Most Popular
1500 questions
6
votes
0 answers
Bell State 11 not working for parity curve
I am currently writing a script to automate the creation of parity curves for a 2 qubit bell state and then calculate fidelity and proving entanglement from that (inspired by this paper). It was going really well. I am able to run simulations…
thewolfaxe
- 101
- 2
6
votes
2 answers
Using the HHL algorithm to compute $A |b \rangle$ instead of $A^{-1} |b \rangle$
In the paper "Compiling basic linear algebra subroutines for quantum computers"
here, they discuss (page 2 bottom right) using the HHL algorithm to multiply a vector by a matrix. However, after having read the HHL09 paper, what is being estimated…
IntegrateThis
- 545
- 4
- 14
6
votes
1 answer
Is the quantum Fourier transform efficient if only one control-phase is allowed in the gate set
I have seen Why can the Discrete Fourier Transform be implemented efficiently as a quantum circuit?. This is not a duplicate.
I am familiar with the decomposition of the QFT from Nielsen&Chuang and Preskill's notes, and it requires to be able to…
dragomang87
- 63
- 4
6
votes
1 answer
Equivalent determinant condition for Peres-Horodecki criteria
The Peres-Horodecki criteria for a 2*2 state states that if the smallest eigenvalue of the partial transpose of the state is negative, it is entangled, else it is separable.
According to this paper (page 4, left side), the following is an…
Mahathi Vempati
- 1,621
- 9
- 20
6
votes
1 answer
Why should we use inverse QFT instead of QFT in Shor's algorithm?
Why should we use inverse QFT instead of QFT in Shor's algorithm? When I tried to simulate Shor's algorithm for small numbers, I got an answer even when I used just QFT instead of inverse QFT.
Tech Solver
- 603
- 4
- 9
6
votes
1 answer
Question on state distinguishability
Consider the following protocol.
We are given either
$|\psi\rangle = \frac{1}{\sqrt{2}}(|0\rangle + |1\rangle)$ or $|\phi\rangle = \alpha_{0} |0\rangle + \alpha_{1}|1\rangle$ where $\alpha_{0}^{2}$ is chosen uniformly at random from $[0, 1]$ and…
NewUser2020
- 63
- 4
6
votes
1 answer
Error syndromes and recovery procedure in bit flip code
This question relates to exercise 10.4 in Nielsen and Chuang.
For syndrome diagnosis, the textbook provides an example where one has four projectors, by which, you can identify where a one qubit error has occurred. In this scheme, the syndrome…
Blackwidow
- 599
- 2
- 8
6
votes
1 answer
Implementation of Grover's Algorithm (minimum spanning tree)
I am trying to solve a minimum spanning tree problem using Grover's Algorithm. To accomplish this I would need to search a list for the minimum weight or edge for each point, for example:
Given the following list:
How would one use Grover's…
Maxwellsequations
- 75
- 3
6
votes
1 answer
Understanding a quantum algorithm to estimate inner products
While reading the paper "Compiling basic linear algebra subroutines for quantum computers", here, in the Appendix, the author/s have included a section on quantum inner product estimation.
Consider two vectors $x,y \in \mathbb{C}^n, x= (x_1, \dots…
IntegrateThis
- 545
- 4
- 14
6
votes
1 answer
IBM Q devices scheduling of gates with different durations
I was trying to figure out how scheduling works in IBM devices.
The thing that's bugging me is that in the quantum computer implementations I had seen before, the cycle concept is used. Say, for example, a cycle = 20ns. And all operations take that…
Kelthar
- 149
- 5
6
votes
1 answer
How to decompose a controlled unitary $C(U)$ operation where $U$ is a 2-qubit gate?
In the vein of this question, say I have a 2-qubit unitary gate $U$ which can be represented as a finite sequence of (say) single qubit gates, CNOTs, SWAPs, cXs, cYs and cZs. Now I need to implement a controlled-$U$ gate and hence need its…
Sanchayan Dutta
- 17,497
- 7
- 48
- 110
6
votes
1 answer
Defining qubit operator from scratch
I'm a beginner with Qiskit and the Python language at all.
Here is my question:
One of the VQE function arguments is qubit operator (qubitOp).
I saw some examples where the qubitOp object was produced by some already existing Qiskit module.
For…
Alex Tarantul
- 61
- 2
6
votes
3 answers
Why is the application of an oracle function not a measurement?
Why is the application of an oracle function not a measurement, causing the collapse of the system? How can you know the state of the system (the input of the oracle function) without measurement?
michiel perdeck
- 93
- 3
6
votes
1 answer
Physical qubit of optical quantum computer
I was researching how optical quantum computers work and discovered a KLM protocol that allows for building quantum gates using linear optics elements like mirrors, beam splitters, and phase shifters. However, I was wondering how would we get the…
Aleksandar Kostovic
- 327
- 1
- 5
6
votes
1 answer
Why do we use complex-conjugate instead of complex-conjugate-transpose when calculating the concurrence?
When we use the formula to calculate two-qubit entanglement, like these:
$$
C(\rho)=\max \left\{\sqrt{e_{1}}-\sqrt{e_{2}}-\sqrt{e_{3}}-\sqrt{e_{4}}, 0\right\}\tag{18}
$$
with the quantities $e_{i}\left(e_{1} \geq e_{2} \geq e_{3} \geq e_{4}\right)$…
karry
- 619
- 4
- 11