Questions tagged [chemistry]
For questions regarding (or related to) applications of quantum information theory in chemistry or applications of chemistry in quantum computing.
66
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Number of Qubits Required for Simulation of Caffeine and Penicillin Molecules
I recently read this report from BCG, which stated:
For scientists trying to design a compound that will attach itself to,
and modify, a target disease pathway, the critical first step is to
...
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Quantum Chemistry and Quantum Computing
Predicting the energy of molecules to high accuracy during the course of a chemical reaction, which in turn allows us to predict reaction rates, equilibrium geometries, transition states among others ...
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Impact of ordering Hamiltonian terms for Trotterization
In Trotterization, the typical Hamiltonian considered is:
$$ H = \sum_{p, q} h_{pq} a^{\dagger}_p a_q + \sum_{p, q, r, s} a^{\dagger}_p a^{\dagger}_q a_r a_s $$
Which is then converted into a sequence ...
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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} = \...
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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}...
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Quantum chemistry: references
I have heard about Quantum chemistry as one of the main applications of quantum computers. However, I have not found concrete related articles with circuit-implementations for these applications.
...
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What are some current applications of Quantum Computing in drug discovery? Are there any test examples of this?
I am interested in applying the power of Quantum Computing to drug discovery. Although I realize that quantum computing is limited in regards to modeling drug-like compounds and their interactions ...
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Developing quantum circuits for specific quantum chemistry configurations
I am interested in learning more about the following: would it be possible for me to simulate a molecule consisting of copper ions through a quantum circuit?
And if so, can that circuit allow me to ...
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1
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Defining qubit operator from scratch
I'm a beginner with Qiskit and the Python language at all.
Here is my question:
One of the VQE function arguments is qubit operator (qubitOp).
I saw some examples ...
6
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1
answer
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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 ...
- 2,695
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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 ...
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Do we know anything about the computational complexity of the exchange-correlation functional?
Density functional theory is based on the Hohenberg-Kohn (HK) theorems and aims to compute the ground-state many-body wavefunction of a physical material and/or molecules.
To put it simply, the HK ...
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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 ...
- 2,695
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What set of quantum logical operations can one use to benchmark spin Hamiltonians?
Chemistry background: In magnetic molecules, it is sometimes the case that one can adjust the time-independent Hamiltonian by chemical design. This means there is freedom to adjust parameters in the ...
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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 ...
- 515
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2
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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 \...
- 515
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Electronic structure calculations and the Ising model: practical?
I was reading this paper which introduces a mapping from a qubit Hamiltonian to an Ising model. Firstly, the first step of the mapping seems to assume that we know an eigenstate of the system (correct ...
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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 ...
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1
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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 ...
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How do I identify a VQE job run in real hardware?
I am running a VQEUCCFactory for H2 on a real hardware device.
...
- 143
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1
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480
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Simulation of a helium molecule using Qskit
I am trying to compute the ground state energy of He-He using VQE. For this purpose I have utilized Qskit and have written the following script:
...
- 41
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votes
1
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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} \...
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Primer for learning about quantum circuits simulating systems
I am interested in a couple of books or arXiv links to learn how to develop quantum circuits for the purpose of simulating quantum multi-body systems. Moreover, I am interested in learning how to ...
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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 ...
- 555
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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 ...
- 625
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Rabi oscillations with different energy differences
Please check this Rabi oscillations image1:
Now, let's say I want to create a superposition of E1 and E2, so I started an EM field tuned to a frequency related to E2-E1. But, let's say there is ...
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207
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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
...
- 890
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1
answer
302
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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 ...
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How to apply unitary coupled cluster to a spin problem?
I understand how to apply UCC to a problem formulated in a second-quantized (fermion) form: you start with some state and then create a unitary operator out of single-body (or double-, triple- and so ...
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Can one make NV centred type qubits from analogus materials in the periodic table?
Can one replace Nitrogen with Phosphorus and Carbon with Silicon and so on?
What would be the conditions that would preclude such a realisation? Are there any implemenations so far?
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Spin precession using a laser
According to Christopher Monroe: "Modular Ion Trap Quantum Networks: Going Big", the hyperfine states of the valence electron in the Yb+ is used as a qubit. I know that we can change the spin ...
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2
votes
2
answers
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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 ...
- 143
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1
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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 ...
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1
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561
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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 ...
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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
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1
answer
636
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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 ...
- 675
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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 ...
- 143
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1
answer
309
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Fermionic commutation relation using Jordan-Wigner transformation
How to show in detailed steps that Fermionic annihilation and creation operators under Jordan-Wigner transformation satisfy the Fermionic commutation relation
$\{\hat{a}_i,\hat{a}_j\}= \{\hat{a}_i^\...
- 515
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1
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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=...
- 143
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2
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367
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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
187
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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 ...
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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 ...
- 890
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1
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248
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Modifying Qiskit Hamiltonian
I'm fairly new to the Qiskit API. I was wondering if I could get some assistance with trying to implement our technique of projecting out a new Hamiltonian from the ground-state Hamiltonian. The ...
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1
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What are the rules that map the second-quantized fermionic Hamiltonian into spin-form in OpenFermion?
We can use OpenFermion to get the molecular Hamiltonian in the form of:
$$H = \sum_{pq} h_{pq} a_p^\dagger a_q + \frac12 \sum_{pqrs} h_{pqrs} a_p^\dagger a_q^\dagger a_r a_s$$
and we can also use the ...
- 79
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0
answers
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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
2
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0
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71
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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.
Also, ...
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217
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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 ...
- 675
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0
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Hamiltonian of the valence electron of Yb+ ion [closed]
Let's say I have chosen the valence electron of Yb+ as my qubit. I want to consider it's hyperfine structure as the two-level energy states.
Are my following assumptions correct?
If the magnetic ...
- 583
1
vote
1
answer
135
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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 ...
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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
$$
\...
