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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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:
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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?
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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 (...
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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 ...
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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 ...
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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 ...
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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....
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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:
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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” ...
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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 ...
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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 ...
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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.
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Variational Quantum Algorithms and Quantum Advantage
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 ...
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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 ...
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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 ...
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getting error while simulating LiH using VQE
I wrote code again using updated qiskit nature libraries but I am facing error , I need help to finding solution so that we can run this code on latest version of qiskit.
I am attaching code below........
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Qiskit VQE output
When running Qiskit vqe.compute_minumum_eigenvalue() a dictionary of various values are returned.
Within this dictionary are two parameters called ...
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Evaluate a gradient with a specific backend (Qiskit)
I'm following the tutorial on gradients in Qiskit. Suppose I have the following:
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How VQE is scalable if the dimension of the Pauli basis of the given Hamiltonian grows exponentially with the number of qubits?
For a given Hamiltonian operator $H$, It's possible to approximate its smallest eigenvalue using VQE. Any Hamiltonian is a Hermitian operator. Therefore, for a system with $n$ qubits, the set $S$ of ...
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gradient estimations on variational quantum algorithms
Other than the two famous parameter-shift rule and finite difference method, is there any other (perhaps simple) methods to estimate gradients of a cost function in variational quantum algorithms?
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How to upload a program in Qiskit runtime
I'm trying to use qiskit runtime to run my own version of VQE (the idea is to later run other algorithms). I understand that to use the ...
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Adding controllable noise to VQE to find ground state energy
I am wanting to add noise to my code which uses VQE to find ground state energy for LiH at various inter atomic distances. The code I am wanting to add to is the code found from the qiskit text book. ...
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unexpected keyword argument in qiskit vqe
I want to find the estimate of the ground state energy of my Hamiltonian H that is implemented as PauliSumOp in my variable <...
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How does the Active Space Transform work theoretically?
I have a question about the ActiveSpaceTransformer which is used in vqe calculations for a molecule of LiH in Qiskit. In the documentation the inactive Fock operator is defined.I don't understand why ...
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Calculating state fidelity and space complexity of Minimum Eigen Optimizers (VQE, QAOA and Grover Optimizer) in qiskit
I'm a beginner in using Qiskit and my Computer Science background is not extensive. But I understand the Quantum Physics aspects of it relatively well.
I solved a QUBO problem in Qiskit using VQE (...
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qiskit-nature accessing circuit
There are some very nice examples on how to handle circuits using qiskit.
However, once we get to the qiskit-nature documentation, it feels like a complete new world for the untrained eye.
I am ...
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Best tutorial about the variational quantum eigensolver (VQE)
I want to find a tutorial on VQE with a good valance between the theoretical background of the method, and it's working implementation on QPU. Covering advanced topics such as quantum error ...
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How do you add spin up and spin down fermions to a FermiHubbardModel class in Qiskit?
I've been programming a FermiHubbardModel class with the Qiskit library for a VQE, but the class only shows input options for the U (onsite) and t (hopping) parameters when I construct a LineLattice.
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Qiskit: evaluating expectation value of S^2 operator
I am trying to obtain the expectation value of the S^2 operator with respect to VQE wave function in an older version of qiskit (0.26). To that end, I tried:
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Why is HF Initial point seems to be better than MP2 initial point in qiskit?
I am trying to design a custom VQE algorithm using qiskit. The main customization of the algorithm is in the minimization of expectation value of the Hamiltonian. To accomplish this, I have used the ...
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Difference between using CircuitSampler vs Execute methods on obtaining expectation value
For a hybrid, VQE-type optimization in qiskit, in order to compute the expectation value of a Hamiltonian, we can use CircuitSampler on some Pauli sum operators, as well as Execute method on a list of ...
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Interpreting VQE and QAOA based solutions in portfolio optimization
I am going through portfolio optimization using Qiskit. It really looks interesting. The module has both VQE and QAOA algorithms for optimizing the portfolios.
In the VQE based solution the ...
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SPSA optimizer picking up previous iterations evaluations
I would like to write a modified SPSA which takes up an optimization history of a previous VQE simulation. Is it something that can be done? The purpose of this is to cut down the amount of time and ...
