All Questions

Filter by
Sorted by
Tagged with
0 votes
0 answers
10 views

Quantum optimization and correlation function

If one imagines the nodes of the classical weighted graph as atoms, and paths between them as coupling strength, then to find the shortest path in the weighted graph, can one also look at the minima/...
Keane's user avatar
  • 1
0 votes
0 answers
24 views

is the main purpose of using Schmidt decompositon to visualize entanglement?

Is it correct to say that an entanglement state is entangled in any basis, but this fact may not be evident (like in the state $ \frac{1}{ 2} | 00 \rangle + \frac{1}{ 2}| 01 \rangle + \frac{1}{ 2}| 10 ...
Hadamard's user avatar
0 votes
0 answers
14 views

Product for block-encoding of two density operators

I know for density operator like $\rho$, we have a block-encoding matrix with purification operator and SWAP gate: $BE_{\rho} = \begin{bmatrix} \rho & \cdot \\ \cdot & \cdot \end{bmatrix}$. ...
Dan David's user avatar
0 votes
0 answers
24 views

Error on expectation value even with zero noise

If I use V2 fake backends, I can set a certain noise equal to 0 with backend.target['measure'][(0,)].error = 0 and I can do that for each kind of instruction ('id',...
stopper's user avatar
  • 373
0 votes
0 answers
53 views

How to determine the single-qubit phase?

In some works it is suggested to find the qubit phase by the following method: Apply $X/2$ (or $Y/2$) gate - preparing the qubit in superposition. Detune the qubit by flux pulse, for example here ...
Curious's user avatar
  • 249
0 votes
0 answers
6 views

Self referencing algorithms for multiplication of binary polynomials

Currently, I am going through the paper "Space-efficient quantum multiplication of polynomials for binary finite fields with sub-quadratic Toffoli gate count" by Iggy van Hoof. Two ...
Ash Ketchum's user avatar
0 votes
0 answers
8 views

Decrease noise of Fake Backends

I have the following code: ...
stopper's user avatar
  • 373
-3 votes
0 answers
23 views

The Quantum Mobility Quest - Airbus & BMW Group [closed]

Came across this article online and thought I'd share in case anyone was interested in registering, seems like a good opportunity but not quite for me right now. Airbus and BMW Group are launching a ...
geforfn's user avatar
1 vote
1 answer
25 views

Post selection during hook injection

I was reading the paper about "Cleaner magic states with hook injection"1, which is really cool, and I get technically, but it is unclear in which stages do you perform the post-selection. ...
Yaniv Kurman's user avatar
2 votes
1 answer
126 views

Questions on multi-controlled Toffolis and their implementation in Qiskit

Is it possible to decompose an $n$-controlled Toffoli into $O(n)$ CNOTs without extra working qubits? If so, is such an decomposition currently available in Qiskit or any other (preferably Python and ...
mavzolej's user avatar
  • 1,852
4 votes
0 answers
24 views

How do I calculate the expectation of the rational function, in the sense of the Haar measure?

I want to know the analytical solution of $\mathbb{E}_{\psi}\frac{\langle \psi |A|\psi\rangle}{\langle \psi |A^2|\psi\rangle}$. I see similar questions before approximate average, but it does not ...
Dan David's user avatar
1 vote
2 answers
48 views

Does the $\text{CNOT}$ gate activate if the control qubit is $-|1⟩?$

I understand how the $\text{CNOT}$ gate works intuitively: However, say we have a circuit where the $Z$ gate is applied to $|1⟩$, which turns $|1⟩ \to -|1⟩$. Then, there is a $\text{CNOT}$ gate with ...
Spike Spiegel's user avatar
1 vote
0 answers
20 views

How to actually solve for the eigenstates in the adiabatic version of Grover's algorithm

The adiabatic version of Grover's algorithm says that the eigenstates of the Hamiltonian $H(t)=(1-\frac{t}{T})H_0+\frac{t}{T}H_m$ (equation 10 in the linked paper) can be used to solve the eigenvalue ...
requiemman's user avatar
1 vote
1 answer
20 views

References for mapping qudit gates to qubits equivalent

Let's assume that I'm modelling a d-levels qudit as a set of n qubits, where $d = 2^n$. I would need to map the application of quantum gates on the qudit to a set of operations of the relative qubits ...
Frank's user avatar
  • 11
1 vote
0 answers
15 views

Can I get valid solution with HHL algorithm even if the QPE is not completely correct?

