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From Qubo Hamiltonian to Ising Hamiltonian

I would like to convert my qubit hamiltonian fom the HeH+ system that I have obtained using Qiskit to an Ising or QUBO model. I have seen multiples examples from QUBO to Qubit Hamiltonian but on the ...
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0answers
11 views

Diamond distance and channel coding - connection?

Let us consider an encoder, noisy channel and decoder such that classical messages $m\in\mathcal{M}$ can be transmitted with some small error. That is, for a message $m$ that is sent by Alice, Bob ...
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0answers
11 views

How does the amplitude amplification in Grover's algorithm work?

As the question says - how does the amplitude amplification in Grover's algorithm work? I am fine with adding the negative phase on the winning state, but how does one generate the diffuser to ...
1
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2answers
28 views

How to derive $|0\rangle=\frac{1}{\sqrt{2}}(|+\rangle+|-\rangle)$?

When learning measurement basis, my teacher told us $|0\rangle=\frac{1}{\sqrt{2}}(|+\rangle+|-\rangle)$ and said that we can derive it ourselves. Along this, he also mentioned $|+\rangle=\frac{1}{\...
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1answer
14 views

How is eigendecomposition of a Hamiltonian equivalent to finding the minimum of an energy function?

This question is in regards to adiabatic quantum optimization which says we can minimize an energy function using adiabatic quantum computing. See e.g., this, this or any of the other articles ...
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1answer
18 views

Comparing complexity of digital and analog quantum computation

Complexity of an algorithm run on a digital quantum computer is quantified, roughly, by the number of elementary gates in the corresponding circuit. Can one similarly quantify the complexity of an ...
1
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2answers
24 views

Does QRNG generates True Random numbers?

I read an article that claims, QRNG can produce a true random number. So I wonder, how could they prove that this is a true random numbers generator? In fact, imagine I look at my memory state and ...
1
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1answer
20 views

Print runtime of an optimizer

I want to find the runtime of my program, i.e. the time it is in the quantum computer without queue time. However, I am using an optimizer so the code is a little different. ...
3
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1answer
23 views

What are QHT, QWT and QFT

I am new to quantum computing. I am not able to understand QHT, QWT and QFT. I tried searching for a suitable material but still could not find them. It would be great if someone can explain and also ...
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1answer
36 views

what should we add to complete the program

In the following code, what should replace #Your code here, if we want to create the quantum state $\frac{1}{\sqrt{2}}(|0\rangle - |1\rangle)$? (Hint: Think about ...
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1answer
26 views

This is a question about IBM quantum circuit used to generate the quantum cheque state

I'm learning about quantum cheque. And I read "Experimental realization of quantum cheque using a five-qubit quantum computer" which is written by Bikash K. Behera ,Anindita Banerjee and ...
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2answers
431 views

Is it true that the way we must program Quantum Computers is through Total functions only, if so why?

I have read that the way we must program Quantum Computers is through Total functions only. Why is this the case? Is it because quantum circuits are less forgiving in terms of logical errors? Could ...
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0answers
30 views

How do you debug the following code?

This is code provided by user47787 in response to my previous question: How to use backend.run() with a constant pulse shape in order to get the results of a measurement? When I run the following code,...
2
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1answer
26 views

Understanding polarizing beam splitters

I have been trying to understand this heralded CNOT gate on photons but I have some questions regarding polarizing beam splitters: The way I understand it, a PBS lets the photon through if the photon ...
1
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1answer
86 views

Qiskit CNOT-gate matrix mixup?

In the qiskit textbook chapter 1.3.1 "The CNOT-Gate" it says that the matrix representation on the right is the own corresponding to the circuit shown above, with q_0 being the control and ...
2
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1answer
54 views

How is a classical bipartite state written in quantum notation?

As in the title, is a classical bipartite state on $AA'$ given by $$\sum_{ij} p_{ij} \vert i\rangle\langle i\vert_A \otimes \vert j\rangle\langle j\vert_{A'}$$ with $\sum_{ij}p_{ij} = 1$. In ...
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1answer
26 views

How to use backend.run() with a constant pulse shape in order to get the results of a measurement?

I have formed a constant pulse and then I ran a measurement on the pulse. Now, I want to run a job to access the results of the measurement. Attached is a picture of the pulse and measurement. Now, at ...
0
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1answer
37 views

How to re-order logical qubit location into desired state?

