Hainan University Theory Links Time's Arrow to Irreversible Quantum Correlations

The fundamental question regarding the irreversible progression of time has long presented a challenge to physics. Researchers at Hainan University in China, led by physicist Cai Qingyu, introduced a novel theoretical framework published near the end of 2025 that offers a quantum-mechanical explanation for the 'arrow of time.' This perspective complements the established Thermodynamic Arrow of Time, which is rooted in entropy, by focusing on the internal dynamics of quantum systems and the rate at which quantum correlations increase.

Classical mechanics and relativity laws historically permitted the theoretical reversal of time, yet everyday experience demonstrates an undeniable irreversibility. Cai’s team mathematically demonstrated through a 'no-go theorem' that once two quantum particles establish a connection, akin to an information 'handshake,' no physical process can erase or recover the initial information of those particles, regardless of their surrounding environment. This non-recoverable transfer of information is posited as the mechanism creating the automatic, unidirectional nature of temporal passage.

This theory distinguishes itself from prior hypotheses, such as those involving quantum 'decoherence' where increasing entanglement with the environment dictates time's direction. Instead, Cai’s work grounds the arrow of time in the irreversible recording of the correlation itself, rather than relying on external observation. Senior theoretical physicist Sun Changpu from the Chinese Academy of Sciences acknowledged the research as a significant advancement, noting it addresses one of science's most profound questions by bridging quantum mechanics and lived experience.

The concept of time's asymmetry, first formalized by Arthur Eddington in 1927, contrasts with the time-symmetric nature of fundamental laws like Newton's laws or the Schrödinger equation, which function equally well when time is mathematically reversed. While Boltzmann's entropy concept explains macroscopic irreversibility, it is considered inadequate at the microscopic level because it relies heavily on probability and the universe's initial conditions. Cai's work, focusing on closed quantum systems, offers an internal explanation for temporal directionality arising from the system's structure.

Further experimental support for the non-static nature of time's apparent stability comes from studies demonstrating irreversible quantum correlations in open quantum systems. For instance, research has shown that by controlling quantum correlations, scientists can induce a temporary reversal of the thermodynamic arrow, such as making heat flow from a cold body to a hot one, which underscores that the arrow of time is relative to initial conditions. The mathematical 'no-go theorem' utilized by Cai's team is conceptually related to other foundational theorems in quantum information, asserting that quantum information cannot be arbitrarily duplicated or destroyed, only redistributed. This new theory establishes the trajectory of existence as the singular trajectory of time, rooted in the fundamental quantum mechanics of particle interaction.