Recent advancements in quantum physics have unveiled significant insights into the nature of entropy and its implications for quantum information processing (QIP). A research team at TU Wien, Austria, published findings on January 29, 2025, clarifying the relationship between quantum systems and the second law of thermodynamics. Traditionally, this law states that entropy in closed systems tends to increase, leading to disorder. However, the study shows that when entropy is defined in a manner compatible with quantum principles, it also increases in quantum systems, aligning with thermodynamic expectations.
Professor Marcus Huber and his team demonstrated that low Shannon entropy states evolve into higher entropy states over time, confirming that quantum systems do adhere to thermodynamic laws under specific conditions. This understanding is crucial for developing new quantum technologies, particularly those involving many-particle systems, where reconciling quantum theory with thermodynamics is essential.
On the same day, another groundbreaking study reported real-time observations of ultrafast optical Einstein-Podolsky-Rosen (EPR) correlations, a fundamental resource for QIP. Researchers achieved this feat using a 6-THz-bandwidth waveguide-based optical parametric amplifier, enhancing the efficiency of 70-GHz-bandwidth homodyne detectors, which are integral to 5G telecommunications. This innovation allows for quantum state measurements at unprecedented speeds, marking a shift from nanosecond to picosecond timescales.
The observed quantum correlation of 4.5 dB below the shot-noise level in wavepackets with a 40 ps period showcases the potential for scaling up entangled states for various QIP applications, including quantum computation and secure communication. The compatibility of this technology with existing optical communication frameworks suggests a seamless integration into future quantum networks.
These discoveries not only advance theoretical understanding but also pave the way for practical applications in quantum technologies, enhancing the efficiency and speed of quantum information systems globally.