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.

learn more… | top users | synonyms

0
votes
0answers
42 views

Proof of Tridecompositional Uniqueness Theorem (Elby and Bub, 1994)

I'm looking for a proof of the Tridecompositional Uniqueness Theorem (Elby and Bub, 1994). Could someone help me? References: Maximilian Schlosshauer, arXiv:quant-ph/0312059; p.12-13. A. Elby &...
0
votes
1answer
37 views

Probabilities with the Density Matrix

The density matrix of the system is given by: $$ [\rho_{S}(t)]_{mn} = [\rho_{S}(0)]_{mn} e^{-i\omega_{0}(m - n)t} e^{-i \delta(t)(m^2 - n^2) - \gamma(t)(m - n)^2}, ...
0
votes
0answers
17 views

The Hamiltonian of the Spin-Boson Model

I came across the following two specifications of the spin boson model with weak system-environment coupling: Dissipative/Population Decay Model: $$ \mathcal{H} = \frac{\omega_{0}}{2}\sigma_{z} + ...
2
votes
0answers
98 views

What is the influence of QED vacuum in electron-double-slit experiments?

In a recent question on superpositions of different quarks it was explained, that the superpositions of different electric charged particles cannot exist, in contrast to strangeness quantum number. It ...
4
votes
2answers
325 views

Transition from one state to another in Quantum Mechanics

When we measure an electron's position we know that the wave function $\psi$ peaks at the measured position and the wave function as a function of momentum is a harmonic function. When it makes the ...
0
votes
1answer
63 views

Quantum entanglement and affecting the particles [duplicate]

I am trying to grasp some aspects of the quantum entanglement, but the existing resources (including some of the links here) seem a bit confusing. I am trying to find an answer to the following ...
1
vote
1answer
48 views

What is an incoherent state?

I am reading through a recent paper which speaks frequently of "incoherent states" without ever defining what such a state is. I gather from the context of the paper that it has something to do with ...
2
votes
1answer
44 views

Meaning of non diagonal terms in decoherence

It is my understanding that the non-diagonal terms in the density matrix of a macroscopic system that it is initially in an entangled state go exponentially fast to zero as the system interacts with ...
1
vote
2answers
75 views

Variation of schrodinger cat replaced by quantum computer

In the "classical" imaginary Schrodinger's cat experiment, which seems to be no longer serious, or at least irrelevant, by many (some?) people, everything is explained away by decoherence. Now, let ...
0
votes
0answers
28 views

How is the lifetime of a symmetric and antisymmetric state determined by its constituents

In the context of quantum mechanics, there is the concept of so called symmetric and antisymmetric states, which can have multiple constituents. A type of hybridized state, if you will. To keep the ...
3
votes
2answers
77 views

Simple question about decoherence

In simple terms, decoherence is the mechanism through which a quantum system in superposition that interacts with the environment undergoes a quick "apparent collapse" and is no longer found in ...
14
votes
2answers
2k views

Is the preferred basis problem solved?

Once and for all: Is the preferred basis problem in the Everettian Interpretation of QM considered solved by decoherence or not? THere are a few people who claim that it's not, but it seems the vast ...
4
votes
2answers
187 views

What events lead to quantum decoherence?

Is there a very specific definition for all types of events where quantum decoherence occurs? Is it merely any event that is "thermodynamically irreversible" and/or "causes entropy to increase"? Is it ...
-1
votes
1answer
53 views

Implications of weak measurement on entanglement

What are the implications of weak-measurement on entangled particles, and how does that resolve the problem of non-superluminal quantum "communication"? If I understand correctly, entangled particles ...
1
vote
0answers
39 views

Schrödinger's cat experiment in the context of decoherence

I am trying to visualize in more detail the Schrödinger's cat experiment in the context of decoherence. Please let me know if the description below makes sense or is somehow flawed. If the ...
0
votes
1answer
74 views

Exact solution of Qubit Decoherence using Transfer Matrix

I'm going through a particular paper on decoherence: Exact Solution of Qubit Decoherence models by a transfer matrix method I'm having trouble understanding a particular step in the mathematics ...
10
votes
1answer
238 views

Did Leggett and Caldeira solve the measurement problem?

