Questions tagged [decoherence]
Quantum decoherence is the *irreversible loss of ordering of the phase angles* between the components of a system in a quantum superposition resulting in classical or probabilistically additive behavior, thereby suppressing interference of wavefunction components.
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Can there be decoherence of quantum fluctuations in Minkowski spacetime?
I was reading a paper (https://arxiv.org/abs/1008.0808) on whether observers (like Boltzmann Brains) arising from vacuum fluctuations could occur in a Minkowski vacuum. I had a a question on this:
The ...
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Are the wave-functions in surrounding objects collapsed?
Can we say that the wave functions in a cup of tea, a blanket, a stool, and other surrounding objects, are collapsed due to the constant interaction of these objects with photons and other radiation?
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How can the Lindblad master equation model decoherence?
In some references that I have read, a crucial assumption in deriving the Lindblad master equation is that the system and environment remain separable for all time. Hence, the system and environment ...
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Importance of Environment in System-Observer Entanglement and Decoherence
It has been stated in places such as Sean Carroll's talks that including the environment in our description of a quantum measurement process is important in understanding why we do not "feel like&...
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Why are measurements considered irreversible?
In quantum mechanics, every interaction is described by a unitary Hamiltonian operator. We expect that a measurement is no different from any other interaction, yet in the standard way of treating QM ...
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Loss of coherence in the double-slit experiment
Let's suppose we perform the double-slit experiment, using two detectors to detect which slit the particle has passed through. I describe the detectors using quantum mechanics, so they are represented ...
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Are temporal coherence (for classical EM waves) and quantum coherence related concepts?
For my wave optics class, I was taught that the temporal coherence of a light source is the average time interval for which the phase of that light is predictable, after which the source will undergo ...
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Why is a monochromatic wave temporally coherent for all time delays $\tau$?
I've been learning about coherence of waves and the Wikipedia page on says a monochromatic electromagnetic plane wave is coherent because:
A wave containing only a single frequency (monochromatic) is ...
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Did "mangled worlds" go anywhere?
"Mangled worlds" is an idea from Robin Hanson that attempts to explain the origin of the Born rule. AIUI, it asserts that interpreted as in MWI, decoherence of a superposition as a result of ...
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Why do particles tend to collapse to *energy*-eigenstates (rather than some other basis)?
My understanding from reading about quantum mechanics is that the state of a particle such as an electron can be kept in a superposition of energy states for an extended period of time, when it is not ...
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What is Decoherence? [duplicate]
What precisely is decoherence? Assume familiarity with the density matrix formalism of quantum mechanics.
I read this related question, but I am looking for a more precise answer than the one given. I ...
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Quantum Coherence [closed]
Coherence is a term frequently used in quantum mechanics. However, I struggle to get the bigger picture. In fact, it seems like some definitions contradict each other. Could someone provide a basic ...
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How does a heat bath measure a system?
In the information theoretic treatment of say, the canonical ensemble, one must maximise the Shannon entropy
$$ S =-\sum_i p_i \ln p_i$$
where $p_i$ is the subjective probability for occupying state $\...
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Why is it that we cannot detect any interference after decoherence?
If we assume the many-worlds interpretation of quantum physics is true, what exactly happens during decoherence, that makes it impossible for the different worlds to create interference with each ...
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Transition from Coherent to Incoherent Light / Partially coherent Light for Imaging
I want to know how to model partially coherent/incoherent light for imaging applications.
Usually, you find mathematical treatments of imaging just for the extreme cases.
For the coherent light, there ...
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Why does permanent magnet not exhibit macroscopic quantum effect?
Permanent magnets are a result of quantum mechanics, i.e. quantum spin of electrons inside the magnet aligning.
Quantum spin follows the uncertainty principle. If I measure the spin orientation first ...
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Decoherence time for a voluntary action?
In the thought experiment of Laplace's demon, one talks about an omnipotent being who if he/she knows about all the initial conditions of this world (if the world is considered classical fundamentally)...
