Questions tagged [chemistry]
For questions regarding (or related to) applications of quantum information theory in chemistry or applications of chemistry in quantum computing.
70
questions
2
votes
0
answers
14
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 ...
- 31
3
votes
0
answers
37
views
Advantage of quantum computers over classical computers in fully modeling interactions between atoms?
I'm trying to better understand the advantage quantum computers offer in terms of their ability to more accurately model chemical reactions. As a way to come to a deeper understanding, my question is:
...
- 31
1
vote
0
answers
46
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 $...
- 11
4
votes
0
answers
41
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 ...
- 41
1
vote
0
answers
38
views
Subespace Search Variational Quantum Eigensolver (SSVQE) with contraints
I am trying to reproduce this paper: https://arxiv.org/pdf/2211.02302.pdf. However, I am having problems in getting the singlet first excited state (S1). The authors in the paper, they use the SSVQE ...
- 155
1
vote
1
answer
82
views
Can someone explain how Qiskit defines the electronic dipole moments?
The Qiskit API defines the electronic dipole moment as
$$
\hat{d} = \sum_{p,q} d_{pq}^x a_p^\dagger a_q ,
$$
where
$d_{pq}^x,d_{pq}^y,$ and $d_{pq}^z$ are the Cartesian components of the vector
$$
\...
0
votes
1
answer
89
views
Qiskit - Approximation of Hamiltonian energy via QPE
I'm trying to study QPE with the motivation of obtaining eigenvalues of Hamiltonian, i.e. energies of a system. My problem is, that while np.linalg.eig and VQE are agreeing on the lowest energy, ...
- 245
1
vote
0
answers
34
views
Quantum simulation for finding eigenfunctions of complicated Hamiltonians exactly
Currently I am an undergrad in chemistry taking a quantum computing class and I'm looking for a topic for a small project involving literary review of QC articles. I was wondering if quantum computing ...
- 11
0
votes
1
answer
209
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....
- 85
1
vote
1
answer
94
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” ...
- 85
2
votes
1
answer
173
views
Logical vs Physical Qubits for Quantum Chemistry DFT
How many physical qubits are required per logical qubit in a typical
Density Functional Theory implementation for a large number of atoms?
- 21
0
votes
1
answer
163
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 ...
2
votes
0
answers
76
views
Reproducing Hydrogen Molecule Hamiltonian in OpenFermion
I am learning quantum chemistry at the moment and I'm trying to understand the Hamiltonian generated by the OpenFermion package. I'm now stuck at understanding how openfermion calculates the ...
QF2QP
0
votes
1
answer
166
views
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 ...
4
votes
1
answer
134
views
If you had a 1000 qubit NISQ machine with arbitrary connectivity, what would you do?
Many current devices are constrained to nearest neighbor connectivity or small system sizes, but suppose that a NISQ machine with 99-99.5% level two-qubit gate fidelities and arbitrary connectivity ...
- 173
3
votes
1
answer
159
views
Efficiently compute $\langle 0^{\otimes n} | e^{iA} H e^{-iB} |0^{\otimes n} \rangle$ in Qiskit
From this SE question and this Qiskit tutorial, I understand how to compute the expectation such in the form of $\langle \psi|H|\psi\rangle$ or $\langle 0^{\otimes n} |e^{iA} H e^{-iA}|0^{\otimes n} \...
- 105
2
votes
2
answers
751
views
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 ...
- 155
1
vote
1
answer
155
views
Jordan-Wigner map for ionic molecule H_2^+
I want to derive the Hamiltonian of the ion molecule $H_2^+$ by making use of Jordan-Wigner map.
Thus, I used qiskit nature. I wrote down the same command given in qiskit nature. The only difference ...
- 21
1
vote
1
answer
232
views
Qiskit - nuclear repulsion energy derivative
I know a function in PSI4 computing a nuclear repulsion energy derivative located in psi4.core.Molecule.
Is there a possibility to access such function from Qiskit interface? By this "interface&...
- 245
1
vote
1
answer
82
views
Evaluating $\texttt{FermionOperator}$ equality in Openfermion
Apologies if this is the wrong place to ask this kind of question.
I have a simple question about Openfermion. I have two normal ordered FermionOperators ...
- 411
3
votes
1
answer
464
views
How to construct a parameterised UCCSD ansatz?
I want to try the UCC ansatz for problems other than quantum chemistry. For that I want to 'extract' the UCC ansatz (say from Qiskit) and supply it to my own VQE: I need a parameterised circuit where ...
- 565
4
votes
1
answer
467
views
Is molecule simulation by quantum computing critical for drug discovery?
It is often said that the molecule simulation for drug discovery will be one of the most important applications of Quantum Computing (QC).
As we all know that the entire process of new drug discovery ...
- 355
8
votes
1
answer
2k
views
Roughly speaking, How many qubits will be needed to study (or simulate) a molecule such as: C29H31N7O?
It is often said that one of the early applications for Quantum Computers will be drug discovery.
Q: Roughly speaking, How many qubits will be needed to study (or simulate) a molecule such as: $C_{29}...
- 355
2
votes
0
answers
91
views
Save output, wavefunction file and orbital information in Qiskit
I am going through LiH ground state energy calculation. I would like to know how to save the output file in Qiskit as one would do in classical computing using software like Gaussian or Psi4.
Can ...
- 31
2
votes
1
answer
806
views
How to calculate the Hartree-Fock energy in Qiskit?
I am wondering how to calculate the Hartree-Fock energy efficiently using Qiskit. For one can get the Hartree-Fock state efficiently in Qiskit, however, it seems that it is not so obvious to get the ...
- 735
5
votes
1
answer
725
views
Molecular orbitals in Qiskit
During the same minute as asking this question, I also asked this at Matter Modeling SE.
