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What Does "Macroscopic" Mean in Macroscopic Quantum Tunnelling? A Terminology Note

DR. ZULFIQAR ALI KHAN

Published Oct 20, 2026• 0 citations
Publisher

Abstract

The 2025 Nobel Prize in Physics honours the discovery of macroscopic quantum tunnellingand energy quantisation in an electric circuit. This note asks what the word “macroscopic” refersto. We distinguish three readings: the physical size of the device, the thickness of the barrier,and the nature of the tunnelling variable. In current-biased Josephson-junction experiments thebarrier that is crossed is not the nanometre-thick oxide layer, whose pair tunnelling underliesthe Josephson effect recognised in 1973. It is a barrier in the effective potential of a collectivephase variable that describes billions of Cooper pairs. We argue that “macroscopic” is best readas describing this variable, and that this reading is consistent with the temperature-independentescape rate observed at low temperature. We also note that “macroscopic” has no single sharpdefinition. The note is a clarification and reports no new results.

DOI
10.5281/zenodo.23491997

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The 2025 Nobel Prize in Physics honours the discovery of macroscopic quantum tunnellingand energy quantisation in an electric circuit. This note asks what the word “macroscopic” refersto. We distinguish three readings: the physical size of the device, the thickness of the barrier,and the nature of the tunnelling variable. In current-biased Josephson-junction experiments thebarrier that is crossed is not the nanometre-thick oxide layer, whose pair tunnelling underliesthe Josephson effect recognised in 1973. It is a barrier in the effective potential of a collectivephase variable that describes billions of Cooper pairs. We argue that “macroscopic” is best readas describing this variable, and that this reading is consistent with the temperature-independentescape rate observed at low temperature. We also note that “macroscopic” has no single sharpdefinition. The note is a clarification and reports no new results.
AbstractThe 2025 Nobel Prize for quantum tunneling in an electrical circuit andthe 1973 Prize for tunneling phenomena in solids share the same mechanism:tunneling through a thin oxide barrier described by Josephson equations.The 1973 mechanism was correctly monitored as micro. In 2025, thebarrier remains ∼ 10−9 m, the chip remains micro-fabricated, and the particleremains a Cooper pair. Only the external circuit was enlarged.The phenomenon is correct and the mechanism is correct, but the label”Macroscopic Quantum Tunneling” is incorrect. A micro-based tunnelingevent does not become macroscopic by enlarging its wires. The correct termis enlarged micro tunneling.
FINDING: 2025 Nobel Prize in Physics awarded for macroscopic quantum tunnelling — the demonstration that quantum behaviour (superposition, tunnelling) persists in superconducting circuits large enough to be held in the hand. | MATH: Tunnelling probability through a barrier: T ≈ exp(−2∫√(2m(V(x)−E))/ħ dx). Macroscopic circuit regime governed by the Josephson relations: I = I_c sin(φ), dφ/dt = 2eV/ħ. Quantised energy levels in the "phase particle" potential U(φ) = −E_J cos(φ) − (ħ I_ext/2e)φ. Escape rate from a metastable well (Kramers/quantum regime): Γ ∝ exp(−B/ħ) where B is the Euclidean action of the bounce solution. | CONNECTION: The Josephson phase φ is a compact U(1) variable — a circle S¹. The washboard potential is a cosine lattice, i.e. a 1D periodic structure with the same translational symmetry class as crystallographic lattices. The tunnelling action B/ħ is dimensionless and scales with the ratio of barrier height to plasma frequency ω_p = √(2eI_c/ħC). No direct 0.618/1.618 Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
The Nobel laureates of this year have devised an experiment to observe macroscopic quantum tunneling in an electrical circuit made of superconductors. This monumental discovery has sparked numerous innovations and ultimately earned the three pioneers the Nobel prize. Afterwards, superconducting circuits play a key role in the proliferation of quantum technology in the 21st century. Especially, in the heart of the 2nd quantum revolution, quantum information technology is based on the radical development of the quantum computers. Superconducting Josephson junction devices has been the most advanced technology that has been picked up by the global tech giants in quantum computing. I will briefly review how the superconducting quantum chips and the macroscopic quantum effect had led innovation in quantum technology afterwards.