Can I get the valid solution of linear problem using HHL algorithm even if the QPE is not completely correct? My example is $A=diag(0.5, 0.2, 0.3, 0.6)$, so the solution is $[0.5, 0.2, 0.3, 0.6]$ ...
Nyyni's user avatar
  • 31
0 votes
0 answers
25 views

Deriving a equation in "Data re-uploading for a universal quantum classifier" paper: U(phi1,phi2,phi3) U(x1,x2,x3) = U(theta + w *x)

In "Data re-uploading for a universal quantum classifier" paper the U(phi1,phi2,phi3) U(x1,x2,x3) is derived as U(theta + w *x) in compact state. How to derive the above equation ?
Aakash's user avatar
  • 1
1 vote
0 answers
19 views

How can I initialize a classic register in qiskit?

is there a way to initialize a classic register in qiskit? I will go quickly through my problem and then suggest one solution but I am not satisfied with that and ask if there is another solution. ...
Qubii's user avatar
  • 171
2 votes
2 answers
33 views

How to estimate the negative amplitude of multiple qubits?

The probability of measurement is the square of amplitude. After measurement, how to guess the original amplitude of state?? For example, in linear problem, we would like to know the exact solution, ...
Nyyni's user avatar
  • 31
0 votes
1 answer
34 views

general way to decompose a CZ gate on $n$-qubit system

Suppose I have a CZ(i,j) gate (or CNOT) acting on qubit $i$ and $j$, on a $n$-qubit system. Is there a general way to decompose this gate into a set of gates that only involve single-qubit gates and ...
user185671631's user avatar
1 vote
1 answer
32 views

For arbitrary single-qubit unitary gate, does there exist a code such that the given gate is transversal?

Background Transversal gates are considered to be fault-tolerant logical operation as they won't lead to the propagation of local errors. Here are some examples: CSS code has transversal Pauli and ...
Yunzhe's user avatar
  • 300
0 votes
0 answers
36 views

Parallelize estimation of expectation values in Qiskit

Edit I tried using python multiprocessing library. The result with 8 cores isn't always faster than the original script that uses only one core. How can i improve the algorithm? Suppose i've a matrix ...
ar3q5dr9's user avatar
0 votes
0 answers
55 views

Can you push a CZ gate through a Toffoli gate?

Is it possible to push a CZ gate through a Toffoli gate?
Manuel's user avatar
  • 43
0 votes
1 answer
29 views

In Qiskit, no state vector after measure and reset

The code below doesn't work. I am looking for a workaround. OK, I can save the state vector as numpy array, recreate the whole circuit and initialize it thanks to this array. It works, but any simpler ...
Maurice Clerc's user avatar
0 votes
1 answer
17 views

Passing a book-keeping parameter to Qiskit Ibm Runtime Estimator

I have a Qiskit.QuantumCircuit object circ which prepares the state $| \Psi \rangle$, and a ...
squareroottwo's user avatar
0 votes
1 answer
56 views

Quantum Error Correction on a hexagonal lattice

I have an exercise in QEC, where I have given a hexagonal lattice with periodic boundary conditions (wrapped around a torus), with a qubit at each vertex. I have also given the Stabilizer generators $...
Ruebli's user avatar
  • 85
0 votes
0 answers
19 views

