Quantum mixed states enable deterministic energy transfer without entropy

A peer-reviewed theoretical study led by City University of Hong Kong researchers has identified a quantum mechanism that could transfer energy from fluctuating sources without transferring entropy. The work, published in Physical Review Letters under the title “Nonunique Decompositions of Mixed States and Deterministic Energy Transfers,” centers on a property of quantum mechanics known as the non-unique decomposition of mixed states. The researchers report that this property permits a source to send energy to a “harvester” in a deterministic way, even though the transfer can proceed through several different quantum state transitions. The study does not demonstrate a physical energy-harvesting device; instead, it establishes a theoretical protocol and points to a possible route for reducing losses in low-power technologies.

Energy harvested from natural or ambient sources is often accompanied by entropy, which the news release describes as randomness. That randomness can make it difficult to convert irregular energy into the predictable electrical power required by batteries, sensors and electronic devices. The researchers set out to examine a protocol intended to overcome this obstacle. Their proposed starting point was to show that deterministic energy harvesting, or DEH, might be impossible, but their analysis instead produced what the team described as a viable quantum solution. Professor Oscar Dahlsten, Associate Professor in CityUHK’s Department of Physics and leader of the research team, said the change in direction—from attempting to prove a limitation to uncovering a possible solution—was among the project’s most surprising developments.

The key feature is that a mixed quantum state can have more than one valid decomposition. In the proposed protocol, a quantum harvester can be charged through multiple pathways corresponding to different intermediate superposition states. If the energy source induces any one of those state transitions, the harvester reaches the same charged final state with certainty. This is why the protocol is described as deterministic: the route taken through the intermediate states may differ, but the final outcome does not. The source can therefore trigger a predictable transfer of energy without a corresponding transfer of entropy. The release presents this as a possible mechanism through which different source states could deliver energy in a controlled manner while avoiding the associated randomness.

The framework offers a theoretical foundation for converting ambient energy into usable power with minimal loss. The researchers suggest that it may eventually inform technologies with lower losses than conventional alternating-current-to-direct-current rectifiers. Potential application areas include Internet-of-Things devices, wearable technologies, smart-city sensors and 6G devices that might draw power from ambient sources. These possibilities remain prospective rather than demonstrated: the supplied evidence concerns the analysis and formulation of a quantum transfer protocol, not a laboratory prototype, field trial or human-facing energy system. The work also indicates that the protocol’s relevance to practical harvesting would require further research and experimental development. The study was supported by a Research Grants Council General Research Fund.

Subject of Research: A theoretical quantum protocol for deterministic energy transfer without entropy

Article Title: CityUHK researchers shatter physical limitations and reveal a quantum pathway to entropy-free energy transfer

Article References: CityUHK researchers shatter physical limitations and reveal a quantum pathway to entropy-free energy transfer. Original publication (Bibliographic details unavailable.)

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Keywords: quantum energy transfer, mixed quantum states, entropy, deterministic energy harvesting, quantum physics, ambient energy, energy conversion, low-power devices, Physical Review Letters, CityUHK, researchers, shatter