All Questions
Tagged with vqe programming
65 questions
14
votes
3
answers
6k
views
How to calculate an Expected Value of some operator acting on qubits?
I'm trying to implement the Variational Quantum Eigensolver in Qiskit.
Suppose, I have an operator $A = \sigma_1^z\sigma_2^z$ acting on some two-qubit state $|\psi\rangle$. After a measurement I get ...
- 918
10
votes
1
answer
1k
views
Intuition behind the construction of an ansatz circuit
I'm learning about the VQE algorithm. When I looked at the declaration in Qiskit I saw you need to pass an ansatz which prepares the state. I looked at some commonly used ansatz functions, e.g. ...
- 193
10
votes
1
answer
2k
views
QUBO, Ising Hamiltonians and VQA
I understand that usually the combinatorial optimisation problems are turned into QUBO, which has a very simple mapping to Ising Hamiltonians. Ising Hamiltonians in turn have the desired properties of ...
- 289
7
votes
1
answer
5k
views
How to add several parameters in qiskit circuit?
I want to construct an ansatz circuit in Qiskit, so I need some parameters to act on the gates (e.g. RX(a), RY(b)). In the Qiskit tutorials I find a way to implement a parameter:
...
- 91
7
votes
1
answer
939
views
How can I run a VQE on one of IBMQ's Quantum Computers
I have implemented a VQE based on Qiskit's VQE function and want to run that on an actual quantum computer. My understanding was, that an IBMQ backend can be passed into the function as a Quantum ...
- 71
7
votes
0
answers
210
views
Run VQE for parametrized quantum circuit with ancilla qubits
Let's say we have the following circuit (picture and code shown below), and now the $q_0$ is an ancilla qubit. If the system of interest has only two qubits, Is there a way to use only $q_{1,2}$ as my ...
- 975
6
votes
1
answer
390
views
Use one_body_integrals to know which orbitals to freeze in ElectronicStructureProblem
In exercise 5 of the this year's IBM Quantum Challenge, you need to use the FreezeCoreTransformer (along two_qubit_reduction and ...
- 2,965
5
votes
1
answer
738
views
Simulation of a helium molecule using Qiskit
I am trying to compute the ground state energy of He-He using VQE. For this purpose I have utilized Qiskit and have written the following script:
...
- 51
4
votes
3
answers
2k
views
Creating a parameterized Operator in Qiskit
I'm trying to run a VQE for a specific custom Anzats. The Anzats is built up of an unitary matrix $U_H$, which I'm trying to created in this way:
...
4
votes
1
answer
488
views
TypeError: 'NumPyMinimumEigensolver' object is not subscriptable
I'm trying to implement the same Jupyter notebook Jin-Sung Kim gave in his YouTube video The Variational Quantum Eigensolver — Programming on Quantum Computers — Coding with Qiskit S2E4; however, I'm ...
- 173
4
votes
2
answers
344
views
How do I identify a VQE job run in real hardware?
I am running a VQEUCCFactory for H2 on a real hardware device.
...
- 155
4
votes
0
answers
232
views
Implemented QAOA returns wrong result
I try to apply QAOA algorithm to find minimal energy state of the Hamiltonian:
$H_A = \frac{1}{2}\sigma_z^1 + \frac{1}{2}\sigma_z^1\sigma_z^2$
It is expected that with p=2 my variational should ...
- 63
3
votes
1
answer
176
views
What explains my anomalously scaled up VQE?
I am trying to implement VQE from the Qiskit to obtain the ground state of a very specific Hamiltonian that has been generated via a docplex minimized quadratic ...
- 179
3
votes
2
answers
463
views
How to use VQE function in Qiskit
As part of a project I'm working on, I want to use VQE algorithm to calculate the minimal eigenvalue for given Hamiltonian. I use Qiskit on IBM UI online.
The Hamiltonian is given as a sum of tensor ...
- 193
3
votes
1
answer
380
views
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 ...
- 317
3
votes
1
answer
270
views
VQE from scratch, what have I got wrong?
