Questions tagged [noise]

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What is the link between path integral source terms and the propagator?

Consider a diffusion process defined by $$\frac{\partial \phi}{\partial t} = D \frac{\partial ^2 \phi}{\partial x^2}$$ where $\phi$ is the probability density of a particle's position and $D$ is the ...
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198 views

Rationale for definition of input/output operators in quantum langevin equations

I am going through Gardiner & Zoller's 'Quantum Noise', and following the derivation of the Langevin equations in terms of input/output operators. Let the bath Hamiltonian be: $$H_B=\hbar\int_{-\...
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47 views

Pink noise and averaging

Disclaimer: I am aware this is somehow at the boundary between physics and statistics, but I have the impression that it is more likely that somebody doing/studying physics, rather than statistics, ...
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2answers
346 views

The origin of contact noise?

I was trying to measure the noise of a device with metal probes. I was not sure whether I should trust the results because I was told contact noise might contribute to some degree. I am a little ...
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54 views

Why do I hear static when I plug in my earphones incorrectly?

I use simple earphones which are wired with my laptop. Most of the times I unconsciously plug them in without looking and at times instead of going in the port they touch the laptop body near the port ...
3
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60 views

Johnson Nyquist noise with voltage driving

In his 1928 paper, Nyquist derives the famous Johnson-Nyquist noise relation which is, to be very precise according to his paper: It gives the variance of the voltage at the boundary of a resistor ...
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78 views

Transition rate in systems without thermal noise

I've been lately reading about Transition State Theory (TST) and different methods to estimate the transition rates between metastable states in the context of chemical reactions using the review ...
3
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0answers
42 views

Why does shot noise becomes 'non-shot' beyond a certain threshold?

My understanding of shot noise is that if a process is Poissonian, the noise observed is 'shot noise' and its total variance will go hand in hand with the mean value of the noise. But, judging from ...
3
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56 views

Why do I hear noise out of my headphones when rubbing its male connector to a metal container's wall filled with water?

When I rub the male jack of my heaphone cable to the inner walls of any metal container filled with water, I can hear crackling noises. I don't know how could this little bit of rubbing generate such ...
3
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299 views

Transition rate of two level system subjected to noise

(this question is simpler than its length implies. I did this on purpose to provide a nice complete development for future readers) The setup Suppose we have a two-level quantum system with ...
3
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1answer
595 views

Johnson-Nyquist noise for resistive element with temperature gradient

In Nyquist's 1928 paper, Thermal agitation of electric charge in conductors, the voltage noise for a resistor is derived assuming a circuit in thermal equilibrium and one temperature. How does the ...
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14 views

Derivation for resistor noise using transmission lines

Typically, in the derivation used for resistor noise, I see a hypothetical voltage source (the equivalent noise source) with a source resistance of R, connected to a transmission line of ...
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37 views

What is all the known information contained in thermal noise?

I've read up a little bit on thermal noise, which is an unavoidable noise in materials when $T>0K$. Thanks to this noise, by measuring the voltage across a material, it is possible to extract the ...
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53 views

How to calculate precision of Pound-Drever-Hall technique?

When I read the fifth section (Noise and fundamental limits: how well can you do?) of Eric's article, I have question. In this section(page 85 and 86), Eric discussed the shot noise, and gave the ...
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80 views

Noisy limit of sinusoidal modulation of the frequency of a two level system

I've been reading the paper Motional Averaging in a Superconducting Qubit by Li et al. from 2011, in which they study what happens when they modulate the frequency of a two level system. Specifically, ...
2
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0answers
48 views

Is LIGO designed as a bandpass instrument?

This question intended for those that may have personally worked on LIGO and are knowledgeable about its detailed systems architecture. I understand that LIGO basically uses a Michelson-Morley type ...
2
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1answer
351 views

Definition of contrast-to-noise ratio?

