The Spectral Birth of Irreversibility and the Arrow of Time

Gerald F. Thomas

Mikhail Nitsberg

The primary objective of the experiment is to reliably identify the critical threshold at which quantum coherence collapses. Detecting this threshold is fundamental: it marks the birth of the arrow of time and the transition from unitary quantum dynamics to irreversible dissipation. In the proposed protocol, the threshold is determined by measuring the interference fringe contrast V while systematically varying the microsphere mass; its value (Dcrit = 2,863 µm, Mcrit = 27,04 pg) provides a clear boundary between the “quiet zone” (coherence preserved) and the regime of plastic flow of the vacuum (irreversible coherence loss). Without a robust determination of this threshold, any tests for irreversibility or control of the arrow of time are physically meaningless. An experimental protocol is proposed for direct laboratory testing of the hypothesis of a fundamental yield limit of the physical vacuum — a critical value of gravitational self-energy E_max ≈ 2.05 × 10⁻³² J at which the reversible elastic deformation of the vacuum (GR metric) transitions to irreversible plastic flow. The protocol is based on measurements of the free oscillation ringdown of the center of mass of levitated fused silica (SiO₂) microspheres in a diamagnetic trap at cryogenic temperatures. A precision scanning grid of eight steps is constructed in the diameter range 1.0–5.0 µm with a critical point D_crit = 2.863 µm and critical mass M_crit = 27.04 pg. The key prediction is a slope kink in the contrast function V(M) at the threshold point, experimentally distinguishable from the smooth monotonic decay predicted by the Penrose– Diósi and GRW/CSL models. Below the threshold — a flat zone of silence (V = 1); above — decay of V according to the law exp(−x(x − 1)), where x = E_G/E_max. At the threshold point V = 1 (flow is just beginning), while Penrose gives V = 1/e ≈ 0.37. Distinguishable. The exponent 1/3 in the formula for E_max is not a fitting parameter. It is uniquely determined by the dimensionality of space and does not yield a macroscopic, experimentally accessible threshold for any other value of d. The central goal of the protocol is to investigate the birth of the arrow of time at the transition point. The protocol consists of two parts: a bottom-up pass (birth of the arrow) and a top-down pass (test of irreversibility). An additional test — rotation of the sphere at the moment of threshold crossing — examines the connection between parity and the direction of the arrow (TP-invariance). The window for controlling the direction is the interval from M_crit to 1.4 × M_crit, where dissipation is already underway but the flux is weak and the direction has not yet frozen. The model is falsifiable by three independent criteria: • A flat zone of silence at small D. • V ≈ 1 at the threshold point. • Quadratic decay above the threshold. The use of diamagnetic levitation instead of an optical tweezer eliminates the dominant decoherence channel — photon scattering from the trap. At pressure P = 10⁻¹³ mbar and trap frequency f₀ = 1 Hz, the background decoherence is ~1% of the threshold (signal-to-background ratio ~100). At f₀ = 100 Hz — 0.01% (signal-to-background ratio ~10,000).

Xi Ming, Qing-yu Cai

This work investigates the fundamental connection between quantum mechanics and thermodynamics through the concept of the arrow of time. While the second law of thermodynamics identifies the arrow of time with the monotonic increase of entropy in isolated systems, closed quantum systems evolve unitarily and conserve von Neumann entropy, making the origin of irreversibility less apparent. Here we establish a no-go theorem proving that correlations in unknown states of closed quantum systems cannot be universally removed by any physical operation. This result demonstrates that correlation generation is inherently irreversible, providing a microscopic and universal basis for the arrow of time. In thermodynamic settings, this irreversibility ensures that heat flows spontaneously from hotter to colder subsystems, reproducing the Clausius formulation of the second law. More generally, the irreversible growth of correlations explains entropy increase, the approach to equilibrium, and decoherence as observable manifestations of the same principle. Our findings ground a quantum-mechanical foundation for the second law of thermodynamics and demonstrate the universality of the arrow of time.

Wojciech Hubert Zurek

Arno Böhm, Ioannis E. Antoniou, Piotr Kielanowski

The exponential decay (or growth) of resonances provides an arrow of time which is described as the semigroup time evolution of Gamow vector in a new formulation of quantum mechanics. Another direction of time follows from the fact that a state must first be prepared before observables can be measured in it. Applied to scattering experiments, this produces another quantum mechanical arrow of time. The mathematical statements of these two arrows of time are shown to be equivalent. If the semigroup arrow is interpreted as microphysical irreversibility and if the arrow of time from the prepared in-state to its effect on the detector of a scattering experiment is interpreted as causality, then the equivalence of their mathematical statements implies that causality and irreversibility are interrelated.