracle gate that represents some function $f$ such that $f^{-1}(1)$ is the answer. But how do you actually make such a “database…
Norrius
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3 answers
Quantum tensor product closer to Kronecker product?
Coming more from a computer science background, I never really studied tensor products, covariant/contravariant tensors etc. So until now, I was seeing the "tensor product" operation mostly as (what appears to be) a Kronecker product between the…
Léo Colisson
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1 answer
Are there any encryption suites which can be cracked by classical computers but not quantum computers?
Are there any encryption suites that can be cracked by usual computers or super computers, but not quantum computers?
If that's possible, what assumptions will it depend on? (Factorizing big numbers, $a^b\pmod d$ $a^c\pmod d$ $a^{bc}\pmod d$ etc...)
MCCCS
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4 answers
Do real commercial quantum computers exist?
We have been reading about quantum computers being developed and tested in labs.
And also, we have quantum simulator programs that use limited virtual qubits (up to 30-40 qubits if cloud-based).
And we have also started learning new quantum…
Koder101
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2 answers
What is the advantage of quantum machine learning over traditional machine learning?
Why exactly is machine learning on quantum computers different than classical machine learning? Is there a specific difference that allows quantum machine learning to outperform classical machine learning?
Rob James
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2 answers
What are the benefits of using quantum machine learning?
I have been investigating uses for quantum machine learning, and have made a few working examples (variations of variational quantum classifiers using PennyLane). However, my issue now is its relationship with classical machine learning. At the…
Andrew
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10
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2 answers
Procedures and intuition for designing simple quantum circuits?
I'm working my way through one of the quantum circuits sections in Nielsen and Chuang and I'm struggling to get a feel for the basics of circuit construction. For example, one of the exercises is as follows:
This exercise seems really simple on the…
Arthur Allshire
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2 answers
How does evolving a two-qubit state through a CNOT gate entangle them?
Reading into CNOT gate I understand that, mathematically, such a gate entangles the control qubit and the target. (the resulting state is $\frac{1}{\sqrt 2}(|00\rangle+|11\rangle)$)
However, looking at the "truth table" of the gate, it seems as…
ItamarG3
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1 answer
Preparing a quantum state from a classical probability distribution
Suppose I have a black-box unitary $U_p$ which is described as follows: given a finite probability distribution $p:\{1,\ldots,n\}\rightarrow \mathbb{R}_{\geq0}$, where $\sum_{x=1}^n p(x)=1$, the action of the black box on a basis is given by…
Condo
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3 answers
Simplification of "rotation swapping" circuit
While trying to simplify a certain 2-qubit quantum circuit, I managed to get it down to this:
But by inspecting the corresponding two-qubit unitary directly, I can come up with the arguably simpler:
where the rotation operator "moved" to the first…
Andrea Olivo
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10
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1 answer
New Hybrid-HHL algorithm vs VQLS
A team of researchers has realized hybrid quantum algorithm for solving a linear system of equations with exponential speedup that utilizes quantum phase estimation, the algorithm demonstrates quantum supremacy and holds high promise to meet…
Carlos Alfredo Vergara Rojas
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10
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1 answer
Why Google has used $\sqrt{X}$ and $\sqrt{Y}$ instead of $X$ and $Y$ in supremacy experiment?
In supremacy experiment Google has used $\sqrt{X}$ and $\sqrt{Y}$ as two of their single qubit gates (paper).
So My questions are:
Is there any specific reason for choosing these gates and not $X$ and $Y$ instead?
Is it because of technical…
Ali s.k
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3 answers
Is there quantum advantage to be had with a D-Wave computer in 2020?
I've seen a lot of excitement in the popular press about the computers made by D-Wave Systems, but when I dig deep the only practical things that I can figure out that one can do with the computer are variations of:
Train one's staff in the use of…
vy32
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1 answer
Quantum algorithm for QR and SVD matrix decomposition?
I would like to know if exist a quantum algorithm tailored to compute the QR decomposition and SVD of a matrix? Pointers to relevant papers will be very appreciated.
user3116936
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2 answers
Why is Deutsch's gate universal?
(This is related to Exercise 4.44 in Nielsen and Chuang)
Deutsch quantum gate is basically a $iR_x(\alpha \pi)$ gate with two control qubits. The constant $\alpha$ is an irrational number that allows to perform any rotation $R_x (\theta)$ by sending…
MBolin
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