I have been looking at definitions of the contrast-to-noise ratio. As indicated in numerous sources (e.g. here (page 12)), the contrast to noise ratio between two signals $A$ and $B$ is: $$ CNR=\frac{...
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1answer
48 views

Coupling constant for an object in a photon gas

I want to model a photon gas as a bath of harmonic oscillators, and examine the effects of this bath on a system which is also a harmonic oscillator. The trouble I'm having is in relating the ...
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227 views

LIGO detection statistic, SNR formula

According to B. P. Abbott paper published in Physical Review Letters, "Observation of Gravitational Waves from a Binary Black Hole Merger" http://journals.aps.org/prl/abstract/10.1103/PhysRevLett....
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365 views

Schottky and shot noise

I am looking for a little history on shot noise: when was it first predicted and first measured? In particular, what was the role of Schottky? His 1918 paper "Über spontane Stromschwankungen in ...
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2answers
139 views

Why does image noise happen?

Why are digital images shot with a high iso (which means the camera sensor is much more sensitive to light) so much grainer than pictures taken with a lower iso? Here is an example of the type of ...
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0answers
17 views

Normalization of Phase Noise / RF Power Spectrum to 1 Hz RBW

I used a Rohde & Schwarz Phase Noise Analyzer to take some phase noise and RF spectrum measurements. All in all, I'm trying to compute the linewidth of a laser from a measurement. I cannot detail ...
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15 views

Does laser coherence length impact phase noise?

I am trying to simulate laser phase noise numerically by creating a random phase $\phi(t) = \sqrt{2\pi\Delta\nu_L} \int_{0}^{t} dW(t)$, where $\Delta\nu_L$ is the laser linewidth in Hz and $\int_{0}^{...
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35 views

Decoupling noises

This is an experimental physics problem: Say I have 3 random variables $P_1, P_2, P_3 $ such as : $\Delta P_i=\Delta_Q P_i +\Delta_0P_i \ \ \forall i$, where $\Delta$ is the variance, this equations ...
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1answer
37 views

Nyquist noise and thermal equilibration

Let there be given two identical lumped element resistors $R_1=R_2$ whose heat capacities are also equal and given $C_1=C_2$. We assume the resistors are attached to thermostats, one at temperature $...
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1answer
146 views

Spectral density of fluctuations (white noise/delta-correlated process)

Let I be the current flowing across some junction as a result of N charge carriers of charge q. And let $\langle I (t) \rangle$ be its average. Assume a particle number distribution such that its ...
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26 views

LISA acceleration noise formula

In the Laser Interferometer Space Antenna (LISA) mission proposal document, section 4.2 (page 17) there is a formula for the test mass acceleration noise level: \begin{equation} S_a^{1/2}\leq 3\cdot ...
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50 views

Noise power spectral density and $|X(\omega)|^2$. Why are those quantities associated usually ? Their definitions are different

I consider a generic signal $X(t)$. We could imagine to fix ideas $X(t)=\sqrt{R}I(t)$ ($R$ being a resistor and $I$ current flowing through it) The energy of this signal is defined as $E=\int_{-\infty}...
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94 views

What part of static noise in FM radio and analog TV is due to CMB?

When you switch analog FM radio or analog TV channel to non-existing station (in-between channels),- then you hear/watch just plain static noise. Question what I am interested is- what part exactly of ...
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18 views

Is there a graphical summary of which modulation technique to use in communication systems using Visible Light Communication techniques?

I am currently looking at various papers written (some listed at the bottom) that discuss how laser pulses can be modulated to send encoded messages to a receiver for communication systems. The more I ...
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1answer
26 views

the mechanism of sound generation of plunging jet

can anybody give me an explanation about what is the acoustic source for a plunging jet, like tap flow enter into a basin? is there any exiting theory like Lighthill theory in aero-acoustic to explain ...
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0answers
51 views

Is thermal (Johnson) noise intrinsically stochastic?

Thermal (Johnson) noise is caused by electron collitions. Since movement of electrons is intrinsically stochastic according to Quantum Mechanics (assuming the Copenaghen interpretation), does this ...
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23 views

Is there a physical limit to silent quadcopters, and what are the parameters?

