#quantumtunnelling

Researchers Measure Hydrogen Quantum Tunnelling in Palladium Crystal: Atoms Pass Through Walls. New research confirms the fundamental quantum mechanics principle at the atomic level. Hydrogen Quantum Tunnelling in Palladium Crystal Materials science and quantum technology advanced when researchers accurately observed hydrogen atom quantum tunnelling in a palladium crystal lattice. This event proves that hydrogen atoms in crystals may “tunnel” over energy barriers, something traditional physics says is impossible. Results improve understanding of hydrogen's atomic-level diffusion and quantum nature.

Quantum Tunnelling News

In quantum mechanics , “quantum tunnelling” allows subatomic particles to traverse energy barriers without energy. Because quantum particles are wave-like, they can exist in several places, making this seemingly impossible feat attainable. Particle tunnelling depends on transmission coefficient, particle mass, energy, barrier height, and width. Calculate the probability amplitude of particle detection in a region using the time-independent Schrödinger equation.

Friedrich Hund proposed quantum tunnelling in 1927 to explain alpha decay. In the 1930s, George Gamow used it to explain nuclear processes and prove that a particle's probability of passing through a barrier is not zero even if its energy is less than the barrier's height Giaever and Esaki showed electron tunnelling through thin insulating layers between metals in the 1950s and 1960s. Gerd Binnig and Heinrich Rohrer's 1981 STM sees atoms using tunnelling current.

Quantum tunnelling is critical in many chemical reactions, notably those involving light atoms like hydrogen, where it can slow reaction speeds. In addition to imaging. Transferring protons or electrons may aid enzyme catalysis and DNA mutation. For low power and fast switching, transistors and tunnel diodes need it.

Innovation in Energy Storage

Energy storage is one of the most intriguing quantum tunnelling applications because it can create devices with unprecedented performance.

Ultra-capacitors: Scientists have proven that quantum tunnelling can be used to create nanoscale ultra-capacitors with power and energy densities up to 100 Wh/kg. Creating incredibly thin dielectric layers with high electrical charge storage achieves this.

Quantum tunnelling allows nanoscale electrodes with huge surface areas, improving supercapacitors' energy storage capacity.Tunnelling supercapacitors are 50 Wh/kg.

Lithium-ion batteries: Quantum tunnelling can create nanoscale electrodes with large surface areas to improve electric car and portable device cycle life and charging speed.

Tunnelling allows nanoscale electrodes with huge surface areas, improving fuel cell performance, durability, and power density.

A revolutionary energy storage device called a "quantum capacitor" manipulates quantum states through quantum tunnelling to store electrical energy.

Challenges in Quantum Interpretation: Tunnelling Time

On July 10, 2025, Charles Blue of Phys.org highlighted a Nature paper on an experiment that directly contradicts a novel Bohmian physics prediction, a distinct interpretation of quantum theory. This experiment investigates the controversial “quantum tunnelling time debate”.

Copenhagen Interpretation vs. Bohmian Mechanics:

Subatomic particles are waves of probabilities until they are detected, when their waveform collapses into a particle, according to the Copenhagen interpretation.

According to Bohmian mechanics, particles remain point-like and are positioned by “hidden” variables that cannot be measured. Their paths are guided by a "pilot wave," creating wave-particle duality.

Even if they make similar predictions, these perspectives characterise particles' fundamental nature differently. Bohmian mechanics defines tunnelling time clearly by assuming deterministic particle trajectories. The average time transmitted Bohmian trajectories spend inside the barrier zone is this “trivial” definition.

Test of the Bohmian Prediction: A tunnelling quantum particle would be “at rest” inside an infinitely long barrier, meaning its dwell time would be unbounded.

The Experiment and Results:

Researchers simulated an infinite photon barrier by sandwiching specially constructed mirrors with a bottom mirror engraved with a nanoscale ramp and parallel waveguides. Lasers on the ramp regulated photon momentum.

Photons tunnelled into the barrier and a secondary waveguide, allowing constant speed bouncing to determine speed.

This time element and photon decay rate inside the barrier were used to calculate dwell time.

The limiting dwell duration contradicts the Bohmian prediction of limitless stay time. The researchers said their findings “contribute to the ongoing tunnelling time debate and can be viewed as a test of Bohmian trajectories in quantum mechanics,” noting that the “measured energy–speed relationship does not align with the particle dynamics postulated by the guiding equation in Bohmian mechanics”.

Impact on the Debate: This study puts doubt on Bohmian mechanics, although its conclusions are not conclusive because the experiment was analogue and relied on assumptions. The common view of the “tunnelling time problem” struggles to specify how long a particle stays within a barrier if it is moved, making it a contentious issue in physics. The popular belief that a particle is a distributed superposition of probability amplitudes until it is measured causes this difficulty. In this context, asking about a “eventually transmitted” particle's “history” before its collapse into a transmitted state is “ill-posed”.

The role of weak measurement Some authors, like Steinberg, provide poor measurement approaches to extract tunnelling time. These minimally intrusive observations are used with postselection of final states (e.g., transmitted particles) to answer subensemble questions without wavefunction collapse. The Nature experiment used a weak measurement approach comparable to the Larmor clock. Detractors say weak measurements use probability amplitudes instead of probabilities, which might generate “unreasonable” or complex values that are hard to physically understand. Therefore, poor measurement delivers a “perspective,” not a “resolution,” to tunnelling time.