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Why does the Lamb-Dicke parameter decrease with the number of ions in an ion chain
I would like to understand (ideally with a nice pedagogic reference), why the fidelity of quantum gates in long ion chain decreases with the number of ions in the chain.
In this reference, it is ...
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Deriving the dephasing operator in the master equation for atom laser interactions
Consider a two level atom where the two levels of the atom are seperated by energy $\hbar\omega_{0}$ and are coupled via the dipole interaction induced by interaction with a laser of fluctuating ...
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Decoherence time of quarks
I have been reading papers on using top quark's use as a probe for new physics using quantum information theoretic observables such as concurrence. One of the reasons they provide for using a top ...
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Decoherence of one-photon states
Let $\rho_1$ be the pure one-photon state described by the ket
$$|\psi_1\rangle = \int dk\ A(k)a^\dagger(k)|0\rangle$$
for a complex amplitude function $A(x)$ and an empty ket $|0\rangle$. This state ...
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What would macroscopic quantum interference look like?
I've heard that the reason we don't see quantum effects at the macroscopic level is because of decoherence.
But I don't know what quantum effects at the macroscopic level would even look like... So I ...
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Decoherence paper, incomprehensible claims
I am reading the paper "The quantum-to-classical transition and decoherence"
by Maximilian Schlosshauer (https://arxiv.org/abs/1404.2635).
I doubt the most basic claims in this paper.
The ...
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Classical limit of quantum mechanics from decoherence or diminishing hbar?
Two pictures regarding the classical limit of quantum mechanics. One says in path integral take hbar to zero then the paths constructively interference near the classical path and the paths deviate ...
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Can the collapse of the wave function be modelled as a quantum system on its own?
Imagine I have an observer $\mathcal O$, a quantum system $\mathcal S$ with Hilbert space $V_{\mathcal S}$, a Hamiltonian $H$, a self-adjoint operator $A$ acting on $V_{\mathcal S}$. The system is in ...
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Does Decoherence explain why constituents of composite systems in textbook Statistical Mechanics are assumed to occupy energy eigenstates?
This question is based off of the first chapter of Pathria's text on Statistical Mechanics.
Consider the system of an Ideal Gas. Consider the system to be in some macrostate specified by $(N, V, E)$. ...
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Do "cross terms" in a state operator necessarily correspond to a coherent superposition?
In his discussion (Chapter 9.2-9.3) of the measurement problem, Ballentine says "any terms [in the state operator $\rho$] that [are] nondiagonal [in terms of having "mixed projectors" $|...
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If only one part of a macroscopic object interacts with the environment, does it affect the non-interacting part?
In a state of quantum coherence, if only a part of a macroscopic object interacts with the environment, does the non-interacting part also have an effect? Does the part that interacts with the ...
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Copenhagen Interpretation vs Quantum Decoherence? [closed]
I'm learning about Quantum Mechanics, and have a question about the Copenhagen Interpretation. It states that the act of observation collapses the wave function. It seems many people take this to ...
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Is there a detailed balance solution for the Lindblad equation
It is known that the Lindblad equation is a master equation.
Does there exist a general approach to a detailed balance condition/solution for this equation?
Please either kindly provide the solution ...
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What is wrong with decoherence? [closed]
One possible explanation of the quantum to classical transition, or in other words of why we don't see macroscopic quantum effects naturally, is environment induced decoherence.
Basically, the system ...
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Decoherence, "nonobservability of superpositions" and measurements on qubits
Observation:
Due to decoherence, the reduced density matrix of a system that has interacted with an environment might look like this:
$$a_0a_0^*|0\rangle\langle 0|+a_1a_1^*|1\rangle\langle 1|+$$
$$...
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Why are accessible states taken as eigenstates in statistical physics? Is the resolution via decoherence?
See for example this question or the answers to this question, neither of which seem to say exactly why the system Hamiltonian eigenstates (and not some other complete basis) are used. It is ...
