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Questions tagged [optimization]

For questions concerning how to improve quantum computers on different aspects like performance, efficiency or fault-tolerance.

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1 vote
1 answer
134 views

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 (...
1 vote
1 answer
30 views

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 ...
1 vote
1 answer
61 views

Pauli Strings on the same qubit?

I am working on solving a Max-Cut problem using fewer qubits via efficient encoding methods of more classical information onto a single qubit.Using the method of The original problem has the ...
0 votes
0 answers
7 views

"Session has been closed" Error in solving Maxcut problem by QAOA

I am trying to run this code- https://learning.quantum.ibm.com/tutorial/quantum-approximate-optimization-algorithm same way as they mentioned. After running this code, my qiskit Dashboard show 10-12 ...
1 vote
1 answer
63 views

How are edge weights "loaded" in the problem hamiltonian when solving TSP with QAOA?

I've come across several of the QAOA tutorials, and yet I'm afraid I haven't found any explanation on this. According to the Qiskit tutorial on QAOA, the cost function for the target problem has a ...
1 vote
0 answers
8 views

Solving KnapSack problem on D Wave hybrid CQM

I am solving 01 KnapSack problem for 500k items with the help of hybrid CQM solver of D Wave. And for comparison I solved same problem with CPLEX. Solution quality of CPLEX solver is better than D-...
3 votes
3 answers
196 views

How to convert a combinatorial optimization problem into a problem hamiltonian

I want to ask how I can convert any combinatorial optimization problem into a Problem Hamiltonian, since such a conversion is needed in order to solve an optimization problem on quantum hardware (e.g. ...
0 votes
0 answers
32 views

How to interpret result for an OR problem solved in Qiskit

I solved "01 KnapSack problem" in Qiskit optimization module. Though the iterations doesn't gets converged but I got an answer (may be infeasible). But my question is that how to interpret ...
2 votes
1 answer
431 views

Inequality constraint to QUBO penalty

I am trying to formulate a problem as QUBO problem and am not able to transform the inequality constraint. $$ \sum_i^N x_i \geq 1 $$ into a suitable penalty function. For N = 2, the penalty term can ...
3 votes
1 answer
49 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 $O(n^3)$. ...
4 votes
2 answers
166 views

Optimise implementation of a quantum algorithm when an input is fixed

I need to implement a quantum comparator that, given a quantum register $a$ and a real number $b$ known at generation time (i.e. when the quantum circuit is generated), set a qubit $r$ to the boolean ...
1 vote
1 answer
183 views

How to solve quadratic programming problems with continuous variables and continous constraints by using quantum algorithms?

enter image description here Here is my optimization problem I solve with classical optimization using DocPlex but I want to solve using quadratic program using Qiskit and QAOA as solver ...
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 ...
2 votes
0 answers
84 views

Solving TSP on real hardware

I'm trying to solve the traveling salesman problem using Qiskit. Following the relevant tutorial, I end up with an algorithm that uses $n^2$ qubits. This grows rapidly enough that I couldn't possibly ...
0 votes
1 answer
33 views

Solving optimization problems on real quantum hardware

I want to know how to solve a 01 Knapsack problem (or any optimization problem) on real Quantum Hardware only. I don't want to use an Application class or any classical simulation technique. If anyone ...
1 vote
0 answers
50 views

How to solve a QUBO problem by QAOA algorithm with Qiskit Optimization on a real quantum resources/hardware?

I am new to quantum computing, and I am following this tutorial trying to use Qiskit Optimization 0.6.0 to solve a simple quadratic problem by applying QAOA algorithm. As stated in the tutorial, I ...
1 vote
1 answer
106 views

How to use D-Wave decomposers?

I'm currently trying to work on a minimization problem using D-Wave hybrid and quantum machines. The problem is, shortly, an energy optimization for a network of switches and servers, linked as a ...
3 votes
0 answers
27 views

Gradient-free optimization in Qiskit without using pre-defined classes

Basically I want to build a gradient-free optimizer that classifies a very simple dataset (e.g. the sklearn make_moons) using scipy.optimize (Nelder-Mead or Powell ...
4 votes
0 answers
89 views

Where does this upper bound relating the $T$ count and $H$ count come from?

I am reading this paper on optimisation of the Hadamard gate count (Optimal Hadamard Gate count for Clifford + $T$ synthesis of Pauli rotations sequences). The idea of the paper is to optimise the ...
1 vote
1 answer
105 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 ...
1 vote
0 answers
13 views

Can dimensionality reduction be used to simplify data before using an optimization algorithm?

I am attempting to use a quantum algorithm, like a QAOA, to solve an optimization problem. I saw that qPCA can be used to simplify datasets and make them easier to analyze. Can quantum optimization be ...
1 vote
0 answers
65 views

How to convert QUBO (with non-zero diagonal elements) to Maxcut?

I want to solve QUBO with non-zero diagonal elements in matrix Q using QAOA. But I want to solve for a large enough problem size (30+ variables) and hence want to divide my circuit into subcircuits. ...
1 vote
1 answer
194 views

AttributeError: 'ADAM' object has no attribute 'optimize'

I have imported ADAM optimizer in the following way: from qiskit.algorithms.optimizers import COBYLA, ADAM, SPSA, SLSQP, POWELL, L_BFGS_B, TNC, AQGD Afterwards, I ...
1 vote
0 answers
30 views

VQLS behaves badly under simulation with noise

I was studying VQLS in https://qiskit.org/textbook/ch-paper-implementations/vqls.html and since I could not understand the circuit created by the new Hadamard test (...
1 vote
1 answer
82 views

Where is the input data X in the CV-QNN as presented in Pennylane?

