Questions tagged [optimization]

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

Filter by
Sorted by
Tagged with
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/...
Keane's user avatar
  • 11
0 votes
0 answers
37 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
0 votes
0 answers
9 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
0 votes
1 answer
52 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
  • 1,343
1 vote
0 answers
25 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
2 votes
1 answer
144 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
  • 21
2 votes
0 answers
68 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
40 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
78 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
57 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
55 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
46 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
60 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
54 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
102 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
30 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
49 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
78 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
2 votes
2 answers
118 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
  • 455
2 votes
0 answers
46 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
51 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
59 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
  • 2,369
5 votes
0 answers
99 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
93 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
75 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
59 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
269 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
254 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
169 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
  • 465
2 votes
1 answer
49 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
153 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
147 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
0 votes
0 answers
72 views

Can pyqubo and qiskit be used together?

I used Pyqubo to create an optimisation problem with an objective function and some constraints, but I want to use Qiskit to run QAOA/VQE on my model. Is it possible to call my Pyqubo model into ...
sohamb172's user avatar
  • 345
2 votes
1 answer
66 views

SPSA: maxiter (int) – The maximum number of iterations. Note that this is not the maximal number of function evaluations

This is from classical optimization algo. used for VQE. May I know what is the difference between maxiter and the number of function evaluation difference?
chetan waghmare's user avatar
0 votes
1 answer
142 views

scipy.optimize.minimize throwing error

I used minimize for optimizing the ansatz parameter. I wrote the line like ...
Vaishnav's user avatar
0 votes
1 answer
37 views

Find min of a quantum state L2 norm

I have a problem minimizing this norm with respect to $\alpha$: $\min_{\alpha}||e^{i\alpha}|\psi\rangle-|\phi\rangle ||^2$ (1) The result is that this achieves min when $\alpha=-\measuredangle \langle\...
Việt Nguyễn's user avatar
4 votes
0 answers
77 views

Numerical optimization over separable measurements

For a set of bipartite density operators $\{\rho_a\}_{a=1}^m \subset D(\mathcal{X} \otimes \mathcal{Y})$ each associated with a probability $p(a)$, an optimal separable measurement is a POVM $\{ \...
forky40's user avatar
  • 6,143
0 votes
0 answers
46 views

Variational Quantum Algorithms for Graph Traversal

I have a combinatorial optimization problem which on a first pass I think boils down to finding a path with a maximal score. The score for a path is computed by an auxiliary function. Are there near-...
user82261's user avatar
  • 181
1 vote
2 answers
160 views

How are the parameters in a variational circuit optimized?

I'm quite new to QML and I don't understand how the parameters in a variational circuit are optimized. I read about the parameter shift rule but what happens after the gradient is calculated ? How do ...
Duen's user avatar
  • 296
1 vote
2 answers
76 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? ...
Hamidreza Mirzaei's user avatar
0 votes
1 answer
72 views

Using BFGS for MAXCUT

In the original Qiskit QAOA implementation, the sample uses COBYLA as the classical optimizer in the following code segment: ...
Evan Camilleri's user avatar
1 vote
1 answer
106 views

GRAPE with Python?

I want to do some quick GRAPE calculations in Python. The qutip implementation is handy but I can't modify the fidelity function. However, I need to use my own fidelity function to evaluate fidelity. ...
Will Yang's user avatar
  • 177
3 votes
2 answers
206 views

How to derive quantum advantages for VQAs, if the underlying classical optimization is hard to solve?

This is probably a dumb question but here it goes: Variational Quantum Algorithms (VQAs) are the leading proposal to derive quantum advantage use NISQ devices. VQAs employ classical optimization ...
user82261's user avatar
  • 181
1 vote
0 answers
209 views

qiskit.algorithms.optimizers callback function for all optimizers

I am aware that VQE and VQC factory supports callback functions which can allow us to store intermediate values during optimization through callbacks in its arguments. However my loss function is ...
Manas Sajjan's user avatar
0 votes
1 answer
179 views

Implementation of QAOA to solve version of knapsack problem

Say I want to fill a knapsack with as many things as possible. I don't care about what they are, simply the number. But I don't want the total weight to exceed a set limit. [https://qiskit.org/...
MeltedStatementRecognizing's user avatar
0 votes
1 answer
89 views

Frequency range of superconducting qubit

What are the reasons/considerations for setting the transmon qubit frequency between around 3-6 GHz? What undesirable consequences will result if the frequency is out of the range?
Hans's user avatar
  • 75
2 votes
1 answer
63 views

Does pytket have an optimization pass that removes gate-inverse pairs & identity rotations & redundant gates and/or merges rotations?

For the following sample circuit I want to reduce the number of gates in pytket: for example, I know: Adjacent Rx gates can be merged CZ is self-inverse and cancels itself out because any Hermitian ...
mapper's user avatar
  • 35
4 votes
0 answers
37 views

How to compare Quantum Annealing and Adiabatic Quantum Computing?

I'm still unsure on the difference between adiabatic quantum computing (AQC) and quantum annealing (QA). Please critique these interpretations: AQC: Define a Hamiltonian with an easy-to-prepare ...
Ken Robbins's user avatar
1 vote
0 answers
55 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 ...
azxy132's user avatar
  • 11
3 votes
1 answer
260 views

Understanding of the transverse-field Ising model

I want to make sure whether I do understand the transverse Ising model correctly or not. The classical Ising model describes the interaction between spins in a grid and the state of spins can be ...
Kai-Chun Lin's user avatar