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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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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At what "level" does the environmental decoherence completely surppress quantum tunnelling?

In this regard, is it possible for an extremely tiny (but still visible with the naked eye) object to perform spontaneous quantum tunnelling despite of the fact that decoherence is at work?
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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 does there seem to be a disconnect between the spatial dependence of the order parameter and spatial dependence of the superconducting gap?

I am studying superconducting bilayers. My understanding is that the superconducting energy gap is the real part of the order parameter. In many theory papers describing S-N or S-S' contacts, they ...
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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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Plotting Quantum Tunneling the real way

Often when looking at Quantum Tunneling graphs something similar is shown: Having an exponentially decaying graph inside the barrier. But these graphs seem to be arranged. There I ask myself how to ...
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Can wrapped D-branes change the cycle they wrap, by quantum effects?

Suppose the internal manifold in a string compactification of type II, say, contains a D-brane wrapped around a given cycle. Is there an obstruction to the brane changing its wrapping cycle via a sort ...
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Can a kink in a finite one dimensional box tunnel into a trivial solution?

Given a simple kink solution of the Sine Gordon equation, is it possible for such a solution in a finite volume to tunnel into a trivial vacuum solution, given that such tunneling demands a finite ...
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When an object interacts with the environment, does the wave function collapse? [duplicate]

When an object interacts with the environment, does the wave function collapse? So macro-world objects and humans cannot accidentally experience quantum events even if they wait for an infinite amount ...
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Can the Pauli exclusion principle and quantum tunneling coexist? [closed]

It is said that quantum mechanics can pass through walls. In addition, there is a possibility that the body will be disassembled and then reassembled. By the way, doesn't Pauli exclusion principle say ...
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In quantum physics, apparently every "particle/wave" is capable of tunneling. Why then is there a shadow at all?

A layman's question: In quantum physics, apparently every "particle/wave" is capable of tunneling/passing through material. Why then is there a shadow at all?
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Mathematical Approximation for Quantum tunnelling

After some long basic algebraic transformation the transmission coefficient $T$ for a matter wave $\psi_1$ with wave vector $k_1 $ travelling with a wave vector $k_2$ through a wall of length $l$ and ...
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What's the meaning of a complex momentum in classical mechanics?

I'm looking at a section of Griffiths and Schroeter's Introduction to Quantum Mechanics, pp. 355. It states a straightforward set of equations that got me thinking about the exact way in which complex ...
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Are quantum events such as decay, emission, absorption and tunneling truly instantaneous or is there some small time period? [duplicate]

Are quantum events such as decay, emission, absorption and tunneling truly instantaneous or is there some small time period? Assuming there is an underlying cause for a quantum event it seems to me ...
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Is the tunnelling effect already naturally accounted for in the density functional theory?

Would it be correct to say the tunnelling effect is already naturally accounted for in the density functional theory or the Hartree-Fock formulation of the many-body problem to the Shrodinger equation?...
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Could electrons tunnel into protons in a white dwarf and turn it into neutron star?

Just like the Sun, where hydrogen ions tunnel into each other to start fusion, which would be otherwise impossible with this level of kinetic energy, could electrons inside a white dwarf tunnel into ...
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Transmission amplitude for asymmetrical potential barrier

The problem is in 1D. So if I have a potential barrier $V(x)$ from $[-a,a]$ where $V(x)$ can be any function (also an asymmetrical function). Is the transmission amplitude for a particle travelling ...
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Can our hand pass through a table?

I recently read that "there is a $1$ in $5.2^{61}$ chance that the molecules in your hand and table would miss each other, making your hand go through it". To me, it seems completely false, ...
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Are virtual states eigenstates of physical observables?

In quantum mechanics, physical observables are represented by self-adjoint operators. A "virtual state" is supposedly a state which is unmeasurable, due to being too "short lived"....
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How to quantum tunnel a human? [duplicate]

I know this is purely theoretical, but I promise it is useful to me. Please reply even if you can answer only some of the points: Is the quantum tunneling probability connected to De Broglie ...
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Does lattice confinement fusion need proton tunnelling to work?