I've been working on a code to run VQE with a grouped measurement. For some reason, my expectation values are slightly off from those computed by pennylane, the software I decided to use for this ...
- 690
3
votes
1
answer
2k
views
Qiskit - Simpler way to create a Hamiltonian
I am looking for an efficient way to create a Hamiltonian in Qiskit.
Following are my desired input and outputs
input: 'ZZI'
output: Z^Z^I, where Z and I are operators.
Here is how I am doing it ...
- 175
3
votes
2
answers
855
views
Qiskit best programming practices - how to speed up qiskit code?
I am currently doing some experiments using Variational Quantum Eigensolver in molecular dynamics using qiskit, and noticed that the time for execution on real backend is significantly higher than the ...
- 85
3
votes
1
answer
455
views
Variational quantum eigensolver in qiskit
I have implemented a hybrid quantum NN on a dataset to perform classification. Now I want to apply quantum PCA to my dataset to find the eigenvalues. After going through a few qiskit tutorials, I ...
- 317
3
votes
1
answer
166
views
Trouble when implement a self designed gradient in qiskit
everyone! I have trouble when implement a self-designed gradient to the VQE algorithm. The following code will pop the 'ListOp' object is not callable exception to the last line of the code when ...
- 789
3
votes
1
answer
296
views
How to find the expectation value of several circuits using Qiskit aqua operator logic?
I am using the method from this SE answer to calculate the expectation value using qiskit aqua operator logic which works well for a single circuit. Here is a simplified code snippet to demonstrate ...
- 565
3
votes
1
answer
950
views
Using Qiskit VQE for solving an eigenvalue problem
I am a new user of Qiskit and I believe there is a simple answer to my question but I have had a very hard time finding a straightforward answer. I am trying to transform a given $3 \times 3$ (...
- 41
3
votes
2
answers
609
views
How to run VQE experiments on IBMQ Backends?
The VQE.run method only takes a quantum_instance of type QuantumInstance or BaseBackend and ...
- 431
3
votes
1
answer
172
views
What is the best way to handle parametric circuits in Qiskit?
What is the best way to handle parametric circuits in Qiskit? When I create a variational form like TwoLocal and then do ...
- 878
3
votes
1
answer
382
views
VQE jobs do not appear in queue
I am trying to calculate the ground state energy of some simple molecules using 'MolecularGroundStateEnergy' tools in qiskit. When I run the calculations for very small molecules (e.g. H2, HeH+) the ...
- 57
2
votes
3
answers
1k
views
Creating a custom VariationalForm in Qiskit
I would like to use the built-in Qiskit VQE() function, with my own variational form. What is the proper way to define it? I was expecting ...
- 2,221
2
votes
3
answers
468
views
error when running VQE in Qiskit
I am running the code, which gets the ground state energy with different atomic distances of LiH. However, I encountered this error. The code is as follow
...
- 789
2
votes
1
answer
143
views
The number of qubits of the ansatz does not match the operator
I am trying to run my below code on FakeSherbrooke() system, but I am getting an error as shown below:
...
- 219
2
votes
2
answers
400
views
How to measure a qubit Hamiltonian in qiskit
I am using qiskit to get some measurement results of observables similar to the Hamiltonian. Can someone provide the way how qiskit measures the Hamiltonian (Jordan-Wigner transformed) when using VQE? ...
- 789
2
votes
1
answer
174
views
Qiskit: getting QAOA expectation
Suppose I run the Qiskit's QAOA algorithm.
qaoa = QAOA(operator=qubit_operator, p=p, optimizer=optimizer)
result = qaoa.run(quantum_instance)
There is a built-in ...
- 45
2
votes
1
answer
475
views
Increase maximum shots on IBM Hardware when running Quantum Variational Algorithms
I am interested to know whether there is a quick and elegant way of increasing the number of shots (more than 8192 shots) on IBM hardware when running variational algorithms like VQE or QAOA.
I know ...
- 14.1k
2
votes
1
answer
201
views
How to build an ExpectationBase object?
I'm trying to wrap my head around the expectation argument in Qiskit's VQE class, so to understand it I'm trying to create an ExpectationBase object to understand ...
