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How can I implement an arbitrary quantum channel in a quantum circuit for real experiments using IBM quantum experience?

Let's suppose I have a quantum channel given in the Kraus decomposition $T(\rho) = \sum_{i} K_i \rho K_i^{\dagger} $ is there any way to put explicitly these $K_i$ in IBM quantum experience (QE) to ...
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1answer
9 views

Rotation of multi-body interaction in quantum circuit

In quantum circuit, how do you implement the rotation of multi-body interaction, such as $e^{-i\theta\sigma_z^1\sigma_z^2\sigma_z^3}$? I already know the case of less than two-body interaction, but I ...
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0answers
16 views

Shifting amplitude from one basis to another with a control qubit

I was reading a forum where people were talking about a proposed quantum algorithm that solves an NP-complete problem in polynomial time. The algorithm appears to have flaws (after all, none of you ...
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2answers
22 views

Qiskit unitary representation seems shifted

I have implemented a simple CNOT gate using qiskit I was expecting a the result the matrix as in the following image (extracted from wikipedia): ...
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0answers
11 views

What is Ising Hamiltonian ? What its role in Portfolio Diversification?

I am asking this question with reference to this https://github.com/Qiskit/qiskit-iqx-tutorials/blob/master/qiskit/advanced/aqua/finance/optimization/portfolio_diversification.ipynb Happy to know new ...
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1answer
15 views

What does it look like to split an EPR pair?

I am reading Quantum Computation and Quantum Information by Michael A. Nielsen & Isaac L. Chuang, and I am confused about a concept presented in Section 1.3.7: Quantum Teleportation. The book ...
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1answer
30 views

In the context of Quantum theory of Information, Typical eigenvectors are permutations of basis vectors. Why?

Why is this so? Can someone please give me detailed steps with an explanation?
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24 views

Can't load account on IBM's qiskit

The command load account keeps giving the warning that it can't find a QConfig file. A search for the error message brings me to an answered question. However, this solution also doesn't work, ...
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0answers
23 views

How qubit phase is build in real hardware?

How qubit phase is build in real hardware? On IBM Quantum, D-Wave, etc?
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0answers
17 views

Repeating Quantum Phase Estimation algorithm

In the Quantum Recommendation Systems paper, the authors use the Quantum Phase Estimation algorithm in a way that is slightly different from what I've seen so far. This is how it is described: The ...
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0answers
37 views

If one had a verifiable solution to P versus NP problem, how, and why, would one go about submitting it?

Asking for a friend. The exclusivity/elitism of the field (and the dominance-human hierarchy), as well as the outcomes of "exploitation of "discoveries" throughout history have friend leaning away ...
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1answer
15 views

Why is the number of qubits linear in the inverse of epsilon in Quantum Phase Estimation?

On Wikipedia, one can read the following about Quantum Phase Estimation: the algorithm estimates the value of $\theta$ with high probability within additive error $\varepsilon$, using $O(1/\...
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0answers
37 views

Matrix mod 2 multiplication

There was a similar question asked here, but I feel like mine is even more basic. What's the easiest way to implement a circuit $U$ corresponding to matrix multiplication modulo 2? $$ |x_1x_2x_3\...
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1answer
41 views

Does principle of deffered measurement imply information can travel faster than light?

I have been reading the book by Michael A Nielsen and Isaac Chuang and came across the principle of deferred measurement. They showed using this principle how the circuit for quantum teleportation can ...
3
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1answer
159 views

Does Controlled-U gate entangle qubits?

I've read C-NOT gate entangles qubits, but is it only for C-NOT or any arbitrary CU gate (apart from the likes if CI) entangles qubits?
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0answers
26 views

Qiskit not installing properly on pyCharm CE

I have installed qiskit through my terminal using pip3 install qiskit. But when I try to import all from it in my coding software, it returns a M...
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1answer
44 views

I made a simple circuit on qiskit,but I have some question on this result

I made a simple circuit that we can see. In my view, $|00000\rangle$ should appear in one result, but I didn't see it. why?
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1answer
25 views

QML: “Quantum Data loader” instead of QRAM?