The 2025 Nobel Prize in Physics recognizes a conceptual shift that has been more than a century in the making: the transition from observing quantum phenomena in materials to deliberately engineering quantum behaviour in macroscopic electrical circuits. Awarded to John Clarke, Michel Devoret, and John Martinis, the prize honours the experimental demonstration and control of macroscopic quantum tunnelling and energy quantization in superconducting circuits. Their work resolved a long-standing question at the heart of quantum mechanics: can an object large enough to wire, probe, and manipulate behave as a single quantum system? The answer, now unequivocally, is yes.
On 7 October 2025, the Royal Swedish Academy of Sciences awarded the NobelPrize in Physics to John Clarke , Michel H. Devoret , and John M.Martinis "for the discovery of macroscopic quantum mechanical tunnellingand energy quantisation in an electric circuit" (Physical Review Letters 55,1543 and 55, 1908, 1985). Their experiments demonstrated that quantumeffects — tunnelling through energy barriers and occupying discrete quantisedenergy levels — are not confined to the subatomic world but operate inmacroscopic systems large enough to be held in the hand. This paperdemonstrates that the 2025 Nobel Prize provides direct experimental supportfor seven foundational elements of the Quantum Ocean hypothesis (Parts 27–34). Specifically: (1) The discovery that quantum behaviour emerges as thedefault when decoherence is removed validates Part 27's foundational axiom(Quantum is the Default). (2) The observation of macroscopic quantumtunnelling validates the mechanism by which universes nucleate in thequantum ocean (Coleman-De Luccia vacuum decay, Part 30). (3) Themeasurement of quantised energy levels in macroscopic circuits validates theΩ-quantum model of discrete internal states (Part 32). (4) The collectivequantum behaviour of trillions of Cooper pairs acting as a single quantum entityvalidates the ocean's behaviour as a collective quantum system (Part 29). (5)The Josephson junction — two superconductors separated by a thin insulatingbarrier through which quantum effects propagate — is a laboratory-scalestructural analogue of the bubble wall separating universe from ocean (Part30). (6) The tilted washboard potential governing the Josephson junction isstructurally identical to the false vacuum landscape governing bubblenucleation. (7) Martinis's subsequent invention of the superconducting qubitand his leadership of Google's quantum computing program (Sycamore 2019,Willow 2024) demonstrates a direct causal chain from the Nobel discovery tothe quantum computers our framework identifies as ocean probes (Part 28).Five elements across Parts 27–32 are upgraded from [P] Plausible to [E]Established (Nobel-validated). 🌌 Interactive Space Research Assistant: Explore and ask questions about this research interactively with the Quantum Ocean Framework Ai Chat (or talk directly with the Quantum Ocean Framework Ai voice conversation).
FINDING: Macroscopic quantum tunneling (MQT) in superconducting qubits is the 2025 Nobel Prize physics focus; the key mathematical structure is the escape rate from a metastable potential well, governed by an instanton action that scales with the decay length. | MATH: The MQT rate is Γ=Aexp⁡(−Sinst/ℏ) \Gamma = A \exp(-S_{\text{inst}}/\hbar) Γ=Aexp(−Sinst​/ℏ), where Sinst S_{\text{inst}} Sinst​ is the Euclidean action. For a cubic potential V(q)=12mω02q2−λq3 V(q) = \frac{1}{2}m\omega_0^2 q^2 - \lambda q^3 V(q)=21​mω02​q2−λq3, the decay length ℓ=ℏ/2mΔU \ell = \hbar / \sqrt{2m\Delta U} ℓ=ℏ/2mΔU​ (where ΔU \Delta U ΔU is barrier height) enters as Sinst=365ΔUω0 S_{\text{inst}} = \frac{36}{5} \frac{\Delta U}{\omega_0} Sinst​=536​ω0​ΔU​. The qubit's Josephson energy ratio EJ/EC E_J/E_C EJ​/EC​ sets the effective mass; the crossover from quantum to thermal regime occurs at T∗=ℏω0/(2πkB) T^* = \hbar \omega_0 / (2\pi k_B) T∗=ℏω0​/(2πkB​). | CONNECTION: The decay length ratio ℓ/Δqzero-point \ell / \Delta q_{\text{zero-point}} ℓ/Δqzero-point​ (zero-point width Δq0=ℏ/(2mω0) \Delta q_0 = \sqrt{\hbar/(2m\omega_0)} Δq0​=ℏ/(2mω0​)​) yields \( \ell/\Delta q_0 = \sqrt{\Delta U / (\hbar \o Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com