Questions tagged [quantum-tunneling]
Quantum tunneling is a classically-forbidden quantum effect that allows a bound object with energy less than the boundary to penetrate it with a small probability. A notable example is $\alpha$-decay
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Gravity cause wavefunction collapse? (Roger penrose) [closed]
Roger Penrose suggested that gravity might play a role in the collapse of the wave function (which describes a system as a superposition of multiple values of Position, momentum etc.). According to ...
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Is it possible that when measured more than one Cooper pair will have tunneled across the junction?
If I've understood the idea correctly a charge qubit is formed by a superconducting island coupled by a Joseph junction to a superconducting reservoir. The state of the qubit is determined by the ...
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Can quantum tunneling of some sort allow 2 solids which dont touch each other to have the same chemical potential?
Suppose we have 2 solids seperated by a distance x.If the distance x is in the quantum range(10-20 atoms) even though the solids dont touch each other would their Fermi levels become the same after ...
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Moving Mott Transition Tunnels
I have a question on moving tunnels. Let's assume you have a wrapped semiconductor by a piezolectric material that creates a series of staggered mott transitions along the conductor. Each mott ...
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How do protons fuse in the sun?
I know that Nucelar fusion in the sun requires quantum tunneling to occur, as otherwise the Sun's core wouldn't be hot enough to overcome the Fusion barrier.
However while the 2nd and further stage of ...
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How hot would the sun have to be to work without quantum tunnelling
I know that the Nuclear fusion in the sun would not work without quantum tunnelling, as the nuclei wouldn’t ever have enough energy to overcome the potential barrier.
So how hot would the sun have to ...
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Zener diode reverse bias I(V) equation
What is the equation for the reverse bias current in terms of voltage applied? And this even be analytically derived? If so, how to derive it.
I can't seem to find good resources on this topic.
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How does shape of a wavefunction changes as it encounters a potential barrier?
A particle of mass and energy $E > 0$ in one dimension is scattered by the potential
below
If the particle was moving from $x = -\infty$ to $x= +\infty$, which of the following graphs gives
the ...
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Why the wave function decays exponentially when it crosses the potential barrier?
That may be an obvious question, but I would like a physical answer, not math.
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Alpha decay must be quantum tunnelling. Why?
By measuring the energies of the emitted alpha particles, how can we say that they have energies less than the height of the nuclear potential well when they are inside the well? How can we be sure ...
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Can't find any QTC (quantum tunneling composite)
As per the title, I can't find any QTC to buy online. I may be dumb or just looking in the wrong places. Is it that uncommon? Are there any places that sell it locally in Melbourne, or is it just ...
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Can a brane contain different Calabi-Yau compactifications in various areas?
In Brian Greene's book The Hidden Reality he discusses the string landscape, and the possibility of it leading to a multiverse. In short, a universe with 3 large dimensions such as ours would contain ...
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What is difference between Ferroelectric Tunneling Junctions (FTJs) and Ferroelectric capacitors (FeCaps)?
Aren't Ferroelectric Tunneling Junctions (FTJs) and Ferroelectric capacitors (FeCaps) just ferroelectric materials sandwiched between 2 metal electrodes, with only difference being in the thickness of ...
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Why do we interpret transmission and reflection coefficients as probabilities?
In standard 1D textbook step potential problems, for $E>V_0$ with $V_0$ the step potential for $x>0$, one finds that for $x<0$ that eigensolutions are of the form
$$\psi(x) = A_1e^{i\sqrt{2ME/...
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For a particle in a 1D box, what is the expectation value of momentum for a particle that has tunnelled through the walls and escaped?
For a particle in a box, where the walls of the box have a finite (i.e. not infinite) potential
energy, what is the expectation value of the momentum of a particle which has tunnelled
through the wall ...
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What are the exact relations between bound states, discrete spectra, and negative energies in quantum mechanics?
Consider the nonrelativistic quantum mechanics of one particle in one dimension ("NRQMOPOD") with the time-independent Schrodinger equation
$$
\left( -\frac{\hbar^2}{2m} \frac{d^2}{dx^2} + V(...
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P-n junction diode and tunnelling current [duplicate]
In reverse bias p-n junction diode, why the tunnelling current cannot be explained by accounting the particular electrons which have enegy higher than the barrier's energy?
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Reverse bias p-n junction diode and Kinetic energy
In reverse bias p-n junction diode, which energy is lower than the energy of the potential barrier: the average kinetic energy of the would-be-tunnelling electrons or the kinetic energy of the ...
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Quantum tunnelling of an electron in ground state
I asked my question on Quora and i got various conflicting answers. So, I decided that here I could get a definite answer. Unless the question is not too vague.
According to quantum mechanics, is ...
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Tunnelling explained by time-independent Schroedinger equation
I am a retired theoretical physicist. I am currently trying to promote the exact sciences by helping highschool students with their mathematics, physics and chemistry studies. One student, who is in ...
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WKB approximation derivation for $E<V$
I understand that we can write any complex wavefunction on polar form $A\exp(iθ)$ with both $A,θ$ real. Following the logic of Griffiths on WKB (here, page 291):
We write the energy wavefunction in ...