In 1983 Leggett and Caldeira published a paper (see also here) that shows the evolution of the density matrix in a dissipative system. Follow-up work by Zurek and others shows the relevance to ...
3
votes
2answers
121 views

When does the world split in MWI

I've been reading Eliezer Yudkowsky's blog post regarding decoherence and many worlds, and although he is not a physics but a strong proponent of MWI, I can basically see why he feels that MWI is a "...
6
votes
1answer
61 views

If all the particles of a Bose-Einstein condensate become entangled with each other,does the system still remain a Bose-Einstein condensate?

I know that an entangled system is found in a single entangled state and that when you try to observe the individual state of a particle from an entangled system using a reduced density matrix, you ...
1
vote
1answer
30 views

Modelling the onset of decoherence in a subspace as a transition out of the subspace

http://arxiv.org/pdf/0903.3297v1.pdf I am currently reading papers discussing the Zeno Effect. The linked paper discusses modelling a transition out of a wanted subspace as the onset of decoherence. ...
4
votes
1answer
71 views

Decoherence Free Subspaces and how they stay this way, using the Zeno Effect

I am currently reading papers discussing the Zeno Effect, which discuss how measuring a system at high frequencies can almost freeze the state of a system, or keep the system in a specific subspace of ...
2
votes
2answers
137 views

Meaning of “realism” in quantum mechanics

When physicists doing work in quantum measurement, decoherence, Bells' inequalities etc. use the term "realism" what exactly do they mean? I'm looking for answers targeted towards, say, someone whose ...
5
votes
5answers
1k views

Is the wave function of a particle re-created after a measurement stops?

Yeah, I haven't quite understood, or been told, what happens to, for example an electron and its wavefunction, when you stop to measure it. I mean, an electron has a wave function describing its ...
0
votes
3answers
67 views

Einselection locality in decoherence theory

Consider two polarity-wise entangled photons A and B in an EPR experiment. The process of measuring the polarization of photon A by Alice is described by the decoherence of the 2-photons system ...
2
votes
2answers
50 views

Can decoherence occur just by simple reflection?

I create an entangled photon pair. One photon is sent inside a resonant cavity which reflects the photon many number of times. Will there be decoherence between photon in the resonant cavity and its ...
0
votes
0answers
22 views

Can particles recohere after measurement?

I try to elaborate the relation between decoherence and the ouputs problem. Talking about the Stern-Gerlach experiment Caldeira writes here: "Recovery of coherence should be achieved simply by ...
5
votes
2answers
415 views

How is decoherence due to the environment compatible with the Copenhagen interpretation?

Let's say that "decoherence" is that transition from a pure quantum state to a mixed state due to interactions with the environment. (A reasonable definition?) How is that compatible with the ...
3
votes
2answers
145 views

Conservation of quantum coherence?

Is coherence conserved under unitary transformation? As we saw in the process of generating entanglement, coherence between states of the subsystem is transferred to quantum correlations (related to ...
1
vote
0answers
40 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 ...
3
votes
5answers
669 views

How does a Wavefunction collapse?

I have been wondering and researching... How does a wavefunction collapse into one state?More specifically, what conditions cause a wavefunction for a quantum particle to collapse? Does this have to ...
1
vote
0answers
41 views

Continuous spectra and quantum decoherence

Suppose that some quantum wave function $\psi = \int a_i \,i\rangle \,\,di$ where pseudo-spanning ket "vectors" of $\psi$, $i \rangle$, are continuous. (thus the use of integral.) By normalization, $...
7
votes
1answer
231 views

Reason for decoherence time's dependence on variables?

