Questions tagged [optimization]
For questions concerning how to improve quantum computers on different aspects like performance, efficiency or fault-tolerance.
215
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How to map a constraint to the output of a binarized continuous Quadratic Optimization problem?
I have the following quadratic cost function
$$
J(t) = \int_{0}^{t} \left[ z(\tau)^\ast A z(\tau) + w(\tau)^\ast B w(\tau) \right] d(\tau)
$$
where $w = -Rz$ and A and B are matrices whose values are ...
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Maximisations over LOCC measurement protocols
I have a quantity that I want to calculate by maximising over LOCC measurement protocols. How does one even approach this problem, both analytically or numerically? Has any work been done on the same? ...
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Does optimization via Hamiltonian evolution have an analogy like gradient descent?
I'm trying to find out, if there is a simplified concept to understand what is occuring during quantum annealing/ Falqon/ Hamiltonian evolution like algorithms.
During classical gradient descent ...
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Transpilation error: CircuitError: 'The amount of qubit(0)/clbit(0) arguments does not match the gate expectation (2).'
I am trying to implement a algoritm that reduces the number of qubits required for MAXCUT optimization. I need to create a custom gate that encodes a diagonal unitary matrix where the diagonal ...
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How to calculate guessing probability for quantum key distribution?
There are 3 Projections $P_1$, $P_2$, and $P_3$ corresponding to 3 inputs $x = 1, 2, 3$ for Alice. Similarly, the same projections are used by Bob for $y = 1, 2, 3$. Each input has 2 outcomes, $a = 1, ...
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Is there any mathematical technique to find the exact solution of a QUBO problem?
Suppose I am given a QUBO problem consisting in the minimization of a quadratic function $\vec{x}^T Q \vec{x}$ over a binary-valued vector $\vec{x} \in \{0, 1\}^n$, with $Q$ a symmetric indefinite ...
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Converting a Quartic Term into Quadratic Form in QUBO for Prime Factorization
This is a continuation of this question and I encourage you to read that as well.
I'm trying to embed the prime factorization problem into the form of a QUBO. To do so, let $p$ and $q$ be two real ...
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How to easily get the number of qubits required when using QAOA from qiskit_algrithms?
I would like to know if there is a easy way or native solution to retrieve the number of qubits that is required when using QAOA from qiskit_algorithms package to ...
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Optimization in QAOA should only return global minimum?
I am working on a project dealing with QAOA and I have some theoretical question about this last one. I hope I could find someone familiar with the field.
QAOA is usually used to solve combinatorial ...
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Is purity convex in time?
Is the purity $\mathrm{Tr}[\rho(t)^2]$ of a quantum state $\rho(t)$ that evolves according to a time-independent Lindbladian $\partial_t \rho = \mathcal{L}[\rho]$ convex in time $t$?
I suspect the the ...
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Portfolio Optimization with VQE (Qiskit)
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 (V1 Primitives). Any ...
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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 ...
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"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 ...
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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-...
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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 ...
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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 ...
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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. ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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. ...
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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 (...
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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 ...
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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.
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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 ...
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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 \...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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1
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280
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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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