| Mar 30, 2026 |
A research team has identified environmental interactions as the cause of ultrafast electronic decoherence in solids, a long-standing open question in quantum physics.
(Nanowerk News) A physics team at DGIST has identified the microscopic mechanism responsible for the ultrafast loss of quantum coherence in solid materials, a question that had remained unanswered despite extensive worldwide research.
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The discovery, published in the journalAdvanced Science (“Superradiance and Broadband Emission Driving Fast Electron Dephasing in Open Quantum Systems”), explains why quantum states in real-world open environments collapse within mere femtoseconds and could help close the gap between theoretical quantum models and practical quantum technologies.
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Key Findings
- The team pinpointed environmental interactions, specifically superradiance, as the dominant cause of ultrafast electronic decoherence in solids during high-order harmonic generation.
- A newly developed computational method based on the Lindblad master equation enabled precise modeling of both electron–electron and electron–environment interactions.
- The researchers found that interference between superradiance and broadband emission leads to mutual cancellation, a previously unrecognized effect that governs how quantum order breaks down.
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When intense laser light strikes a solid material, it can produce what physicists call high-order harmonics. These harmonics are valuable both scientifically and industrially because they enable material characterization and the generation of ultrafast pulses and high-energy light.
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Yet the process comes with a persistent complication: the quantum states of electrons in the material lose their coherence within just one to two femtoseconds, a timescale of 10⁻¹⁵ seconds. Despite extensive investigation worldwide, no one had been able to explain why this decoherence happens so rapidly.
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The core difficulty lies in the nature of real quantum systems. No quantum system in the physical world is perfectly isolated from its surroundings. Every material interacts with an environment of neighboring particles, lattice vibrations, and electromagnetic fields. Standard quantum mechanical models, which tend to treat systems as closed, have struggled to capture these environmental effects with enough precision to explain the observed decoherence timescales.
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The research was led by Professor JaeDong Lee of DGIST’s Department of Physics and Chemistry (DGIST President Kunwoo Lee). His team tackled the problem by developing a new computational framework built on the Lindblad master equation. Unlike conventional quantum master equations, this approach can account for both the interactions among electrons within a material and the interactions between those electrons and their surrounding environment. This dual capability proved essential for uncovering the mechanism at work.
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Using this framework, the researchers analyzed two phenomena that occur during high-order harmonic generation in solids: superradiance, a collective emission effect driven by environmental coupling, and broadband emission. They discovered that these two processes interfere with each other, effectively canceling one another out. This interference, which had not been identified before, turned out to be the key factor driving ultrafast electronic decoherence.
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The finding confirms that open quantum environment effects, rather than purely internal electronic dynamics, are the dominant force behind the rapid loss of quantum coherence in solids. This distinction matters because most existing quantum technology concepts assume isolated or near-isolated quantum systems, an assumption that does not hold in practice.
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“Through this study, we have found that ultrafast electronic decoherence in solids—long regarded as a mystery for over a decade—originates from environmental interactions in open quantum systems,” stated Professor JaeDong Lee of the Department of Physics and Chemistry at DGIST. “The true significance of this research lies in opening a pathway to connect ideal quantum theory to practical and reliable quantum engineering, and it will pose a new and substantial challenge to existing quantum technology concepts based on the assumption of isolated quantum systems.”
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Since perfectly isolated quantum systems cannot exist in reality, the results directly challenge frameworks that rely on that assumption. By showing precisely how and why coherence collapses at femtosecond timescales under real conditions, the study reframes ultrafast electronic decoherence from an unexplained obstacle into a quantifiable, environment-driven process.
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