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In reverse bias p-n junction diode, how do one know that the kinetic energy of the tunnelling electron is lower than the energy of the barrier? [duplicate]
In reverse bias p-n junction diode, how do one know that the kinetic energy of the (thermally generated in the p-side) tunnelling electron is actually lower than the energy of the barrier (the ...
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In the Esaki diode, how can one be 100% sure that there are tunnelling electrons with lower energy in comparison with the barrier's energy?
In the tunnel diode, if it is all about the statistical accumulation/distribution, how can one be certain that there are electrons with lower energy (in comparison with the barrier's energy) which ...
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In the Esaki diode, how do physicists measure/estimate the velocity of a would-be-tunneling electron?
Layman's explanation, please. Let's consider an Esaki diode.
How do physicists measure/obtain the velocity of a would-be-tunneling electron in order to justify the claim that the potential barrier is ...
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Is there real physical possibility for a "macroscopic" object to undergo quantum tunnelling? [duplicate]
According to quantum mechanics, there is fantastically (astonishingly, astronomically, infinitesimally, ridiculously etc.) small probability for a book on a table to quantum tunnel through the table.
...
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Will the probability for tunnelling go completely to zero? [closed]
According to quantum mechanics, the probability for quantum tunnelling (of an object) never become completely zero, no matter how "big" is the height and the thickness of the barrier.
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Zener breakdown - a quantum mechanical derivation
In §6.8 of Ziman's "Principles of the Theory of Solids" he derives the imaginary component of the wave vector of an electron inside an energy gap (due to action of an electric field). He ...
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Electronic tunneling between two states
I am reading Steering Electrons on Moving Pathways (Beratan et al. 2009) which is about electron tunneling in biomolecules, and specifically the processes via which an electron can move from an ...
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Can a particle experience tunneling even if its energy is higher than the barrier? [closed]
I know that quantum tunneling can make particle go through the barrier even when its energy is not enough, but dose it happen when the particle's energy is higher than the barrier? Will it go through ...
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How to Understand Quantum Phase Slips in Josephson Junction Array in terms of Tunneling?
I am trying to understand quantum phase slips in terms of quantum tunneling between the minima of the Josephson potential (see page 2 right before equation (1)). Consider the following circuit diagram ...
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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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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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What would be a probability of a silicon atom from the moon to quantum tunnel to earth?
What is the probability of a silicon atom going from the moon and landing on the Earth? The reason is that there is a barrier that the silicon atom has to cross which is the moon's own gravity so that ...
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Has quantum tunnelling of an atom ever been empirically confirmed?
The phenomenon first drew attention in the case of alpha decay, in which alpha particles escape from certain radioactive atomic nuclei.
But has scientists ever observed quantum tunnelling of an atom? ...
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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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With the tunnel effect, because matter travels through solid matter, why wouldn't teleportation be possible? [duplicate]
The tunnel effect is when quantum particles sometimes go through a solid object.
If this is possible, then teleportation between, say portal locations throughout the earth, should be possible.
Why or ...
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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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Is there a quantum interpretation according to which quantum tunnelling is impossible at certain level?
Is there a quantum interpretation according to which quantum tunnelling becomes physically impossible at certain (macroscopic) level?
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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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How can quantum tunneling happen conceptually?
I have read in Griffiths' Quantum Mechanics that there is a phenomenon called tunneling, where a particle has some nonzero probability of passing through a potential even if $E < V(x)_{max}$.
What ...
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Is quantum uncertainty of particle location bound by the speed of light?
If I measure the location of a quantum particle and then measure its location 1 second later, is there a probability larger than zero that I find it in a location farther away from the first location ...
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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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All matter will turn into Fe-56?
from what I understand, fe-56 is the most stable configuration of matter and therefore over time, so Dyson in "Time without end: Physics and biology in an open universe", thanks to quantum ...
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Alpha particles and quantum tunneling
collapse and revival
There are a few things that I quite didn't understand about the tunneling of alpha particles.
Where does the kinetic energy of the alpha particle comes from? Is it because of the ...
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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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Relation between tunneling current and fermi golden rule (Bardeen model)
I am looking into the paper of Tersoff and Hamann - Theory of the scanning tunneling microscope.
In this one there is the tunnel current written as
$$I = \frac{2\pi e}{\hbar} \sum_{\mu ,\nu} f(E_\mu) [...
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Does quantum tunneling result in the collapse of the wave function?
Does quantum tunneling itself result in the collapse of the quantum object's wave function? So, as a hypothetical scenario, suppose you have a two-slit experiment, but instead of two slits, you have ...
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Definition of transmission and reflection coefficients for a particle
Quick intro:
A 1D quantum particle is subject to the potential
$$
V(x) = \begin{cases}
0 \;\;\;\;\; x\leq 0\\
V_0 \;\;\; x > 0
\end{cases}
$$
I am trying to understand the definition of ...
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Momentum conservation in correlation functions
In Mahan "Many particle physics" the following Hamiltonian is considered in studying electron tunnelling through a junction
\begin{equation}
H_t = \sum_{kp} T_{kp} c^\dagger_k c_p + h.c.
\...
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Why is the resolution of a tunneling microscope not limited by the wavelength of the electrons?
Why is the resolution of a tunneling microscope not limited by the wavelength of the electrons? Is it impossible for the electrons that are tunneling across the gap to appear somewhere in the gap, ...
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