In last year‘s conference "Quantum For Business 2019" Iordanis Kerenidis gave a nice talk about quantum machine learning. At about time 27:10 he mentions a "Quantum Data loader" as an alternativ for ...
4
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1answer
66 views

Represent a pure state in terms of 2 antipodal points on the Bloch sphere

I recently had an assignment where the question is based on the assumption that we can write any pure state qubit $|\phi \rangle$ as: $$|\phi \rangle = \gamma |\psi\rangle + \delta |\psi^\perp ...
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0answers
24 views

Decomposing Hamiltonian into qubit model representation

One of the main application of VQE is its application to find the approximation to the ground state energy (smallest eigenvalue) for a particular molecule through an iterative method. To be able to ...
3
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1answer
46 views

$H = e^{i\pi/4} \sqrt{iNOT}$?

In the paper Valley qubit in Gated MoS$_2$ monolayer quantum dot, a description of how a $NOT$ gate would be performed on a qubit in the described device is given. The authors say that in the ...
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1answer
13 views

Error parameters from Qiskit backends

In order to build a custom noise model in Qiskit Aer, I requested the error parameters from different backends and got 3 (9) parameters for each single-qubit (two-qubit) gate as output. However, I ...
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1answer
21 views

Placement of quantum circuits

I have a question concerning the placement of quantum circuits on Google devices. Consider the following code: ...
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0answers
19 views

What does the maximum of a Hamiltonian means (in a particular paper)?

In the paper Quantum Observables for continuous control of the Quantum Approximate Optimization Algorithm via Reinforcement Learning, an Hamiltonian is defined in order to solve the MAXCUT problem : $...
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1answer
63 views

Trying to use matrices for Hadamard and Controlled Not gates

I have the following simple quantum circuit: This outputs are 00 and 11 for the two qubits. Using matrices, I have applied the H gate to the first qubit (ket 0): $\frac{1}{\sqrt{2}}\begin{pmatrix}1&...
2
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1answer
64 views

Problem with controlled rotation in HHL

In HHL algorithm, for subroutine involving controlled rotation, after applying $R_y(\theta)$, where $\theta=\frac{2C}{\lambda}$ to the ancilla, the state changes to $\sqrt{1-\frac{C^2}{\lambda^2}}|0\...
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1answer
32 views

It two unitaries are delta apart in trace norm, then what is the trace norm of outputs states when the same input state is applied to two unitaries?

Suppose we are given two unitary matrices $U$ and $V$, with the following guarantee, $$||U - V||_1 \geqslant \delta$$ for some $\delta \geqslant 0$. We apply an input density state $\rho$ ...
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1answer
27 views

Find local state and compute Bloch coordinates, like Quirk

In a multi-qubit system I can find the amplitudes of a state and compute probabilities, $\theta$, and $\varphi$. This falls out from simulation with simple numpy arrays. For example, after application ...
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2answers
31 views

How to perform operations like sin over Qiskit parameters

I want to create a parameter dependent gate in qiskit and I need to compute some complex operations as sympy.atan2 or sympy.sin ...
3
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2answers
35 views

How to implement exponentiation of a gate without breaking complexity?

In the application of QFT for quantum phase estimation (QPE) of a unitary $\mathbf{U}$, one has to perform successive controlled operations using powers of $\mathbf{U}$. In order not to break the ...
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1answer
24 views

$\lambda$ parameter for U3 gate in qiskit Bloch sphere visualisation

It is easy to see how $\theta$ (rotation from the positive z-axis) and $\varphi$ (rotation from the positive z-axis) affect the initial state of the qubit when looking at the Bloch sphere but I have ...
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0answers
26 views

Finding minimum with Grover

I am a beginner in quantum computing. I have already computed the sat quantum solver with Grover search and then, I would like to compute the "minimum search" of Dür and Hoyer. My question is: Is it ...
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1answer
28 views

Qiskit - Z expectation value from counts?

For a given state $|\psi\rangle$, how would I work out $\langle\psi|Z|\psi\rangle$ ? If I run a quantum circuit and get the counts dictionary on qiskit, I get observables in the Z basis. For n=1 ...
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1answer
18 views

Is there quantum error correction code package for python

I'm working on the development of a new quantum error correction protocol that tries to maximize the coherence of the qubit. Is there a package for python, similar to qutip, that could help me in this ...
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0answers
12 views

How to get the $T1$ specs for the Rigetti's quantum processor (Aspen 7)

I am trying to find the $T1$ coherence time for different qubits of Rigetti's quantum processor (Aspen 7) using Python. I tried using Specs() but encountered an ...
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0answers
4 views

Where does the energy going in a Power Rabi experiment with superconducting circuits?