- 878
2
votes
2
answers
535
views
Need some help with simulating molecules with VQE
I have studied the example of the simulation of LiH molecule in Learning Quantum Computation using Qiskit. It is available on this link: https://qiskit.org/textbook/ch-applications/vqe-molecules.html#...
2
votes
1
answer
324
views
How to improve accuracy of ground energy values from a VQE
Using the Qiskit textbook I have been using a VQE to find the ground state energy of Hydrogen at different interatomic distances on a quantum machine. However, the average energy value I will always ...
- 71
2
votes
1
answer
515
views
Why VQE gives an incorrect ground state energy for a chain of 4 hydrogen atoms?
I am a bit hesitant to ask this very specific question, as I feel other people need not benefit from it. But since I have struggled for a while, and I think I should get some help.
So I am using VQE ...
- 975
2
votes
1
answer
573
views
On number of parameters and operators in UCCSD in qiskit
I have two questions on UCCSD in qiskit, please see the code below.
...
- 975
2
votes
0
answers
70
views
What is the input for the interpret of Quantum Variational Regressors?
I'm trying to implement my first variational regressor using qiskit. I would like to understand how the interpret of a CircuitQNN works.
I need to define an interpret that works on the amplitudes of a ...
2
votes
0
answers
104
views
How to implement the Mixer of Quantum Alternating Operator Ansatz for Max-Independent-Set
I am trying to implement the Mixer of the Max-Independent Set from The Quantum Alternating Operator Ansatz from this paper (arXiv) in Chapter 4.2, page 15 to 17.
For every verice $v$ in the Graph this ...
- 529
2
votes
0
answers
138
views
Wrong Expectation value when implementing a VQE for the Heisenberg Hamiltonian
I tried to implement an extended Heisenberg-Hamiltonian as an extra exercise further than my homework.
My Hamiltonian is the following: $H = \sum_{NN} \sigma_x\sigma_x + \sigma_z\sigma_z$
I try to ...
- 105
1
vote
1
answer
160
views
Unable to use iSWAP in Qiskit TwoLocal entangling_block
I would like to use a general entangler in the entanglement_block of the TwoLocal function. The function seems to work with 'cz', 'cx', 'swap' gates, but it fails for 'iswap' gate. Below is the error ...
- 33
1
vote
1
answer
353
views
An effective way to submit all the jobs for VQE/QAOA at a time to an IBMQ machine?
In Qiskit, I am solving a VRP for 5 nodes and it creates 20 variables for a QUBO. It runs in a 65 qubit machines (any machine below that many fails). Now, in such a typical solvers for optimization (...
1
vote
1
answer
62
views
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 <...
- 513
1
vote
1
answer
92
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 ...
1
vote
1
answer
205
views
Recording the time taken by a VQE to find ground state energy
I want to record the time that a VQE solver takes to find the ground state. At the moment I am using:
...
- 71
1
vote
2
answers
256
views
Why is there a significant variation between the exact and VQE energy results?
When running the VQE simulation for $H_2$ over a range of distances as detailed in the Simulating Molecules using VQE section of the Qiskit Textbook, the VQE energy deviation from the exact energy ...
- 431
1
vote
1
answer
198
views
Why is circuit inverse not working for EfficientSU2?
For some reason I get the following error when attempting to find the inverse of the EfficientSU2 VQE variational form:
TypeError: 'NoneType' object is not ...
- 431
1
vote
1
answer
269
views
SPSA max_trials
I'm using SPSA as an optimizer in VQE algorithm.
The code runs on ibmq-qasm-simulator.
I've set SPSA max_trials parameter to 500, but, when I run the code, it makes ...
- 31
1
vote
1
answer
107
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 ...
- 11
1
vote
2
answers
464
views
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 ...
- 11
1
vote
1
answer
363
views
Why does the Qiskit tutorial for the Variational Quantum Linear Solver not work properly?
I am following this very nice qiskit tutorial on how to implement a simple variational quantum linear solver (VQLS). There are 3 examples implemented in the tutorial all of which are solving the $Ax=b$...
- 565