Questions tagged [vqe]

For questions about the Variational Quantum Eigensolver, a quantum/classical hybrid algorithm that can be used to find eigenvalues of a (often large) matrix H. When this algorithm is used in quantum simulations, H is typically the Hamiltonian of some system. In this hybrid algorithm, a quantum subroutine is run inside of a classical optimization loop.

Filter by
Sorted by
Tagged with
2 votes
1 answer
64 views

Implementing cphase gate on IonQ through Amazon Braket

I am implementing a VQE algorithm where I need controlled phase gate as part of ansatz circuit. I am using Amazon Braket service. Ionq processor however does not support c-phase gate or phase gate. ...
F1_light's user avatar
-2 votes
0 answers
60 views

How to solve an optimization problem that includes "continuous" variables with constrains using QAOA/VQE?

Here is the code from the previous question I asked on the same topic: How to solve quadratic programming problems with continuous variables and continuous constraints by using quantum algorithms? ...
said zhn's user avatar
1 vote
1 answer
36 views

Getting a numeric result from the variational quantum eigensolver

I am confused about how the VQE is able to print out a decimal number for the ground state energy of a molecule. For example, for $\text{LiH}$, the ground state energy I get for an interatomic ...
Angel Martinez's user avatar
1 vote
0 answers
20 views

Why is quantum annealing not used in optimization for variational quantum algorithms?

I have been learning about variational quantum algorithms and encountered that none of the articles talk about using quantum annealers for optimization of the parameters ? I have however encountered ...
Chetan Waghela's user avatar
1 vote
1 answer
70 views

Need help regarding building a custom VQE

I want to write code for a custom Variational Quantum Eigensolver (VQE) capable of computing eigenvalue(s) for non-Hermitian systems, based on this paper. I have formulated a cost function (provided ...
Bravyi's user avatar
  • 11
2 votes
0 answers
19 views

Understanding the Role of Qiskit's VQE Code in Light of Pre-calculated Zero-Point Vibrational Energy in Gaussian Files

In the context of quantum computational chemistry, the Qiskit VQE (Variational Quantum Eigensolver) code is often used to calculate the vibrational energies of molecules, including the zero-point ...
Akash Yadav's user avatar
3 votes
0 answers
44 views

How to update angles

I am struggling to understand the concept of updating angles in a parameterized algorithm. Assume I have an objective function $x^2+1$ that I want to optimize using QAOA which can handle continuous ...
34341's user avatar
  • 31
5 votes
2 answers
171 views

Why is it hard to prove complexity bounds for variational algorithms?

I'm not very familiar with variational algorithms, but I've heard people say that they're "heuristic" and it's difficult to measure their performance via complexity analysis. Why is this the ...
BQPcomplete's user avatar
1 vote
1 answer
71 views

Is Qiskit's Estimator Primitive running PauliStrings in Parallel?

I am trying to run the following code: ...
QuantumTheoretical's user avatar
2 votes
0 answers
34 views

Qiskit noisy FakeManila simulator + ZNE

I am trying to run a simple VQE calculation on H2 using FakeManila noise model and ZNE for error mitigation; see code below. The problem is that I can never reach not even close the ground electronic ...
Carlos Murilo Romero Rocha's user avatar
4 votes
0 answers
105 views

Variational Quantum Eigensolver (VQE) by scipy minimize in cirq does not work

I tried to make a cirq program calculating an eigenvalue of the observable by VQE. Inspired by the qulacs VQE tutorial, I defined a cost function from the expectation value of the observable with ...
Weongyu Lee's user avatar
2 votes
0 answers
57 views

Efficient gate executing the time evolution of a Hamiltonian using Runge-Kutta method

You can find a minimal working example below. In particular, I want to replace the scipy.linalg.expm() matrix exponential by a Runge Kutta time evolution method as ...
ANDREAS kruckenhauser's user avatar
1 vote
0 answers
58 views

Help me to find error in finding Cost Function for SSVQE algorithm [closed]

Q: Build SSVQE's cost function using the following observable: $$O=2II−2XX+3YY−3ZZ\,.$$ This cost function should take in parameters as input. Use the included variational form, with reference states $...
Kishore's user avatar
  • 11
2 votes
1 answer
153 views

Knapsack problem formulation

I would like to use a knapsack problem formulation based on Lucas paper. Namely, I try to implement the following math formula for Hamiltonian $H =H_A + H_B$, where $$H_{B} = -B\sum_{i=1}^{n}v_{i}x_{i}...
JackAW's user avatar
  • 21
3 votes
2 answers
156 views

The importance of the ansatz in VQE algorithm

Let's say I have a universal quantum computer that can perform anything. In this case, any VQE algorithm can use any operation, so no ansatz is needed to implement it. My question is, is the usage of ...
Alex's user avatar
  • 81
1 vote
1 answer
59 views

Pennylane variational classifier demo - need for padding

In the variational classifier demo from Pennylane, the data loading is performed with ...
Sarvapriya Tripathi's user avatar
4 votes
0 answers
65 views

