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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.

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Expectation values with finite number of shots with qsimcirq

I was using qsimcirq for VQE to obtain exact expectation values of the energy for a certain Hamiltonian with ...
stopper's user avatar
  • 473
2 votes
0 answers
35 views

Portfolio Optimization with VQE (Qiskit)

I'm working on a portfolio optimization problem using Qiskit and I'm encountering an error when trying to solve a quadratic program using MinimumEigenOptimizer with SamplingVQE (V1 Primitives). Any ...
Ivan's user avatar
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1 vote
1 answer
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Portfolio Optimization with VQE

I'm working on a portfolio optimization problem using Qiskit and I'm encountering an error when trying to solve a quadratic program using MinimumEigenOptimizer with SamplingVQE. Any insights on what ...
Ivan's user avatar
  • 31
2 votes
0 answers
22 views

Variational Quantum Linear Solver

I'm studying quantum computing right now and trying to implement variational quantum linear solver to solve a system of linear equations. From what I have understood from the paper written by Carlos ...
Sangkyu Baek's user avatar
1 vote
0 answers
24 views

Do encoding schemes for variational algorithms apply to annealing methods (e.g. DWave)?

I understand there are some efficient encoding schemes for variational algorithms, that attempt to approximate the variational state using fewer qubits. I'm thinking of 2 papers in particular, which ...
IsalanOnkar's user avatar
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12 views

Using Orbital Optimization VQE

How can I use the OrbitalOptimuzationVQE class in qiskit? I want to find the ground state energy if different molecules using OOVQE but I cannot import the orbital optimization vqe class from qiskit. ...
Cheshta Joshi's user avatar
3 votes
1 answer
63 views

Complexity of Variational Quantum Eigensolvers

I am doing research surrounding VQE and am a bit confused about the complexity and its comparison to classical systems. My brief research has yielded me that classical eigenvalue solving is $O(n^3)$. ...
Jonah Sachs's user avatar
3 votes
1 answer
42 views

Prereqs for learning Variational Quantum Eigensolver (VQE)

I am trying to learn Variational Quantum Eigensolver algorithm(s) for a class. However, I am struggling because I don't understand any of the problems we are trying to solve. I want to know what I ...
researcher101's user avatar
1 vote
1 answer
98 views

Combinatorial optimization problem via VQE instead of QAOA

I'm studying about the hybrid quantum algorithms and I have a question about the VQE and QAOA. It seems like QAOA is a part of VQE that use a certain ansatz for solving combinatorial optimization ...
William's user avatar
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1 vote
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27 views

How to combine a VQE circuit with normal qiskit quantum circuit without parameters and give the measured set of qubits to the estimator?

I want to use a parameterized quantum-circuit which is $\text{CNOT}$ with another quantum-circuit that has no parameters, then after a series of gates on the second quantum-circuit, I want to measure ...
Syed Shahmir Kazmi's user avatar
2 votes
0 answers
17 views

Running VQE code using qiskit_nature on IBM computers

$\texttt{qiskit_nature}$ no longer has the $\texttt{runtime}$ feature and $\texttt{VQEClient}$ function that was used to run a VQE code on one of the IBM computers. I could not find any easy migration ...
chiral_fermion's user avatar
1 vote
1 answer
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vqe.compute_minimum_eigenvalue API of qiskit produces different eigenstate results for statevector_simulator ands qasm_simulator

I am trying to understand the usage of vqe.compute_minimum_eigenvalue API of qiskit for the statevector_simulator and qasm_simulator. I am only interested in the <...
Manu's user avatar
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1 vote
1 answer
262 views

How can I Combine Qiskit's VQE Tutorial and TSP Simulator to solve the TSP on a real backend efficiently?

I have a university project where I am trying to solve the Traveling Salesman Problem by using a real quantum backend, rather than just the VQE simulator, as in this tutorial. I found this code on ...
Aidan's user avatar
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0 answers
67 views

Usage of qiskit API MatrixOp.to_pauli_op()

I am quite confused with the MatrixOp.to_pauli_op() API. I have a hamiltonian, and it is given as input to a API MatrixOp. ...
Manu's user avatar
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2 votes
0 answers
25 views

VQE on Qiskit: getting counts per Hamiltonian term

Consider a VQE calculation (using the QASM backend and on Qiskit) that involves a qubit Hamiltonian with, say, 5 terms. Is there a way for us to get the counts for each of the Hamiltonian terms that ...
srinivasa prasannaa's user avatar
1 vote
1 answer
40 views

Reusing Parameters for Multiple Runs with Qiskit's SPSA Optimization

I am using Qiskit's SPSA optimization algorithm to find the ground state energy of various lattices (Fermi-Hubbard model) by running different circuits through it and having the algorithm modify the ...
Nidhish Sharma's user avatar
2 votes
1 answer
74 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
1 vote
1 answer
42 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
26 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
93 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
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2 votes
0 answers
26 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
45 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
178 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 ...
confusion's user avatar
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1 answer
89 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
48 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
137 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
67 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
82 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
1 vote
1 answer
219 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
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3 votes
2 answers
224 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
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1 vote
1 answer
75 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
67 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
83 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
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3 votes
0 answers
134 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
30 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
143 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
59 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
29 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
37 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
  • 473
1 vote
0 answers
102 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
36 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
74 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
4 answers
277 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
385 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
  • 181
0 votes
1 answer
54 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
112 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
445 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
236 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
  • 515
0 votes
1 answer
165 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
2 votes
1 answer
98 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

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