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Questions tagged [algorithms]

For questions about an algorithm as it relates to physics. DO NOT ask how to implement an algorithm, questions like that belong on Stack Overflow or Computational Science. DO NOT ask about the efficiency of an algorithm, or other such questions, questions like that belong on Computational Science.

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Finding ground state energy using numerical real space renormalization group

I want to find ground state energy (as well as wavefunction) for spinless $tV$ model using Real-Space Renormalization Group (RSRG) approximation. The $tV$ model is defined as $$H=H_t+H_{int}=-t\sum_{i=...
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1answer
37 views

What the difference is between Størmer Verlet and regular Verlet method?

I was wondering what the difference is between the Størmer Verlet method and the regular Verlet method, if there is any.
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0answers
274 views

Using a time-like boundary as a computer?

Question and Summary Using classical calculations and the Robin boundary condition I show that one calculate the anti-derivative of a function within time $2X$ (I can compute an integral below) $$\...
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1answer
77 views

Is photon interference really random? [closed]

I know that according to the many worlds interpretation, there is no randomness and rather there is a universal wave function that simulates an observer with a continuously branching timeline. My ...
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1answer
62 views

Could you use the Barnes-Hut algorithm iteratively— with multiple center quadrants?

I was wondering if you could use Barnes-Hut simulation beyond what it was originally intended to be. For many Barnes-Hut algorithms, the forces are only considered for a single quadrant, the centroid, ...
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0answers
119 views

Using the Kalman filter given acceleration to estimate position and velocity [closed]

I am reading data from an accelerometer. I want to use this data to estimate velocity and position. Originally, I performed a double integration of acceleration to read this data, and as confirmed by ...
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0answers
26 views

Obtaining ground state using Davidson algorithm

I want to compute the ground state of a Hamiltonian using Davidson Algorithm. I have written some code in python that I assume works alright. My problem is this: The dimension of the ground state ...
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2answers
244 views

Shor's algorithm with adversary - can (delayed) erasure of value qubits cripple calculations?

Let's look at quantum subroutine of Shor's algorithm: Hadamard gates create superposition of all (exponential number) values for input qubits. Then we perform a classical function on them, which is ...
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0answers
39 views

Have there been any patented physical models or computational algorithms? [closed]

There was a recent question (linked below) on the Law SE about the potential to patent algorithms. It appears there is a lot of gray area in the subject. Of course natural laws cannot be subject to ...
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0answers
34 views

verlet/leapfrog method lorentz force application

So I ll use leapfrog/varlet algorithm to calculate the trajectory of the particle In leapfrog method for initial values we need $v_{-1/2}$ and $x_0$. Hence I can write $v_{-1/2}=v_0-Δt/2a_0$ $v_0$ ...
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1answer
63 views

Time for Quantum Computational Prime Factorisation

I ran into this graph where the red one is $$x^3$$ and represents the number of steps as a function of factorised bits for a quantum computer. The blue graph represents the classical computer and has ...
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0answers
71 views

What is order of the Wolff Cluster algorithm?

What is the order of the Wolff Cluster update algorithm for Ising Model 2D and 3D?
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2answers
161 views

How to calculate the maximal Lyapunov exponent(s) of a multidimensional system?

I've been reading up about Lyapunov exponents for a university group project on chaos theory and I'm a little confused as to how they are calculated for a system of multiple dimensions. From what I ...
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1answer
59 views

MEMS gyro measured angular velocity vector

Notations I use: Consider a world frame $\{O_0, \vec{i}_0, \vec{j}_0, \vec{k}_0\}$ coordinate system and a rigid body $B$ with a coordinate system $\{O_1, \vec{i}_1, \vec{j}_1, \vec{k}_1\}$ attached ...
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1answer
318 views

Adiabatic QC: are there known difficult problems with spectral gap not exponentially decreasing?

Adiabatic quantum computers require slow evolution to maintain global minimum: $O(1/g^2)$ time, where $g$ is spectral gap: distance between two lowest energies. The danger is that this spectral gap ...
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0answers
145 views

Quantum Approximate Optimization Algorithm

I try to understand the 'Quantum Approximate Optimization Algorithm' (QAOA) by Farhi et al. - arXiv:1411.4028. I understand that the solution is hidden in the unitaries, but I do not understand how ...
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2answers
1k views

Shor's algorithm - why doesn't the final collapse of the auxiliary qubits cripple the computation?

