Questions tagged [optimization]

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

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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
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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
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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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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 $O(n^3)$. ...
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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
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1 answer
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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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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
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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: ...
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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
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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
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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
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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
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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
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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
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1 answer
134 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
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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
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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
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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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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/...
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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
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51 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
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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
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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
176 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
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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
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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
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122 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
81 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
65 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
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1 answer
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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
73 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
86 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
157 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
45 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
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0 answers
61 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
118 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
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3 votes
2 answers
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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
59 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
63 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
62 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
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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
5 votes
1 answer
109 views

Recent experimental demonstrations of variational quantum algorithms?

I am interested in the recent experimental demonstrations of variational quantum algorithms. Can someone please provide me with a list of references of recent experimental demonstrations of ...
Soumik Adhikary's user avatar
0 votes
1 answer
90 views

Portfolio optimization via quantum Zeno dynamics in Qiskit

Recently, I came across paper Portfolio Optimization via Quantum Zeno Dynamics on a Quantum Processor. In the paper, a new approach to optimization with QAOA is introduced. Instead of employing a ...
Martin Vesely's user avatar
3 votes
1 answer
67 views

How to sanity check QAOA cost Hamiltonian?

I'm trying to learn QAOA and how to apply it to a complex combinatorial problem. But for the purpose of this question I'll use the common example MaxCut. I'd like to know if I've set up my cost ...
somewhere's user avatar
3 votes
2 answers
399 views

Does QAOA require that the problem Hamiltonian be an Ising Hamiltonian as a quadratic function of the spin variables?

In the context of QAOA, I often see the problem Hamiltonian being called an "Ising Hamiltonian", and shortly after, I that the Hamiltonian is a quadratic function of the spin variables. Is ...
underdog987's user avatar
1 vote
1 answer
381 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 ...
Rogue8989's user avatar
4 votes
2 answers
218 views

Does the gradient commute with the partial trace?

Suppose I have a parameterized quantum state: $\rho(\theta) = U(\theta) \rho U^\dagger(\theta)$. I am curious to know whether the following holds: $\frac{\partial \text{Tr}_A (\rho(\theta))}{\partial \...
Jon Megan's user avatar
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2 votes
1 answer
53 views

Why is a large quantum annealer likely to leave its ground state?

For problems of significant size in quantum annealing, I have read that even for slow transitions, the annealer is likely to leave its ground state. I have not fully grasped the meaning of why exactly ...
fparisio's user avatar
0 votes
0 answers
226 views

Extracting a QUBO matrix from pyqubo

I am benchmarking different QUBO solvers for a very simple instance of the knapsack problem. Some of these solvers require the matrix, Q, and offset, b, from the equation: $$ \begin{equation} x^{\...
Waqas Parvaiz's user avatar
4 votes
1 answer
169 views

Does QAO Ansatz have any better performance guarantees than QAOA?

QAOA is a well-known heuristic for solving optimization problems, and it has the desirable property that as p -> infinity, the true minimum objective function value is reached. There is a ...
IsalanOnkar's user avatar