Now, I'm studying about qubit mapping. When the mapping is done, the logical qubit will be randomly mapped to physical qubit. But I want to move the logical qubit location into desired state. For ...
2
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0answers
58 views

A way to check if entanglement is increased or decreased

I was wondering if there is a way to check if the amount of entanglement is increased or decreased after a quantum operation without calculating the actual value. That is, it does not concern with the ...
2
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1answer
31 views

Relation between Jordan-Wigner transformation and Hilbert-Schmidt inner product

Given a fermionic Hamiltonian in a matrix form, we can write it as a sum over Kronecker products of Pauli matrices using the Hilbert-Schmidt inner product. However if the same Hamiltonian is given in ...
2
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1answer
69 views

Initial state preparation for Hadamard test

I thought I understood Hadamard test but it seems to be shaky. I understand that to get the expectation value $\langle\psi\ | V^\dagger|{\bf Q}|V|\psi\rangle$ we need to have gate $V$ (in blue) below ...
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0answers
35 views

Applying a projector or a general nonunitary gate in the middle of a circuit using qiskit

Is there a way to implement a projector gate in a middle of a circuit?. For instance, assuming I have a Bell state $|00\rangle+|11\rangle$, I'd like to apply a projector on the first qubit onto state $...
2
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2answers
88 views

Initial state for QAOA

I'm learning about QAOA and I got curious about how they choose initial state. They somehow decided to choose initial state as equal superposition of all possible state and I wonder that there is any ...
1
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1answer
54 views

How do you change the backend.run() command?

This is code from Chapter 6.1 of the qiskit textbook, which shows a job being run. How would you change the first line of the backend.run() command, the schedules parameter, in order to use it for a ...
1
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1answer
33 views

Integer factorization using Shor's Alorithm

I have question about Shor's algorithm, from I know it's for factorize an integer and can factorize big number with ease. I using Qiskit to try make a simple factorization program (with local ...
1
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1answer
31 views

Increasing entropy for projective LCPT mapping

Given a set of projectors $\{P_i\}$ acting on a space $\mathcal H_S$, let $\Phi$ be the LCPT map defined by $$\Phi(\rho)=\sum_i P_i\rho P_i.$$ The goal is to show that $S(\Phi(\rho))\ge S(\rho)$. The ...
1
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1answer
31 views

Vector math of applying an X-gate on an $|i\rangle$ basis state

It is well known that the X-gate will apply a rotation about the x-axis on the bloch sphere. Knowing this, the $|i\rangle$ state should be converted to the $|-i\rangle$ state on the application of ...
2
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1answer
29 views

Comparing technical limitations of major quantum computing approaches

As far as I know, major quantum computing approaches include superconducting qubits, trapped ions, nuclear magnetic resonance qubits, and free space quantum optics. I guess two main technical ...
2
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1answer
58 views

Prove the subadditivity for the von Neumann entropy of a bipartite state

I want to prove the subadditivity relation $S(\rho_{AB})\le S(\rho_A)+S(\rho_B)$ for the Von Neumann entropy. The tip is to use the Klein inequality $S(\rho_{AB}\Vert \rho_A\otimes \rho_B)\ge 0$: $$S(\...
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1answer
37 views

Faster pulse generation in Qiskit

I need to be able to generate very quickly pulse schedules to submit them on quantum chips. For the moment I am generating instances of QuantumCircuit: ...
1
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0answers
32 views

Transform Fermionic operators to quantum circuit in qiskit

I am trying to realize a modified version of the UCCSD algorithm, which consists of combining multiple fermionic opeators to form a unitary tranformation U to act ...
2
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0answers
64 views

How to prove that the mutual information is subadditive?

Let $\mathbf x=(x_1,...,x_n)$ and $\mathbf y=(y_1,...,y_n)$ be two vectors of random variables. To make things concrete, assume that Alice sends each component $x_j$ through a noisy channel to Bob, ...
1
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1answer
101 views

How to generate a quantum circuit from the quantum state $|1000\rangle+|0100\rangle+|0010\rangle+|0001\rangle$?

I am trying to understand the steps of how make a state preparation circuit from a quantum state. For making my question more clearer, for example, for the state is $\frac{|00\rangle+|11\rangle}{\...
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1answer
35 views

How to re-ordering physical qubit location into desired one?