Let's look at quantum subroutine of Shor's algorithm (image source): Hadamard gates create superposition of all (exponential number) values for input qubits. Then we perform a classical function ...
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0answers
51 views

Shor's algorithm Question

I have attempted to draw the circuit used to implement Shor's algorithm In this the part of till which I have understood is: 1) we Start with a n qubits in the state |0> and and also m working ...
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1answer
55 views

Markov Process in Monte Carlo simulation

I am trying to understand the detailed balance condition precisely. To get it I went on this page : https://cs.adelaide.edu.au/~paulc/teaching/montecarlo/node22.html It is written the following : ...
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1answer
50 views

What does “given one application of a black box” mean, in a quantum-computing context?

From Kaye, Laflamme and Mosca's An Introduction to Quantum Computing: Exercise 7.1.1 (Bernstein-Vazirani problem) Show how to find $\mathbf a \in Z_2^n$ given one application of a black box that ...
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0answers
149 views

Shor's algorithm - its causality and similar exploitation of QM?

Shor's algorithm is rather the most interesting quantum algorithm as it shifts a problem which is believed to need exponential classical time, to polynomial time for quantum computer, additionally ...
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6answers
13k views

Could a computer unblur the image from an out of focus microscope?

Basically I'm wondering what is the nature of an out of focus image. Is it randomized information? Could the blur be undone by some algorithm?
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0answers
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Calculating probability of precipitation based off of sensors [duplicate]

I am trying to use sensors attached to a small computer to make a very rough prediction on the probability of it precipitating. I am thinking of using a barometer to get the pressure and check for ...
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1answer
242 views

How do I use Kepler's Laws to propagate an orbit for a Two-Line Element (TLE) Set?

I need to propagate a large number of orbits (get a satellite's position at a certain time) from TLEs (two-line element sets) using Kepler's laws. Ordinarily I'd use a real propagator like SGP4/SDP4, ...
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1answer
106 views

Physical meaning behind the choice of the proposal distribution in Markov Chain Monte Carlo (MCMC) methods

Let us consider the conventions on names used in the theoretical derivation of Metropolis-Hastings Monte Carlo as outlined here, for the sake of common nomenclature. What we are building is a step-...
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3answers
168 views

High Energy Physics Algorithms in GEANT4

I have been learning to use the GEANT4 software and I came across the following statement in the Users Guide, and I couldn't help being curious as to why this was? I'm primarily a mathematician, so I ...
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3answers
238 views

Where is a classical computer better than a quantum one? [closed]

Where is a classical computer better than a quantum computer? Is there any known domain where classical algorithms always beat quantum ones, say, both in terms of time and space complexity? If yes,...
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1answer
134 views

Calculating the temperature in Creutz algorithm

Creutz algorithm is, as far as I know, a less popular Monte Carlo algorithm than the Metropolis algorithm - both are statistical mechanics algorithms. In one of his papers, Creutz shows his algorithm ...
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1answer
80 views

Assumptions in the proofs for the optimality of Grover's Search Algorithm

I was trying to understand this paper in which it is proved that Grover's search algorithm is optimal. On page 4, beginning of section 2 of the paper the author says the following In the proof I ...
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0answers
53 views

Using quantum state tomography in quantum search algorithms

Problem statement: The search space A involves elements $|0\rangle $, $|2\rangle$... $|d-1\rangle$. An oracle is provided for the function $f(x)$ where \begin{align} f(x)&=1 \quad x=x^{'}\in A \\ ...
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1answer
141 views

Test Deutsch's algorithm with constant function $f(x) = 1$

I am really, really beginner to QP. But for some reason, I am studying about Deutsch-Jozsa algorithm, and I have found this article which really helped me with understanding the pipeline of the ...
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0answers
85 views

Two dimensional plasticity with radial return

What is the proper method to scale deviatoric stresses back to the yield surface in plane stress 2D? I cannot get the radial return method to produce the desired results under plain stress conditions ...
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1answer
124 views

While solving 2D Poisson's equation, how to apply floating boundary at two edges, and Dirichlet at other two?

I have a square, at left and right edge of it; I exactly know the boundary values (Dirichlet boundary). But at top and bottom edge, I want to let the potential to float. That means I don't imply any ...
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1answer
83 views

How to simulate gravitational interaction of bodies in space?