Zurek 2001 is a review article on decoherence in quantum mechanics. Equation 5.36 on p. 24 gives an estimate of the decoherence time, which I'll paraphrase as follows: $ \frac{t_D}{t_R} = \left(\frac{...
4
votes
0answers
86 views

Decoherence and interpretations

With quantum decoherence, are there still any "gaps" in our knowledge of quantum mechanics that hint (either in terms of the physics, philosophy, or otherwise) at the need for further interpretation? ...
0
votes
0answers
15 views

Resources on estimation of environment model for environemnt induced quantum decoherence

I am curious to see what literature exists about estimation of a quasi-classical environment interacting with a quantum system causing decoherence in system states. There has been in general a lot ...
2
votes
0answers
32 views

What factors affect decoherence times? [closed]

The question say it all. For example is it the mass of the system? The amount of energy? The species of atom? The electric charge?
0
votes
0answers
16 views

Data: decoherence time

Searching for experimental data on decoherence time. For example, this type of data can look like (but is not limited to): atomic species (eg. Carbon) vs. decoherence time. Physics stackexchange ...
1
vote
1answer
39 views

Re-entering superposition

I've realized that I'm somewhat familiar with what happens when an system in a superposition is "measured". But not at all with what happens after. Example: If there is an electron in a superposition,...
4
votes
2answers
164 views

Why doesn't gravity mess up the double slit experiment?

So let's say you are doing a double slit experiment. Also, let's use electrons. My question is, won't the gravity of the electron affect the earth, thereby causing it decoherence and its wave ...
2
votes
1answer
160 views

are there known fundamental limits of quantum computer scaling?

Quantum computers provide exponential speedup relative to classical computers. However, it is empirical fact that increasing of number of qubits makes the the computer harder and harder to keep ...
2
votes
0answers
46 views

How does gravity affect entanglement?

Hypothetically an entangled pair of atoms are placed inside two similar satellites orbiting at the same altitude, one of the satellite will then slow its speed and descend towards the surface of Earth....
0
votes
0answers
33 views

Collisional decoherence and trajectories

The density matrix of a mesoscopic particle subjected to collisional decoherence satisfies the equation $$ i\frac{\partial \rho(x,x',t)}{\partial t}= \frac{1}{2m}\left (\frac{\partial^2}{\partial x'^...
0
votes
0answers
63 views

Decoherence in the long time limit of density matrix elements

For a state $$ |\Psi(t)\rangle = \sum_{k}c_k e^{-iE_kt/\hbar}|E_k\rangle, $$ the density matrix elements in the energy basis are $$ \rho_{ab}(t) = c_a c^*_be^{-it(E_a -E_b)/\hbar} $$ How is it that ...
0
votes
0answers
47 views

Why decoherence?

Why do we study decoherence? I mean the postulates of quantum mechanics agree with experiments perfectly and we all know how a superposition state looks like, for example the spin-z up state is ...
3
votes
3answers
192 views

Wave function collapse and Schrodinger's equation without measurement

Will wave function collapse without measurement? Since all matters are described by wave functions, then in principle, I should be able to describe wave function collapse by Schrodinger's equation. (...
0
votes
0answers
36 views

Is the wavefunction of particles inside a gas spread or localized?

For an individual free particle that starts localized, the wave function packet spreads over time, so the particle becomes less localized. Suppose now that we have a gas of those particles inside a ...
1
vote
2answers
101 views

Theoretically, how does quantum decoherence induce noise?

The decoherence process has allowed us to explain various (classical and decoherence) sources of measurement noise in quantum systems. I intuitively understand this physical concept of decoherence-...
13
votes
2answers
664 views

Are Thomas Breuer's subjective decoherence and Scott Aaronson's freebits with Knightian freedom the same things in essence?

In his remarkable works (1,2 and their recent development 3) Thomas Breuer proves by diagonalization the phenomenon that the observer cannot distinguish all phase space states of a system where he is ...
4
votes
3answers
828 views

Does decoherence explain all instances of wave function collapse?

Specifically, how can decoherence explain the appearance of flecks of metallic silver on a photographic plate when exposed to the very weak light of a distant star? EDIT: Perhaps the advocates of ...
1
vote
2answers
322 views

Atomic natural line width

In laser cooling, with a model of a 2-level atomic system, spontaneous emission is stated to be dependent on the "natural line width" of the excited state of the atom. This width is defined as the ...
0
votes
0answers
45 views

Derivation of the dynamical master equation for collisional decoherence of a massive particle

I'm working on the problem of collisional decoherence of a massive particle interacting with an environment of light particles. The problem. I have some confusion regarding the derivation of the ...