I am referring to the tutorial of CV-QNN in Pennylane(Strawberry Fields). Each layer of CV-QNN can perform the operation below. Unlike other quantum neural network tutorials, where the input X and y ...
2 votes
1 answer
45 views

D-Wave hybrid solver

I am interested in using the D-Wave CQM hybrid solver for solving the job shop problem. I would like to get more information about the internal working of this solver but I have been unable to find ...
1 vote
1 answer
121 views

Solving max/min problem for graphs based on Grover

Basis is for this post ist the paper https://arxiv.org/pdf/1902.00445.pdf I want to do something similar using graph data encoded in quantum states. The circuit structure should look like this (first ...
1 vote
0 answers
40 views

How to run the post processing and return results in QAOA?

As suggested in TranspilerError: 'Number of qubits (40) in QAOA is greater than maximum (30) in the coupling_map' issue. I managed to submit the job to IBM quantum and the circuit runs successfully. ...
2 votes
1 answer
113 views

Minimizing $1 - \text{Tr}(\Phi(\rho,U)^2)$

I am looking for a computationally efficient way to minimize the following function. Let $$\Phi(\rho, U) = \text{Tr}_2(U\rho U^\dagger)$$ be a reduced density matrix where $\rho = \overline{\rho}_1 \...
2 votes
0 answers
32 views

Value error in variational quantum circuits

I am working on a project to find a unitary gate that arrives at a specific density matrix at the end. The circuit construct is shown below: ...
1 vote
2 answers
118 views

Solving a linear optimization problem with inequality constraints in qiskit? is it possible?

This is an easy optimization problem that can be classically solved. My question is that, in qiskit, how can we solve this optimization problem using IBM real machines? Is it even possible to do that? ...
2 votes
0 answers
36 views

Interpretation of rounding the output of a quantum annealing solution for optimization problems?

I understand that quantum annealing approaches output a distribution of results of 0's and 1's for thequantum state. I'm wondering if this can be interpreted in the following way: For each qubit, we ...
1 vote
1 answer
38 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
204 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}...
8 votes
1 answer
283 views

Enforcing a particular layout mapping in Qiskit

I would like to ask how to set a particular layout during transpiling. I guess that the layout can be set by the initial_layout parameter in the transpiler. However,...
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 ...
2 votes
1 answer
264 views

Quantum Annealing vs Quantum Monte Carlo: can QMC do all that QA can?

I'm working on an essay about quantum technology, and the connection between the annealing algorithm and quantum computing hardware is an important transition in the text. I'd like to know if there is ...
3 votes
0 answers
72 views

Why don't we start evolution with ground state in QAOAnsatz?

The adiabatic theorem states that we can start from an eigenstate, slowly change our Hamiltonian and still remain in the eigenstate. In the vanilla QAOA we start from $|+\rangle^n$, which is the ...
3 votes
0 answers
30 views

Why is "reducing Hamiltonian energy" also optimizing a Quantum Machine Learning model?

From what I observed, most hybrid qml architectures surround the ideas of Hamiltonian states, and it seems like our goal to optimize a circuit is to keep energy states as low as possible. But why is ...
1 vote
1 answer
76 views

What's the case when parameter-shift rule does not hold?

When the parameterized unitary is of the form $e^{-i\theta V}$, where $V$ is a Hermitian operator of the unitary, we can use parameter shift rule to calculate the gradient. In this paper, it says: &...
1 vote
0 answers
25 views

Quantum optimization and correlation function

If one imagines the nodes of the classical weighted graph as atoms, and paths between them as bonding strength, then to find the shortest path in the weighted graph, can one also look at the minima/...
0 votes
0 answers
45 views

Parallelize estimation of expectation values in Qiskit

Edit I tried using python multiprocessing library. The result with 8 cores isn't always faster than the original script that uses only one core. How can i improve the algorithm? Suppose i've a matrix ...
2 votes
0 answers
59 views

Quantum Annealing on IBMQ using Qiskit-Pulse

Qiskit-Pulse is the analog level control SDK of IBMQ hardware. Is it possible to implement an adiabatic annealing protocol/algorithm on IBMQ hardware using Qiskit-Pulse? Not asking about QAOA, which I ...
3 votes
1 answer
71 views

Python code for D-Wave Annealer

In the below screenshot, I am aware of resolving the issue by reducing num_reads as the annealing time is exceeding my allowance. Although it works, my question ...
2 votes
0 answers
97 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 ...
1 vote
0 answers
39 views

Comparing BQM and CQM solving for a tree-path problem

I'm currently working on a project for my thesis regarding BQM and CQM optimisation for a path problem. Without going too much on the details, here's some info: the structure is a tree, where all the ...
2 votes
0 answers
238 views

SLSQP optimizer(scipy.minimize) doesn't update parameters

I'm trying to find optimal parameters that minimize the cost functions. In cost function, it calculates the classical-fisher-information at a certain point(phi[0] = np.pi). Cost-function takes 3-...
11 votes
1 answer
300 views

Categories and types of quantum inspired algorithms

I have a question concerning "quantum-inspired" algorithms. There seem to be several types of algorithms that fall into this category. Some examples are: Ewin's dequantized algorithms ...
1 vote
0 answers
41 views

Running multiple amplitude estimations simulations

I am working on a mini project investigating the scalability of quantum computing in the context of option pricing. I have been following the above Finance API from Qiskit as an introduction, however, ...
1 vote
0 answers
131 views

Converting Ising Hamiltonian to a Circuit in Qiskit

I tried to solve a 2-node TSP (travelling salesman problem) by implementing QAOA on Qiskit. The graph looks like: Then I used the related Qiskit functions to convert the graph to the QUBO and map it ...

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