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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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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Does quantum decoherence happened in the process towards thermal equilibrium?

In Kardar's "statistical physics of particles" and some other books about statistical physics I've read, when dealing with quantum statistics, they just give the conclusion that the density ...
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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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Why is a CPMG sequence more resilient to errors in the pulse amplitudes than a CP sequence?

In the context of NMR (or in general qubits nowadays), a CP sequence is a refocussing sequence that looks like X/2 - X^n - X/2. A CPMG sequence instead is X/2 - Y^n - X/2. This change of axes is in ...
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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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How do different $|\text{Alive}\rangle+|\text{Dead}\rangle$ kind of states behave under decoherence?

I am looking for literature that investigates said behaviour for spins. So far I found many papers on how to measure the macroscopicity of states and therefore a classification of macroscopic states. ...
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The quantum-measurement limit of decoherence

What this question is about: (Simple) models that show that decoherence is the reason for the non-observability of superpositions of macroscopic states use the simplification, that the Hamiltonian ...
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Vanishing off diagonals means non observability of quantumness - But aren't superposition always non observable (in pointer basis)?

Let's take a look at two states, described by $$\rho_{A1}=p_{c0}|0\rangle\langle0|+p_{c1}|1\rangle\langle1|$$ and $$\rho_{A2}=p_0|0\rangle\langle0|+p_1|1\rangle\langle1|+\sqrt{p_0p_1}|0\rangle\langle1|...
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Does quantum decoherence desctibe a deterministic universe?

QM describes a system, whose state evolve unitarily, which is deterministic. The apparent non-determinism comes from the measurement problem, where the state is projected to some subspace in a ...
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How to compute the exact universe branches in many worlds interpretation?

Many worlds interpretation says that, whenever a system's state gets decohered over time, such that no interference between the decohered states is possible anymore, the universe branches, with there ...
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Why doesn't environmental decoherence completely prevent from happening the quantum tunnelling of macroscopic objects? [duplicate]

A macroscopic object has the order of Avogadro’s number of particles. That’s over $10^{23}$. So the probability of all of them tunneling, at the same time, is on the order of that original small ...
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Isn't it inaccurate to use the Schrödinger equation to find the probability that a macroscopic object will undergo quantum tunneling?

Since Schrödinger's equation doesn't show wavefunction decay or quantum decoherence, isn't it inaccurate to calculate the probability that a person or macroscopic object will quantum tunneling? I ...
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Does pure state dephase or decohere?

I know that from the fundamental postulates of quantum mechanics, the norm of state must be preserved under time evolution. But today, I heard some mysterious comment that pure state, the state which ...
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Will quantum events ever occur on a macro-scale rather than a vacuum? Michio kaku says there's a chance we'll wake up on Mars tomorrow

https://www.theatlantic.com/science/archive/2018/10/beyond-weird-decoherence-quantum-weirdness-schrodingers-cat/573448/ In this post, it is shown that quantum decoherence in the macro world occurs ...
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Is measurement or interaction what collapses that wavefunction?

I'm very confused about what exactly causes the wavefunction collapse. I was under the impression that quantum objects propagate as waves and interact as particles. That is, upon interaction with ...
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Is there a quantum interpretation which holds that quantum mechanics completely cease to apply at a certain level?

An interpretation which holds that there is a sharp threshold between quantum objects and classical objects. If there is such an interpretation: how is the threshold itself explained in the framework ...
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Why extremely tiny (but still visible with the naked eyes) objects do not quantum tunnel? [duplicate]

What is the reason that we don't see such objects quantum tunnel? Decoherence? If YES, at what "level" does the decoherence completely suppress quantum tunnelling? Where is the "...
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Looking for proof/derivation for non-zero off-diagonal terms in density matrix as a characterization of interference

Is anyone capable of giving a rigorous derivation of why non-zero off-diagonal terms in the density matrix of a quantum system written in a spesific observable basis characterize the possibility of ...
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The collapse of Wave function isn't a physical process - but then why hasn't everything blurred into complete uncertainty?

Sabine Hossenfelder very coherently points out the "The real problem with quantum mechanics" in the following clip: https://www.youtube.com/watch?v=LJzKLTavk-w&t=583s Shortly after ...
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In real life, for a tennis ball to go through a wall, does it have to completely prevent the particles from interacting? (decoherence)

In real life, for a tennis ball to go through a wall, does it have to completely prevent the particles from interacting? What would happen if we tried infinitely in the real world, where the ...
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Do things and people in the macro world maintain a quantum decoherence? Or do you repeat quantum coherence and quantum decoherence every moment? [duplicate]

Does quantum decoherence remain uninterrupted for things and people in the macro world? Does the interaction of particles occur permanently without interruption in the macro world? Is that why our ...
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