01/16/2026
This is a major breakthrough
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🕰️ For the first time, physicists have unified space and time in quantum mechanics—bridging a century-old divide in physics.
Assistant Professor Seok Hyung Lie from UNIST and collaborator Professor James Fullwood from Hainan University have developed a revolutionary theoretical framework that treats quantum correlations across both space and time within a single mathematical structure.
Published in Physical Review Letters, their breakthrough resolves a fundamental disconnect: while Einstein's relativity seamlessly unifies space and time into spacetime, traditional quantum theory has always described spatial systems with quantum states (density matrices) but temporal evolution through entirely different mathematics (quantum channels).
The team's innovation introduces "multipartite quantum states over time," which allows the entire timeline of a quantum process to be described as a single quantum state. By starting from just two foundational assumptions—linearity of the initial state and quantum conditionability (a quantum version of classical conditional probability)—they proved that the mathematical structure of these spacetime quantum states is uniquely determined.
Remarkably, the framework connects directly to Kirkwood-Dirac quasiprobability distributions, already established in quantum physics literature. This linkage suggests that recent experimental techniques like quantum snapshotting can now probe temporal quantum correlations with unprecedented precision. The method enables researchers to analyze both spatially separated quantum systems and temporally separated quantum processes using identical mathematical language for the first time.
The implications extend far beyond pure theory. This unified description could accelerate progress in quantum information science, quantum measurement theory, and even efforts to reconcile quantum mechanics with general relativity—one of physics' deepest unsolved problems. By treating time as fundamentally quantum rather than merely classical, the framework offers new pathways toward understanding how quantum systems behave across spacetime's full fabric.
đź“„ RESEARCH PAPER
📌 Seok Hyung Lie et al, "Multipartite Quantum States over Time from Two Fundamental Assumptions", Physical Review Letters (2025)