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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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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 ...
Ivan's user avatar
  • 11
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 ...
Maths_hawk's user avatar
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-...
Maths_hawk's user avatar
1 vote
1 answer
58 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 ...
Another Random Guy's user avatar
0 votes
0 answers
31 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 ...
Maths_hawk's user avatar
3 votes
3 answers
193 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. ...
Maths_hawk's user avatar
1 vote
0 answers
22 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 ...
IsalanOnkar's user avatar
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 ...
Maths_hawk's user avatar
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 ...
Kian's user avatar
  • 31
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 ...
Callum's user avatar
  • 1,025
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 ...
Mihir Macwan's user avatar
1 vote
0 answers
61 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. ...
Oleksii's user avatar
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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 $O(n^3)$. ...
Jonah Sachs's user avatar
1 vote
0 answers
29 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 (...
MrEightL's user avatar
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 ...
Mace's user avatar
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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. ...
Lasal Hettiarachchi's user avatar
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: ...
JiQing's user avatar
  • 35
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 ...
Aidan's user avatar
  • 61
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 \...
Silly Goose's user avatar
1 vote
1 answer
192 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 ...
yoda's user avatar
  • 11
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 ...
somewhere's user avatar
1 vote
0 answers
49 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 ...
Chuck's user avatar
  • 11
1 vote
1 answer
36 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 ...
Nidhish Sharma's user avatar
1 vote
1 answer
181 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 ...
said zhn's user avatar
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 ...
Chetan Waghela's user avatar
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 ...
HaraldRudobrody's user avatar
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 ...
Ryan Wang's user avatar
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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/...
user avatar
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 ...
ar3q5dr9's user avatar
2 votes
0 answers
58 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 ...
The Quantum Enthusiast's user avatar
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: &...
peachnuts's user avatar
  • 1,383
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 ...
Amedeo Bertuzzi's user avatar
1 vote
1 answer
203 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}...
JackAW's user avatar
  • 29
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-...
Donguk kim's user avatar
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, ...
quantum_noob_16's user avatar
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 ...
Alternative7's user avatar
1 vote
0 answers
84 views

Building a problem unitary circuit for QAOA on Qiskit

I am trying to build a circuit for QAOA that solves a Traveling Salesman's Problem, which can be represented as a complete graph with 4 nodes. After formulating the problem as a QUBO and mapping it ...
Alternative7's user avatar
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 ...
Sup's user avatar
  • 231
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 ...
Alternative7's user avatar
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 ...
user48217's user avatar
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 ...
Amedeo Bertuzzi's user avatar
4 votes
0 answers
163 views

Qiskit QAOA optimization does not work when setting simulation seed in AerSampler

I am using Qiskit's QAOA for optimization and I would like to extract the probabilities distribution obtained in the optimization loop when running the circuit with the optimal parameters set. To do ...
user26100's user avatar
1 vote
0 answers
46 views

Continuous variable portfolio optimization problem

Has anyone tried to solve the continuous variable portfolio optimization in Qiskit? I see a lot of binary variable problems but none which solve and get the optimal weights.
Jagan Natarajan's user avatar
0 votes
0 answers
66 views

How can I exactly solve a Quadratic Model with integer variables using DWave Ocean classical solvers?

As an example, let's consider the following simple QuadraticModel problem with just 3 INTEGER variables: ...
SimoneGasperini's user avatar
1 vote
1 answer
120 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 ...
17tmh's user avatar
  • 11
3 votes
2 answers
123 views

What is the algebraic result of the matrix exponential operation $e^{i A}|b\rangle$?

The circuit for the HHL algorithm looks as follows: I am uncertain what is the algebraic operation of the matrix exponential $e^{i A}$ on $|b\rangle$? If $$|b\rangle = b_0|0\rangle + b_1|1\rangle$$ ...
James's user avatar
  • 491
2 votes
0 answers
60 views

GPU Support for Qiskit's SPSA Optimization Algorithm

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 ...
Nidhish Sharma's user avatar
1 vote
1 answer
68 views

How to add a circuit layer after computing QAOA layer

I have used the Qiskit-based QAOA function to solve a combinatorial problem tsp, and I want to append a circuit after the QAOA layer, is there any way to do that? Qaoa
Affan Hussain's user avatar
4 votes
0 answers
63 views

When is a quantum algorithm considered to have a significantly superior performance over another quantum algorithm?

Suppose we have two heuristic quantum algorithms $A$ and $B$ that attempt to solve a certain class of optimization problems. Let's suppose that the benchmarking metric is Time To Solution (TTS), which ...
MonteNero's user avatar
  • 2,646
5 votes
0 answers
126 views

How to use Warm-Start QAOA in QisKit to solve non-convex QUBO problem?

I have a non-convex QUBO problem that I'd like to solve by warm-starting QAOA with a solution obtained from a continuous relaxation solution obtained by a classical algorithm. The specifics of the ...
underdog987's user avatar

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