Ansatz for VQE demonstrating Quantum Advantage

What would be a possible ansatz quantum state in VQE (variational quantum eigensolver [1]) that would demonstrate the quantum advantage of VQE over classic computers? More specifically, I see that VQE ...
user20374's user avatar
4 votes
0 answers
51 views

Difference between Qiskit and Openfermion two body integrals

I am struggling with understanding the differences between OpenFermion and Qiskit libraries when it comes to Molecular Data, two body integrals. For example, I am working with the following ...
Eugen's user avatar
  • 41
3 votes
0 answers
86 views

Minimum working example for Qiskit's AdaptVQE

I am trying to implement a simple AdaptVQE in Qiskit. Following the documentation provided by Qiskit, this should be very simple: ...
NaturalLog's user avatar
0 votes
0 answers
27 views

Does ScipyImaginaryEvolver in qiskit work independently of ansatz and parameters?

I am solving a Hamiltonian using imaginary time evolution and I tried it with VarQITE and ScipyImaginaryEvolver available in qiskit. I created a custom ansatz so that the evolved state revolves only ...
Cheshta Joshi's user avatar
4 votes
2 answers
124 views

Is there a way I can create an ansatz such that the number of 1 is same in all the superposition states? [duplicate]

So I am working with a variational quantum algorithm and I realised that it would be very beneficial if I could create an ansatz where all the states in the superposition have same numbers of 1s. For ...
Cheshta Joshi's user avatar
0 votes
0 answers
55 views

Compute molecular vibrational energy of CO2 molecule using VQE

I have to compute the molecular vibrational energy of CO2 molecules using VQE, but I am not progressing; Code on the qiskit website does not work. Does anyone have any working code to find vibrational ...
Akash Yadav's user avatar
1 vote
0 answers
24 views

Is there a way to find the computational resources required to perform a simulation of n- qubits in Cirq similar to qsim?

I’m trying to model basic spin chains in 1D using VQE (ideal circuit) with cirq and qsim. The models have between 10-20 sites and varying interactions (nearest neighbour, next to nearest neighbour etc)...
lake_apricot's user avatar
1 vote
0 answers
36 views

Efficient classical simulation technique to execute this specific quantum circuit

I have a quantum circuit similar to the ones used in VQE methods. One difference is that the angles of the $R_y$ rotations are limited in the range $[0, 0.2]$ (and chosen randomly). In my case, I have ...
stopper's user avatar
  • 393
1 vote
0 answers
86 views

VQE for Vibrational ground state energy

I was reading this article. In this article, they calculated the vibrational energy of CO2 and NH3 molecules using VQE, and I checked qiskit documentation for finding Vibrational energy using qiskit. ...
Akash Yadav's user avatar
0 votes
1 answer
31 views

Recovering phases in $2n$-bit binary representation of n-qubit Paulis

I am currently going through a paper discussing Pauli sampling strategies for VQE: https://arxiv.org/abs/1908.06942 I want to code and test their strategy. They explain how to create a circuit ...
Saturnin's user avatar
1 vote
0 answers
59 views

Ground state returned by VQE is not an eigenstate?

With my VQE algorithm, I want to obtain both the ground state energy and its corresponding ground eigenstate. However, the state I reach using VQE is usually very different from the true ground ...
user22395's user avatar
1 vote
2 answers
194 views

Where can I find tutorials on quantum variational algorithms?

I am interested in learning about quantum algorithms, especially quantum variational algorithms. I would like to know where I can find resources that delve into specific quantum variational algorithms ...
rexy london's user avatar
3 votes
1 answer
292 views

How does VQE work?

Here is the VQE overview from Peruzzo et al. 2013 I am trying to understand in detail how each step works, assuming at first one qubit and a Hamiltonian of the form: \begin{equation}\tag{1} H = \...
deb2014's user avatar
  • 111
0 votes
1 answer
38 views

Creating a parameterized Operator in Qiskit that cannot be decomposed into Qiskit supported gates

I am trying to create a custom ansatz to use the built-in Qiskit VQE() function. My ansatz is composed of single qubit gates and a hamiltonian gate which cannot be decomposed into Qiskit supported ...
user22395's user avatar
5 votes
1 answer
103 views

Recent experimental demonstrations of variational quantum algorithms?

I am interested in the recent experimental demonstrations of variational quantum algorithms. Can someone please provide me with a list of references of recent experimental demonstrations of ...
Soumik Adhikary's user avatar
0 votes
3 answers
317 views

How to represent Beam-Splitter and Kerr gates as basic quantum logic gates?

I want to know how to convert these exponential forms to tensor products of well known logic gates (like the ones built into Qiskit). My goal is to program the Beam-splitter-Kerr ansatz circuit for ...
user22395's user avatar
4 votes
2 answers
202 views

Does the gradient commute with the partial trace?

Suppose I have a parameterized quantum state: $\rho(\theta) = U(\theta) \rho U^\dagger(\theta)$. I am curious to know whether the following holds: $\frac{\partial \text{Tr}_A (\rho(\theta))}{\partial \...
Jon Megan's user avatar
  • 497
0 votes
1 answer
105 views

How the number of function evaluations is calculated in Qiskit when running VQE

I want to understand how the number of function evaluation is calculated by Qiskit when running VQE algorithms. Here is some code I used in order to test this: ...
Radu M.'s user avatar
  • 218
0 votes
0 answers
50 views

N-qubit VQE ansatz to generate all states?