Implementing a Quantum Recurrent Neural Network

I want to implement a Quantum Recurrent Neural Network and use it for time series forecasting. As a starting point, I chose to implement it using the architecture given in this paper: https://arxiv....
MoBlufiz's user avatar
1 vote
0 answers
16 views

Specifying the image of a set of states under the action of a channel

I have a generic channel $\mathcal{N}$ acting on a subspace of states defined on a $d$-dimensional Hilbert space $\mathcal{H}$. I am trying to make a statement about the dimension of the image of that ...
forky40's user avatar
  • 6,143
0 votes
1 answer
64 views

If all terms of a local Hamiltonian commute, how hard is it to learn the ground state (energy)?

Suppose we have a $k$-local Hamiltonian with each of $m$ terms acting on $k$ of $n$ qudits of constant dimension $d$: $$H=H_1+H_2+\cdots+H_m.$$ If at least some of the terms don't commute, e.g., if $[...
Mark Spinelli's user avatar
0 votes
0 answers
24 views

How to 'quantize' a classical code?

I have a class written in Python: ...
Ash Ketchum's user avatar
0 votes
0 answers
23 views

Remove a register from a quantum circuit

I am trying to make a function like this in Qiskit: ...
Ash Ketchum's user avatar
1 vote
1 answer
810 views

Why can't Grover's algorithm apparently solve this simple situation?

I'm utilizing Grover's algorithm to solve a straightforward problem. It presents eight options, but only four are correct (the 1's in the S column) $$\begin{array}{c|c|c|c} q_0& q_1\ & q_2\ &...
Hadamard's user avatar
1 vote
2 answers
38 views

Access individual qubits of a quantum circuit in qiskit by qubit name

I am very new to quantum computing and only recently started learning Qiskit, so the question may sound a bit silly. Essentially, when I create a QuantumCircuit ...
Ash Ketchum's user avatar
1 vote
1 answer
33 views

Measuring one qubit in an entangled pair in another basis?

Qubits are usually measured in the computational basis, but we can change the basis by a unitary $U$ to measure in the basis formed by the columns of $U$. For example, if $| \psi \rangle = | 0 \rangle$...
Andrew Baker's user avatar
0 votes
0 answers
6 views

QISKIT Metal Saves Error Generating Python Code

Background I'm testing out the ability of the Metal GUI to save a simple circuit but it keeps generating code that gives rise to various errors. In the below code for example generates an error show ...
Shadow43375's user avatar
1 vote
1 answer
19 views

Is qiskit.pulse.SamplePulse deprecated?

I'm currently following along the book "Learn Quantum Computing with Python and IBM Quantum Experience" by Rodert Loredo and I am at chapter 8 - Generating pulse schedules on hardware. The ...
Johannes Jyrgenson's user avatar
1 vote
0 answers
11 views

Accuracy of QPE using histogram fit

In regular QPE, accuracy is $1/2^n$, where $n$ is estimation register size, and it is done with few shots and depth as $O(2^n)$ (total cost of $O(2^n*NumShots))=2^n=1/resolution$). I thought of the ...
Ron Cohen's user avatar
  • 1,184
1 vote
1 answer
31 views

What is the difference between shot and iteration of the quantum circuit?

Hi this question is stem from What is meant with "shot" in quantum computation?. If we just look for the distribution of the result, is there any theoretical difference between method 1 and ...
JYLEE's user avatar
  • 21
-2 votes
0 answers
27 views

ibmq belem noise model backend shows best result. why? [closed]

i run one circuit in presence of three basic backend noise model from this link https://qiskit.org/ecosystem/aer/apidocs/aer_noise.html ibmq belem, lima, quite, and fake provider noise model we used.....
Arpita's user avatar
  • 19
4 votes
0 answers
49 views

A measure of entanglement created by a unitary operation

Let $U$ be a unitary matrix acting on a 3-qubit system. If there is no correlation among any pairs of the three qubits, the unitary operation can be represented as $U = U_1 \otimes U_2 \otimes U_3$, ...
user185671631's user avatar
1 vote
0 answers
27 views