Suppose original quantum circuit have 4 qubits and some quantum operation. Also suppose the result of original quantum circuit state is '1100'. Then apply qubit mapping then mapping state is like ...
2
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0answers
47 views

Implement a projection operator as a quantum circuit

Let the state $|\Psi\rangle\equiv a|0\rangle\otimes|\psi_0\rangle + b|1\rangle\otimes|\psi_1\rangle$, where $|\psi_0\rangle$ and $\psi_1\rangle$ belong to a multi-qubit register $R$ and the ...
2
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0answers
82 views

Is there an efficient quantum circuit that create a random permuntation matrix?

Suppose we want to generate a random, random according to some probability distribution, unitary permutation matrix that is applied to an input of $n$ qubits. So is there an efficient polynomial time ...
1
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1answer
66 views

Why is the quantum volume vastly greater than the number of qubits squared?

According to Wikipedia, the Honeywell computer has quantum volume ("QV") equal to 1024 and has 10 qubits. QV should not be more than $n^2$ squared, i.e. 100. Is this any math error? Are the ...
2
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2answers
86 views

What are the constraints for the coefficents of the basis states in quantum computing?

$\newcommand{\ket}[1]{\left|#1\right>}$ It's known that the Kolmogorov axioms characterise a probability distribution: Probability of an event is a non-negative real number. The sum of all ...
2
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1answer
52 views

How to Implement a noisy identity gate on qiskit?

I can successfully implement the U gate (single qubit) on qiskit, but when I am trying for the identity operation it is not showing any differences with the ideal one .
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1answer
30 views

Matplotlib graphs are being duplicated each time

Simple UI question. I have installed qiskit according to the instruction and try to implement some basic operations. I have the issue that anything I plot appears twice. I am not sure why this is ...
6
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0answers
57 views

How does the extremality of a POVM reflect on its Naimark dilation isometry?

Let $\mu:\Sigma\to\mathrm{Pos}(\mathcal X)$ be some POVM, with $\Sigma$ the finite set of possible outcomes, and $\mathrm{Pos}(\mathcal X)$ the set of positive semidefinite operators on a finite-...
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2answers
42 views

How does one even get started in Quantum Computing, specifically building qApps? [closed]

I want to build a quantum application, qApp if you will; how does one go about figuring out the right use-case and best framework to turn to, to start building these things? Quantum REPL? How do I ...
1
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1answer
37 views

Job ids retrieval from ID. Big set of jobs

I'm in the need of running a lot of jobs in the IBM backends. If one likes to run in parallel two jobs (say, with two different parameters), I have seen in the Jobs ...
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2answers
73 views

Tensor product and Dirac notation

Can someone shows me how to proof this equality: $\frac{1}{\sqrt2}(\alpha|000⟩+\alpha|011⟩ + \beta|100⟩ + \beta|111⟩ )$ = $ \frac{1}{2\sqrt2}[(|00⟩+|11⟩) \otimes (\alpha|0⟩+\beta|1⟩) + (|01⟩+|10⟩) \...
1
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2answers
53 views

Is ($|+⟩$$⟨0|$ + $|-⟩$$⟨1|$ ) similar to ($|0⟩$$⟨+|$ + $|1⟩$$⟨-|$ )?

Is ($|+⟩$$⟨0|$ + $|-⟩$$⟨1|$ ) similar to ($|0⟩$$⟨+|$ + $|1⟩$$⟨-|$ ) ? Can we just reversed it this way when doing Dirac manipulation? I try to calculate HZH = X and i need to reverse the second H
1
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1answer
77 views

How to normalise when the probability of measurement is zero?

In one of the answers to this question on measuring one qubit it is explained that given a general two-qubit state $$ |\psi\rangle = \begin{bmatrix} \alpha_{00} \\ \alpha_{01} \\ \alpha_{10} \\ \...
1
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1answer
29 views

Question about the counter diabatic(CD) term in Digitized Adiabatic Quantum Computing

Recently I have read two articles about the Digitized Adiabatic Quantum Computing(DAQC), and tried to factorize $35=5\times7$ and $2479=67\times37$. But some problems came when trying to solve the ...
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0answers
43 views

How to determine the direction of arrows on a Bloch sphere from a vector/ket representation?

The following graphs contain the vector/ket representation of the vector on the bloch sphere. I don't understand how to determine the position of the vector on the bloch sphere based on those vector/...
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0answers
16 views

Efficient simulation of linearly assembled Quantum States

In this paper section 4.2 the author describes how to efficiently simulate linearly assembled quantum states. When describing the procedure to do so the author shows the following circuit: The ...
2
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2answers
681 views

Why do we have to measure the circuit before sending it to the real quantum computer?

If I want to run a circuit on a real quantum computer, I have to measure it before running it. For example: ...

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