Questions tagged [optimization]
For questions concerning how to improve quantum computers on different aspects like performance, efficiency or fault-tolerance.
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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 ...
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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 ...
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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: &...
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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 ...
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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}...
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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-...
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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, ...
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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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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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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:
...
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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 ...
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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$$ ...
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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 ...
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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
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 $$ into a suitable penalty function. For N = 2, the penalty term can ...
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Does the gradient commute with the partial trace?
Suppose I have a parameterized quantum state: $\rho(\theta) = U(\theta) \rho U^\dagger(\theta)$. I am curious to know whether the following holds:
$\frac{\partial \text{Tr}_A (\rho(\theta))}{\partial \...
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Why is a large quantum annealer likely to leave its ground state?
For problems of significant size in quantum annealing, I have read that even for slow transitions, the annealer is likely to leave its ground state. I have not fully grasped the meaning of why exactly ...
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Extracting a QUBO matrix from pyqubo
I am benchmarking different QUBO solvers for a very simple instance of the knapsack problem.
Some of these solvers require the matrix, Q, and offset, b, from the equation:
$$
\begin{equation}
x^{\...
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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 ...
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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 ...
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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?
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scipy.optimize.minimize throwing error
I used minimize for optimizing the ansatz parameter. I wrote the line like
...
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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\...
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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 $\{ \...
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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-...
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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 ...
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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?
...
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Using BFGS for MAXCUT
In the original Qiskit QAOA implementation, the sample uses COBYLA as the classical optimizer in the following code segment:
...
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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. ...
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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 ...
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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 ...
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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/...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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