I have found ansatzes that generate every state for certain specific values of n. However, I want to be able to write a function where I can pass in a value n (number of qubits) and be returned an ...
user22395's user avatar
0 votes
0 answers
23 views

How can i get the superposition of 8 bits from 26 bits outputs in qiskit

the only idea i see is get state vector from density_matrix for example, i have the circult: ...
qin guang's user avatar
2 votes
1 answer
78 views

SPSA: maxiter (int) – The maximum number of iterations. Note that this is not the maximal number of function evaluations

This is from classical optimization algo. used for VQE. May I know what is the difference between maxiter and the number of function evaluation difference?
chetan waghmare's user avatar
2 votes
1 answer
437 views

How grouping of Pauli strings is handled in Qiskit when running VQE?

When performing a VQE algorithm, the electronic problem Hamiltonian of the physical system under study needs to be mapped to a qubit Hamiltonian written as a sum of tensor products of Pauli operators (...
Radu M.'s user avatar
  • 218
0 votes
1 answer
171 views

How to assign new parameters to an existing quantum circuit?

Say I have a quantum circuit like this This is an ansatz for solving linear equation provided in the Qiskit's textbook In the textbook, it was shown how to find the optimal parameters of this ansatz ...
Vaishnav's user avatar
0 votes
0 answers
112 views

Combinatorial optimization problems solving using VQE

I'm studying about the variational quantum algorithms and I would like to know about the usage of VQE for solving combinatorial optimization problems. VQE can find the ground state energy of a given ...
William's user avatar
  • 151
2 votes
2 answers
155 views

Simplest 2-site VQE Ansatz to generate all states?

For 1-site I was able to use an Rx gate followed by an Ry gate to generate every possible state. For two-sites, I initially tried to apply this to each qubit but realized this doesn't work because it ...
user22395's user avatar
0 votes
1 answer
229 views

Error when importing qiskit_nature.algorithms.(GroundStateEigensolver, NumPyMinimumEigensolverFactory)

I'm trying to import the following elements: from qiskit_nature.algorithms import (GroundStateEigensolver, NumPyMinimumEigensolverFactory) But it shows the error: AttributeError: module 'sklearn....
劉承瀚's user avatar
0 votes
1 answer
81 views

BOBYQA optimizer IndexError

I'm trying to implement BOBYQA optimizer for my VQE job. Though, I'm facing the below issue. Can anyone help in pointing out what the actual cause of this issue is and how to solve this: ...
Amey Meher's user avatar
1 vote
1 answer
97 views

Only use the specific parameters (angles) in variational quantum eigensolver

I’m following the tutorial (https://qiskit.org/textbook/ch-applications/vqe-molecules.html) to construct the VQE circuit. In this tutorial, it used the classical optimizer like “COBYLA, SPSA, SLSQP” ...
劉承瀚's user avatar
4 votes
1 answer
295 views

What is the expectation value for the ground state of $ H = \sum_i Z_i Z_{i+1} + \sum_i X_i $?

What is the expectation value for the ground state of $ H = \sum_i Z_i Z_{i+1} + \sum_i X_i $ ? In Eq. 15b this provides a solution in k space. The minimum would be reached for $E = -4$. But for ...
user18722294's user avatar
0 votes
1 answer
195 views

Remove Orbitals in FreezeCoreTransformer (qiskit)

In Qiskit's VQE tutorial, the FreezeCoreTransformer is used and some orbitals are removed. In the particular case of LiH, they remove [-2,-3] orbitals. Why are the orbitals indexed in this way? How ...
Maria Gabriela Oliveira's user avatar
1 vote
1 answer
231 views

Commutativity of XY gate

My question is a simple one: Can 2 XY gates commute ? XY gate is a 2-qubit XX+YY interaction also sometimes referred to as iSwap gate.
Marouane Jaakik's user avatar
3 votes
2 answers
222 views

How to derive quantum advantages for VQAs, if the underlying classical optimization is hard to solve?

This is probably a dumb question but here it goes: Variational Quantum Algorithms (VQAs) are the leading proposal to derive quantum advantage use NISQ devices. VQAs employ classical optimization ...
user82261's user avatar
  • 181
1 vote
0 answers
78 views

I am optimising a variational quantum circuit to learn a distribution $p(x)$, but it doesn't converge over a training set $\mathcal{X}$?

I am training a variational quantum circuit to learn distributions: given data $s(\vec{\lambda})$, what is the probability distribution for the parameterisation $\vec{\lambda}$, i.e. the posterior ...
JoJo's user avatar
  • 99
1 vote
0 answers
256 views

qiskit.algorithms.optimizers callback function for all optimizers

I am aware that VQE and VQC factory supports callback functions which can allow us to store intermediate values during optimization through callbacks in its arguments. However my loss function is ...
Manas Sajjan's user avatar

1
2 3 4 5