As Lattice confinement fusion (LTC for short) is triggered at relatively small temperatures as compared to more traditional Tokamak methods, it reminded me of the need of quantum tunnelling for ...
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How did physicist calculate times like $10^{1500}$ and $10^{10^{76}}$ years?

If protons don't decay, iron stars are expected to form via quantum tunneling after $10^{1500}$ years, and they are expected to all have become neutron stars or black holes after $10^{10^{26}}$ to $10^...
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What does theory say about tunnelling and universe expansion?

Correct me if I'm wrong, my limited understanding of how wave functions work let me assume that they don't "zero out", unless through interferences. I would then imagine that, when a ...
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Tunnelling of alpha particles - explanation

As it is now known because of Gamow, how alpha decay occurs. We have taught this theory in our class in last week. There we have been introduced with a strange phenomenon happening because of which ...
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Why do we say that quantum tunneling is when a particle passes through a barrier they wouldn't classically have enough energy to overcome?

If a particle is in an energy eigenstate, then it must also be in a superposition of both outside the barrier and inside the barrier. So, if we measure the particle to be outside the barrier, I wouldn'...
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If the universe is infinite, would QM allow the existence of "weird" zones? [closed]

If we suppose that the universe is spatially infinite and extends more or less homogenously in all directions without end (having similar galaxies, stars etc.), then we can assume that there is a more ...
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How to convert the problems of quantum mechanics that we usually solve for plane waves to gaussian wavepackets?

I want to solve a barrier potential problem for a Gaussian Wavepacket moving at a velocity v= $\frac{p_0}{m}$. Normally we consider plain wave functions of the following type $$\Psi (x) = Ae^{ikx} + ...
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Question regarding stopping a quantum tunneling simulation and integrating it

There is this wonderful blog that discusses how to simulate quantum tunneling (https://physicspython.wordpress.com/2019/10/27/quantum-tunneling-part-3/) I am new to using python to do physics, and ...
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Why don't electrons tunnel out of atoms?

The overlap of a free electron wavefunction and a bound electron wavefunction is nonzero. So why don't electrons slowly bleed out of atoms? If any wavefunction enters a free particle state it will ...
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Why is the conductance of a metal-insulator-metal tunnel junction parabolic?

For bias voltages below the tunnel junction barrier heights (and below the Fowler-Nordheim limit), tunnel junctions have a parabolic conductance as a function of bias. Is this due to the metallic ...
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Is muon-catalyzed fusion a form of pycnonuclear reaction?

Muon-catalyzed fusion is a form of fusion where the electron in a hydrogen atom is replaced by a much heavier muon, which orbits 196 times closer than an electron and allows it to approach other ...
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How unlikely is it that particles tunnel (comparatively) very long distances?

My understanding of quantum tunneling is that when you're not measuring a particle's position you can't know exactly where it is, just where it might be, and that sometimes it happens to be on the ...
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Why do helium balloons deflate?

Helium balloons deflate–even when they are made from metal foil. How does this happen exactly? Is there any chance that quantum tunneling plays a role here? The thought is that the helium atoms inside ...
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Tunneling in Infinite potential well [duplicate]

In quantum mechanical tunneling particle doesn't scale the potential but instead find a short route to cross barrier. Then why is tunneling only possible in case of finite square well potential and ...
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Transmission Coefficient of Finite Square Well

Now I was calculating the Transmission Coefficients of finite square well potential and found something weird The transmission coefficient is given by $$T=\left[1+\frac{V_o^2\sin^2(2ka)}{4E(E+V_o)}\...
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Why can't quantum tunnelling carry energy or information faster than light?

A few experimenters have at one time or another claimed that quantum tunnelling allows the transfer of information or energy at superluminal speeds. One was the idea that music was carried across a ...
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