Quadcopters can now navigate fairly well indoors. One could imagine many possible uses, including telepresence and security, but which are limited because of the loud noise. Assuming zero 'motor ...
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1answer
79 views

Noise covariance matrix

I've been trying to understand this paper. The paper seems to be about analyzing noise properties of a superconducting coplanar waveguide microwave resonator. They use an IQ mixer to perform ...
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2answers
337 views

Converting from free field to reverberant field (Noise break out to outside)

If you have a noisy room (reverberant field) and you want to know how loud it sounds to a guy standing in the park outside how do you calculate that. I have a formula in a book about noise break-out ...
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0answers
88 views

Is there a simple uncertainty-principle explanation for the quantum noise limit of an amplifier?

The quantum noise limit of a microwave amplifier's effective noise temperature, $T_N$, is found by setting $k_B T_N=hf/2$, where $f$ is the frequency of the detected radiation. This may be off by a ...
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1answer
260 views

Noise add to the Lindblad equation or Liouville-Von Neumann equation

I am working on an open system and I would like to use the Lindblad master equation but also I would like to add noise to it. If is possible. All the books and papers I did read about tells me that ...
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0answers
55 views

Can quantum error correcting codes compensate for post-selected quantum teleportation?

The process for quantum teleportation ends with two fixup operations, applied by Bob, conditional on the respective results of two measurements done by Alice. Sometimes, when you read about ...
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0answers
186 views

Gaining intuition over Hamiltonian for qubit systems

A typical Hamiltonian for a two state system with some driving field can be written as $$H=J(t)\sigma_z+h\sigma_x$$ This represents a qubit system driven along a single axis. On the other hand we ...
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196 views

Noise created due to change in Air Pressure

Background : My blower in one of the experiments is generating noise due the a short airflow path to atmosphere. The reason is due to a sudden change in pressure (high to low) the high noise is ...
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47 views

Relating noise spectral densities of magnetic flux and voltage

My problem is as follows. I generate a voltage $V$. This voltage is applied to a resistor R, producing a current $I$. This current is then passed through a superconducting coil, producing a magnetic ...
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0answers
233 views

Finding the dependence of dephasing time on flux noise in Transmon Qubits

Before introducing some relevant concepts I'll begin by stating my question. What I am looking for is the connection between the noise the flux through the SQUID in my transmon qubit (related to the ...
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0answers
105 views

Noise of a fiber optic gyro

I have not much experience with noise handling or calculations, furthermore in my researches couldn't find a similar problem, so here is my attempt: Having a fiber optic gyro that is rated with a ...
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0answers
1k views

Thermal noise from capacitor; circuit analysis

I'm trying to model the thermal noise from a capacitor. The capacitor is connected directly into an amplifier with resistance $R_{A}$ and capacitance $C_{A}$. A noisy capacitor is modelled as a ...
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1answer
35 views

Vibrational noise for scientific apparatus on a satellite

Say we're running an experiment on a satellite in some earth orbit. For example, maybe we're imaging something with transmission electron microscope or we're catching atoms in ion traps --- really ...
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13 views

How to experimentally verify, if the intensity of light from an External Cavity Diode Laser (ECDL) is shot noise limited?

I have an ECDL and i want to experimentally verify if it is shot noise limited or not. Any reference will be helpful.
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10 views

Compute the variance of spectroscopic Shot Noise in cosmology context

I would like to know the right expression for the expression of variance of Shot noise in spectroscopic probe. Sometimes, I saw $$\sigma_{SN,sp}^{2} = 1/n_{sp}$$ with $n_{sp}$ the average density of ...
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20 views

Relationship between noise spectral density and quantum absorption/emission: I don't understand the derivation

In this paper, on page 57 he performs a calculation that I don't understand. Maybe there is an implicit physical assumption behind so this is why I am asking it here. The context (not necessary to ...
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0answers
9 views

Expression for covariance matrix as a function of distance

I am studying a tracking problem in which the measurement noise, assumed to be Gaussian, increases as a function of the distance to the target. I am seeking an expression for the covariance of this ...
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0answers
20 views

Data augmentation in $k$-Space

I am working on denoising data in $k$-space for MRI (magnetic reasonance imaging) using Convolutional neural networks, and I am wondering what would be some suitable data augmentation techniques ...