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Interpreting a complex decoherence factor with length 1
Let's say for a specific simple decoherence model you end up with the following density matrix for the "system" (I will use the common separation in "system" and "environment&...
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Can a non-macroscopic object have mass?
According to this resource from John Boccio:
Consider a body at rest on surface of Earth. Imagine that it shifts
about vertically ever so slightly. Because it has done so, it has
moved to a slightly ...
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Why does Sean Carroll claims that decoherence explains world branching in the Everett interpretation?
In a recent talk, Sean Carroll explicitly claims that, in Everett, world branching
occurs when two decoherence makes worlds "so different" that interference will
no more become observable ...
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What defines "minimal coherence" as a condition for the emergence of stationary interference in a chaotic wave field?
Consider the following observations:
A superposition of two electromagnetic waves with different frequencies will never produce visible interference patterns. Such waveforms will produce ...
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Quantifying coherence with density matrices
I'm aware that the coherence of a statistical ensemble can be measured by looking at the off-diagonal elements of its density matrix, which is computed as the weighted sum of the density matrices of ...
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From Lindblad operators to Kraus operators: an explicit example of a dephasing noise model
I'm trying to understand how to obtain a set of Kraus operators from Lindblad master equations. For a $1$-qubit dephasing noise model, it is well-known that the set of Kraus operators is $\{ \sqrt{p}I,...
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Decoherence of a laser beam via oil emulsion
This is sort of a followup to an earlier question that I posted regarding how to destroy the temporal and/or spatial coherence of a laser beam. It was suggested to me that I could use a rapidly ...
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Interpreting a Density Matrix Resulting from Decoherence of a generalized GHZ State
This questions extends on this question and on the given answer.
What this question is about:
Decoherence model. Consider a simple decoherence process modelled by $$\mathcal{E}\left(\rho\right)=p_0\...
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Decoherence via environmental photons
I am reading the book "Decoherence and the Quantum-to-Classical Transition" by Maximilian A. Schlosshauer, and I have come to understand that for a two-level system with eigenstates $|a\...
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Dephasing noise as a decoherence model - Effect on a generalized GHZ state
Some input:
Consider a decoherence process modelled by $$\mathcal{E}\left(\rho\right)=p_0\rho+(1-p_0)\sigma_z\rho\sigma_z$$ with $p_0=(1+e^{-\gamma t})/2$. One can readily find that this leads to $\...
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Lindblad equation from microscopic principles for free particles with momentum interactions
I'm rather familiar with the formalism of quantum master equations, but I'm struggling with deriving from microscopic principles the collapse operators for a particular case I need.
I consider two ...
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Why is there non-zero probability for a particle to "escape" completely from a solid? [closed]
Let's consider a particle (electron or proton) in a "macroscopic" solid.
Outside of the solid, the state of the particle would have a higher energy.
Because of the conservation of energy, ...
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Does quantum mechanics require classical mechanics for its own formulation?
Is true that quantum mechanics requires classical mechanics (as a limiting case) for its own formulation?
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Molecules are made up of numerous subatomic particles, so don't they constantly interact? How can we achieve quantum coherence? ($\rm C_{60}$)
Since $\rm C_{60}$ is a molecule made up of numerous subatomic particles, no matter how separated from the environment, the interaction between $\rm C_{60}$'s subatomic particles inevitably causes ...
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Does the inside of a solid object not interact with the outside environment? But how does quantum decoherence happen?
We have learned that quantum decoherence is caused by interaction with the environment. However, inside our body, there is no interaction with photons or air molecules in the environment, so how does ...
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What is decoherence important for?
Decoherence has several important applications or is important in not only one way. There is the theoretical (and now also practical) interest in the quantum-to-classical transition. There is it's ...
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How to understand the frequency picking in spin-boson model in the Born-Markov limit?
I have been reading the book Decoherence and the quantum-to-classical transition by Maximilian Schlosshauer, section 5.3.2
A classical example is the spin-boson model which has the following ...
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