I want to try simulating some bodies in space using the basic formulas I learned in my college mechanics class. So I know Newton's Law and some basic mechanics equations: $\vec{F} = G\frac{m_1m_2}{r^...
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1answer
306 views

Explanation of relaxation method for Laplace's equation?

Currently reading through Introduction to Electrodynamics (4th Edition) by Griffiths. I'm trying to wrap my head around Laplace's Equation, here are a couple quotes that I'd like to understand a bit ...
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0answers
78 views

Computational complexity - Quantum system [closed]

I have created a genetic algorithm to solve for the ground state of an arbitrary Hermitian matrix. it does this by working out fitness values which i have defined as -E = -$<\psi|\hat{H}|\psi>$. ...
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0answers
90 views

Quantum machine learning and exponential compression

There is a statement related to Quantum Machine Learning video lectures in which I get stuck. The explanation is derived from Seth Lloyd class. https://www.youtube.com/watch?v=Lbndu5EIWvI He starts ...
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1answer
436 views

Deutsch-Jozsa Algorithm for Non-Balanced+Non-Constant Functions?

Note: I'd imagine this will be a simple yes/no question for people better versed in this topic than myself, but nevertheless I'll provide a bit of background first for the edification of anyone who ...
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1answer
378 views

Baseline correction algorithm for Raman spectra. Raman baseline removal

Can someone please help with baseline correction algorithm? My task is to build an algorithm that normalizes baseline of spectrum WITHOUT using any additional software like Mathematica etc. I have a ...
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0answers
60 views

Matching measured eigenvalue of a matrix [closed]

Given a Matrix of the form below, we have 8 variables, $\omega_{i}$ and $J_{ij}$. we want to diagonalise the Matrix to obtain values to match the observed Eigenvalue in an Experiment. i.e. $\bar{\...
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0answers
41 views

What does the quantum behavior of indivisual in the Particle Swarm Optimization (PSO) algorithm means?

I am not specializing in physics,is it possible to explain; in simplified manner, what does the quantum behavior of individuals (particles) in the Quantum Particle Swarm Optimization (QPSO) algorithm ...
4
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1answer
83 views

Finding $\pm 2 \pi$ defects in 2-D lattice nematic simulation

I'm working on a Monte Carlo simulation of a two-dimensional nematic system (XY-like model with even-order Legendre polynomial interactions, such that the director angle $\theta$ obeys $\theta \equiv \...
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0answers
360 views

Why does the Quantum Approximate Optimization Algorithm work?

I am trying to understand the structure of the QAOA algorithm (see here) which is seen as one of the candidates to demonstrate early quantum supremacy. Yet Farhi, Goldstone and Gutmann only describe ...
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0answers
155 views

Finding the initial state in the power method for Hamiltonian diagonalization

In section III of the lecture note Chapter 1: Exact Diagonalization, Weimer has described the Power method for Hamiltonian diagonalization. The process requires the choice of an random initial state ...
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0answers
69 views

Very precise calculation of the heliocentric position coords (X, Y, Z) the point of coordinates (N/S, W/E degrees) on Earth

I need a very precise calculation of the heliocentric position coords (X, Y, Z) the point of coordinates (N/S, W/E degrees) on Earth. Currently, thanks to the algorithm which generates the position ...
3
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3answers
2k views

Quantum Grover's algorithm: constructing the black box gate

Grover's Algorithm uses a black box gate that can recognize an x such that $f(x) = 1$ for a certain function f. It inverts this x and leaves all other inputs unchanged. My question is about the ...
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0answers
138 views

Approximate cloning of a quantum state, informed by past measurements

Suppose I give you a state $|\psi\rangle$, and tell you a sequence of measurements that have been performed on it. The measurements are not guaranteed to be orthogonal to each other, or to cover the ...
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1answer
686 views

Understanding amplitude amplification in quantum computing

In short, what is the essence of amplitude amplification type of techniques that appear in quantum computing? More precisely, my main questions are, relating them more to Grover's search which ...
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1answer
138 views

Quantum computing, NP complexity [closed]

Hi I have a very limited knowledge of quantum physics and its bothering me trying to understand quantum computing. I want understand how a qubit can return usable data faster then a regular bit, how ...
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1answer
247 views

hard sphere collision condition with periodic boundary conditions

Hello Stack Exchange Physics, I am curious if there is an analytical or efficient numerical solution for the collision of hard spheres in a rectangular unit cell with periodic boundary conditions. ...