Get confused about the implementation of Amplitude Amplifier

I have a circuit $A$, which produces $$A|0^n\rangle _a |00\rangle _b = \phi_0 |00\rangle _b + \phi_1 |01\rangle _b+ \phi_2 |10\rangle _b + \phi_3 |11\rangle _b$$ And only $\phi_0 |00\rangle _b$ is ...
Alexis's user avatar
  • 183
3 votes
1 answer
77 views

What is the difference between classical-quantum and completely classical states?

States that are completly classical : $$ \begin{aligned} \tilde\rho_{A B} & =\sum_{x \in \mathcal{X}} \sum_{y \in \mathcal{Y}} p_{X, Y}(x, y)(|x\rangle \otimes|y\rangle)(\langle x| \otimes\langle ...
IamKnull's user avatar
  • 433
0 votes
0 answers
15 views

How to deal with unused qubits in application specific quantum chips?

Background I am a complete novice to quantum hardware but am trying to give myself an introduction to Qiskit Metal. I have set myself the challenge of designing a custom quantum chip for the Bernstein-...
Shadow43375's user avatar
2 votes
1 answer
124 views

Finding the "dual" basis of an overcomplete basis for Quantum State Tomography

This question is related to this stack exchange post: What does the POVM corresponding to single-qubit state tomography look like? From what I understand, when we are interested in reconstructing a ...
junoswrld's user avatar
1 vote
0 answers
43 views

Generalization of representing SU(2) as quaternions

I am familiar with the isomorphism between $SU(2)$ and the unit quaternions, and the group homomorphism from them to $SO(3)$. I am interested in knowing if there is a generalization for $SU(2^n)$. My ...
Chris Henson's user avatar
1 vote
2 answers
68 views

Why $\sqrt{\rho} = P \sqrt{\rho}$ in the proof of quantum error correction conditions in Nielsen & Chuang?

I have trouble understanding this proof in Nielsen & Chuang, specifically the identity in $(10.20)$, which reads $$ U_k^\dagger P_k F_l \sqrt{\rho} = U_k^\dagger P_k^\dagger P_k^\dagger F_l P \...
qntdni's user avatar
  • 13
0 votes
1 answer
53 views

Custom gate labels in PennyLane

I have a circuit with Rx gate, and I want to draw it with changed gate label. For example, instead of "RX" I want to have "custom_gate" written in the gate box. I have tried ...
Daniil Tarpanov's user avatar
0 votes
0 answers
9 views

Quantum Annealing on IBMQ using Qiskit-Pulse

Qiskit-Pulse is the analog level control SDK of IBMQ hardware. Is it possible to implement an adiabatic annealing protocol/algorithm on IBMQ hardware using Qiskit-Pulse? Not asking about QAOA, which I ...
The Quantum Enthusiast's user avatar
1 vote
1 answer
91 views

Problem with the mathematical definition of the eigenvalue algorithm on a specific exercise

I think I understand well how the eigenvalue algorithm works but when I try to define it mathematically I have problems. Specifically I have the matrix U: $$ U = \begin{pmatrix} 0 & i \\ i & 0 ...
Francescov20's user avatar
2 votes
1 answer
54 views

Why can't we do pure state tomography using interference with a known reference state?

I am new to quantum tomography, and right now I am trying to understand tomography with pure states. It's my understanding if we have the amplitude magnitudes as well as relative phases, we can ...
android_developer's user avatar
2 votes
1 answer
59 views

What does "lift" mean in the Lifted Product (LP) Code?

I am watching this talk about Lifted Product Code (LP). For me, it's quite straightforward to see how to construct a HyperGraph Product Code (HGP) using two separate classical codes. However, I failed ...
Yunzhe's user avatar
  • 300

15 30 50 per page
1
2 3 4 5
212