When performing a Power-Rabi experiment, e.g in superconducting circuits, we are playing a pulse to a qubit and then reading out its state by playing another pulse to a dispersively-coupled readout ...
1
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1answer
39 views

Topological quantum computer and two dimensional materials

Recently I read thread on topological quantum computers. If I understood correctly, gates in such computers are based on "effects" in two dimensional spaces. Since our space is three dimensional, such ...
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0answers
18 views

Quantum circuit CCX optimization for Grover

I am working on a circuit for a Grover problem and during that I am trying to minimize the used QuBits. The problem is shown in the attached image. In this case the circuit is more or less efficient ...
1
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1answer
38 views

Need some help with Purity calculation

maybe you could help me a little about my calculation of a quantum pure state with purification. I have this density matrix: \begin{equation} \rho= \begin{pmatrix} 0.4489 & 0.2304 & 0.2162 &...
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0answers
35 views

Not sure what do Nielsen and Chuang mean by number of operations

I am reading Nielsen and Chuang's "Quantum Computation and Quantum Information". One important concept about algorithms is how the number of operations scales with the length of the input. I realized ...
2
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1answer
76 views

What does the notation $U(B,\beta) = \prod_{j =1}^n e^{-i \beta \sigma_j^x} $ mean in the context of QAOA?

In the article Quantum Observables for continuous control of the Quantum Approximate Optimization Algorithm via Reinforcement Learning, the following notation is used to describe an Unitary operation ...
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2answers
51 views

Problem with commutation of $e^{-iH_1t}$ and $e^{-iH_2t}$, where $H_1$ commutes with $H_2$

I'm given with a Hamiltonian, $H=H_1+H_2$, where $H_1=\sigma_x\otimes\sigma_z$ and $H_2=\sigma_y\otimes\sigma_y$, and want to built a circuit which will implement $e^{-iHt},t=\pi/6$. We see that as $\...
2
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1answer
35 views

In Google's Quantum Supremacy experiment, what if we use $\theta=45°$ for two-qubit $f_{sim}$ gates?

In Google's Quantum Supremacy experiment, they use $f_{sim}$(fermionic-simulation) gates with $\theta=90°$ and $\phi=30°$ as their two-qubit gates. What if we use $\theta=45°$ for the two-qubit $f_{...
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2answers
38 views

How to switch bit in the quantum state?

I want to transform binary representation from one to other. Here, I have 2 registers one act as control register and another is target register with the same number of qubits $n$. Consider $n = 3$ ...
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0answers
24 views

Why Alice and Bob don't get the same result when they measure in the same basis?

I'm simulating the BB84 protocol using simulaqron. My problem is that when Alice and Bob measure in the same basis, they don't get the same result. How can I fix this error? . BB84.py ...
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1answer
51 views

How are the two states factored out of Deutsch's circuit?

After placing the Hadamards on the 2 qubits (both initialized in the $|1\rangle$ state) in the circuit, we are given: $ |\psi_{b}\rangle = \frac{1}{2}(|0_{1}0_{2}\rangle -|1_{1}0_{2}\rangle -|0_{1}...
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2answers
66 views

Gate Y returns wrong phase in IBM's circuit composer

One can check that, with IBM's circuit composer, $Y$ gate acted on $|0\rangle$ or on $|1\rangle$ returns the same phase of $\pi/2$. Is this a bug?
1
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1answer
63 views

Real backend for my students?

I'd like each of my students to run at least one program (however trivial) on a real quantum computer. They can each sign up for accounts on ibm-q-experience. The question is, which of the backends ...
2
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1answer
29 views

Why does not ibm-q-experience transpile a circuit always in the same way?

When I run a certain circuit (using several qubits, it is not a very simple one) in IBM quantum experience, I find that sometimes it is transpiled in one way and sometimes in another. And the final ...
2
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1answer
42 views

What does the notation $\sigma_j^z$ mean for Pauli matrices?

In multiples papers or online article on the QAOA algorithm (such as this one), I found notation for the Hamiltonian similar to this one : $$ \sum_{ij} \frac{1}{2} (I-\sigma_i^z \sigma_j^z)$$ I don'...

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