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Clarification on the usage of class UCC of qiskit_nature
I am trying to develop a customized VQE algorithm in which I am making use of the class UCC of qiskit_nature. I am having trouble understanding the outputs of the methods of the class. I have ...
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How to send another job to a device before finishing the last job?
Is there any way to create a for loop that would send a few jobs to run on a quantum computer simultaneously? I tried:
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References for two-local forms in QISKIT
I am using 'Two local' form of QISKIT as a waveform ansatz in VQE to compute ground state. QISKIT documentation does not provide references to all the entangling options. Is there any other place ...
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Help on PySCF library
I am a student and I am trying to use qiskit nature in order to calculate the ground state energy of a molecule. My probelm is that when I try to run the simulation an error message comes out:
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Why does Parity mapping allow 2 qubit reduction?
when mapping from fermionic to qubit hamiltonian, using Parity mapper allow us to reduce 2 qubit in the final hamiltonian. I would like to understand which kind of symmetries are being used and how it ...
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For the same operator, when I use qiskit's VQE and QAOA solutions, the results are completely different
Specifically, I can't get the correct result using QAOA，A total of 6 qubits were used in this work，this is part of my code using VQE and QAOA
localsim = BasicAer.get_backend('qasm_simulator')
...
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Barren Plateau as a consequence of 2-design?
Initializing a parameterized quantum circuit with a unitary sampled from a uniform distribution (so sampling from the Haar distribution) or in a weaker form: a unitary which is a unitary 2-design, ...
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Expected Minimum Clique Coverage?
I'm curious if there is literature on this and, if there is, where to find it. Here I'm using ``clique" to mean a set of observables which all commute with each other. I also include the identity ...
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Performance metrics in QSVM
I have implemented QSVM on breast cancer dataset using link: "https://qiskit.org/documentation/stable/0.24/tutorials/machine_learning/01_qsvm_classification.html" but unable to compute other ...
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Expectation value of Pauli string for VQE
One approach to get the expectation value $\langle\psi|P\psi\rangle$ of a pauli string $P\in \{I, X, Y, X\}^{\otimes n}$ is the following.
Let $(a_i, |\lambda_i\rangle)$ be eigenvalue-eigenvector ...
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How is this Variational Quantum Singular Value Decomposition paper efficient in any way?
Link to paper here.
This algorithm seems neat but the unitary decomposition of the matrix M generally takes an exponential number of Pauli basis elements in the number of qubits $N$, therefore an ...
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What is the original paper introducing the Variational Quantum Eigensolver?
My question is very simple. I am looking for original paper where Variational Quantum Eigensolver (VQE) has been introduced. After some Googling I was able to find many applications of VQE and its ...
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Expectation value of Pauli strings for VQE
I am studying VQE and have boiled it down to a matter of determining the expectation value of Pauli strings:
$$\langle H \rangle = \sum_i \alpha_i \langle\psi|\hat{P_i}|\psi\rangle.$$
I have been ...
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Hamiltonian & QubitMappingType cannot be imported from qiskit.chemistry.core
I'm trying to implement the same Jupyter notebook in The Variational Quantum Eigensolver — Programming on Quantum Computers — Coding with Qiskit S2E4;however,I found a problem:
Error:
...
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Convexity of cost function in quantum machine learning
I have a small confusion on convexity of the most typical cost function considered in many qml papers: $\text{Tr}(\rho O)$, where $O$ is a Hermitian operator and $\rho$ is a quantum state. This is ...
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Qiskit: QAOAnsatz circuit with custom Hamiltonian
I am trying to implement the Quantum Approximate Optimization Ansatz by creating a parametrized subcircuit
$$V (α) = e^{−iH_M α_1} e^{−iH_D b_1} ... e^{−iH_M α_n} e^{−iH_D b_n}$$
with the custom ...
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Why does VQE with pennylane and scikit-optimize gp_minimize give 'func must be scalar' error?
I am trying to replace the SPSA optimizer in the VQE tutorial of pennylane by the bayesian optimizer of scikit-opimize.
When running the code below I get the error "func should return a scalar&...
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