In Qiskit, each qubit corrrespond to one spin orbital. For example, the $\text{N}_2$ molecule have 10 molecular ...
- 735
2
votes
1
answer
234
views
From general Hamiltonian to Ising Hamiltonian
I would like to convert my qubit hamiltonian fom the HeH+ system that I have obtained using Qiskit to an Ising or QUBO model. I have seen multiples examples from QUBO to Qubit Hamiltonian but on the ...
- 155
1
vote
1
answer
82
views
Why the last IBMQ job of my VQE have just one circuit?
I am running a VQE over the H2 molecule on ibmq_quito and I set a callback function to save all jobs id's of all iterations. When I check the penultimate job (and the previous ones), I have 2 circuits ...
- 155
5
votes
1
answer
226
views
Is VQE or one of its variations enough to help with medicine development?
One of the reasons quantum computing is often hyped in media is because of how it'll help with vaccine and medicine development. For example, this article in Financial Express and this other in ...
- 2,865
4
votes
2
answers
297
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
6
votes
1
answer
343
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 ...
- 2,865
2
votes
1
answer
479
views
Add FreezeCoreOrbitals on ElectronicStructureProblem
I want to freeze core orbitals of my molecule and I know ElectronicStructureProblem has the possibility (es_problem = ElectronicStructureProblem(driver=driver, q_molecule_transformers=...
- 155
1
vote
1
answer
186
views
How do I work with Gaussian in Qiskit?
I am trying to run this Qiskit Nature tutorial (Vibrational Structure) and it uses the GaussianForceDriver. Every time I run the Gaussian job from Qiskit I get this message:
...
- 155
0
votes
1
answer
205
views
Getting the current variational parameters in Qiskit
I am right now using variational quantum eigensolver (VQE) to calculate the ground state of some molecules, like H2, by qiskit. The quesiton is that how to get the current parameters of the varaional ...
- 735
0
votes
0
answers
218
views
Molecular Docking using Quantum Computing
I would like to ask if somebody could suggest me a pair of ligand-Protein which had been validated and the corresponding resulting drug is already being used commercially.
I am interested in ...
2
votes
1
answer
436
views
Fermionic commutation relation using Jordan-Wigner transformation
How can one show in detailed steps that Fermionic annihilation and creation operators, under Jordan-Wigner transformation, satisfy the Fermionic commutation relations?
The Fermionic commutation ...
- 525
4
votes
3
answers
113
views
Why does joint ground state not change under action of beam splitting unitary operator?
How can one show that $\hat{U}|00\rangle=|00\rangle$ where $\hat{U}=e^{-igt(\hat{a}^\dagger_2\hat{a}_1+\hat{a}^\dagger_1\hat{a}_2)}$ and $|00\rangle$ is the unique joint zero eigenstate of the ...
- 525
8
votes
3
answers
435
views
If a Hamiltonian is quadratic in the ladder operator, why is its time evolution linear in the ladder operator?
How can one show that $\hat{U}^\dagger\hat{a}\hat{U}$ (with $\hat{U} =e^{-i\hat{H}t}$) involves only linear orders of the ladder operator, when $H$ is the general quadratic Hamiltonian $(\hat{H} = \...
- 525
4
votes
2
answers
415
views
Fermionic occupation operator and nearest neighbor Fermionic hopping interaction as a qubit operator
How to express Fermionic occupation operator $(\hat{a}_j^\dagger\hat{a}_j)$ and nearest neighbor Fermionic hopping interaction ($H_h= J\sum_{i=1}\hat{a}_i^\dagger \hat{a}_{i+1}+\hat{a}_{i+1}^\dagger \...
- 525
2
votes
2
answers
451
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
0
answers
297
views
Calculating energy function with 1&2-RDM (reduced density matrix) in Qiskit
I am now working on designing quantum error mitigation with variational quantum eigensolvers (VQE). I need to get the 1&2-RDM from Qiskit, which has already been realized by Openchemist pakages ...
- 735
1
vote
0
answers
128
views
Why measurement error mitigation does not seem to improve the result of VQE?
I try to follow this to perform measurement error mitigation for calculating H2 energy with VQE. With some modification, I did the calculation on "qasm_simulator" with the noise model built ...
- 920
5
votes
1
answer
589
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
2
votes
1
answer
312
views
No. of bits in 160 qubits computer [duplicate]
I read in a book that (https://hub.packtpub.com/quantum-expert-robert-sutor-explains-the-basics-of-quantum-computing/)
160 qubits (quantum bits) could hold $2^{160} \approx1.46\times 10^{48}$ bits ...
- 171
2
votes
1
answer
247
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 ...
- 61
1
vote
0
answers
142
views
Is there a connection between the definitions of one- and two-particle reduced density matrices?
In quantum chemistry, there are concepts about one-particle reduced density matrix (1-RDM) and similarly, the two-particle reduced density matrix (2-RDM).
Generally, for an $n$ particle wavefunction $|...
- 89
3
votes
4
answers
128
views
Where can I get circuits of interest to quantum chemistry to try and simplify?
I am a computer science undergraduate working on a project in simplifying quantum circuits (using the ZX-calculus). I was hoping to try to simplify some circuits of interest rather than randomly ...
- 705
2
votes
1
answer
421
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 ...
- 920
2
votes
1
answer
716
views
How is the Hartree accuracy calculated between the exact and VQE results?
In the Simulating Molecules using VQE section of the Qiskit textbook it states an accuracy of $0.0016$ Hartree between the exact and ...
- 401
3
votes
1
answer
254
views
What is the convention of indices for the one and two-body integrals in qiskit
I was able to calculate the one and two-body integrals for the H2 with the following code
...
- 920