Measurement-powered Tunneling Engines Enable Simultaneous Cooling and Power Generation Via Virtually Occupied States

Quantum tunneling, the ability of particles to pass through seemingly impenetrable barriers, forms the basis of a new approach to energy manipulation, as demonstrated by Rafael Sánchez from Universidad Autónoma de Madrid, Alok Nath Singh from University of Rochester, and Andrew N. Jordan and Bibek Bhandari from Chapman University. This team explores how performing a measurement on a tunneling particle fundamentally alters its energy, allowing them to construct ‘tunneling engines’ that harness the very act of observation to generate power and achieve cooling. The researchers reveal that these devices can operate in a unique hybrid mode, simultaneously producing energy and lowering temperatures, and even achieve refrigeration driven solely by a temperature difference, eliminating the need for external power sources. Importantly, the study also identifies a surprising phenomenon where measurement noise actually enhances system stability, paving the way for novel quantum control strategies and demonstrating the complex, dual role of measurement in quantum systems.

Hybrid Quantum Thermal Machines with Quantum Dots

This research investigates quantum thermodynamics in extremely small systems, specifically those built from quantum dots, and explores the design of hybrid quantum thermal machines. These machines combine different quantum components and exploit quantum effects to enhance performance in cooling, heating, and energy conversion. The work focuses on creating devices capable of performing multiple thermodynamic tasks simultaneously, a key goal for developing more versatile and efficient quantum technologies. Researchers are particularly interested in understanding how these systems behave when they are not in thermal equilibrium, as most real-world devices operate under these conditions.

The study employs theoretical modeling to describe the dynamics of these quantum systems. Scientists demonstrate that a triple quantum dot system can achieve enhanced thermodynamic performance compared to classical systems, due to the exploitation of quantum effects. They identify key parameters that control the performance of the thermal machine and provide guidelines for optimizing these parameters, suggesting the potential for multifunctional devices that can perform multiple thermodynamic tasks simultaneously.

Measurement Drives Cooling and Power Generation

Scientists have developed a novel approach to harness quantum measurement for both power generation and cooling, creating what they term “tunneling engines. ” This work exploits the fundamental principle that measuring the position of a particle tunneling through an energy barrier alters its energy state, enabling simultaneous cooling and power generation, a hybrid regime previously unexplored. The study pioneered a method for measurement-assisted autonomous refrigeration and “checkpoint” cooling, achieved solely through a thermal bias without requiring an applied potential. Detailed analysis revealed a “purification-by-noise” effect, where the measurement process drives the system into a stationary dark state, effectively purifying the quantum state. The team meticulously investigated the interplay between particle transport, generated power, and heat exchange with the detector, demonstrating that power generation coincides with a specific condition where the occupation of the central dot transitions from virtual to real. This precise control over quantum states and energy transfer represents a significant advancement, opening new avenues for designing efficient quantum thermal machines and exploring the fundamental role of measurement in quantum mechanics.

Quantum Dot System Generates Power and Cools

Scientists have demonstrated a novel quantum device, a triple quantum dot system, capable of simultaneously generating electric power and providing cooling, leveraging the principles of quantum measurement. The work centers on exploiting the tunneling of electrons through a potential barrier, where a position measurement fundamentally alters the energy of those electrons. This allows the device to function as an engine, extracting energy from the measurement process itself. Experiments reveal that the system can operate autonomously, meaning it requires no external applied potential to function, relying solely on a thermal bias to drive both power generation and cooling.

The team engineered a system where electrons tunnel between two outer quantum dots via a central dot, which is also coupled to a charge detector. When electrons virtually occupy the central dot during tunneling, the detector registers their presence, leading to a measurable current. This current constitutes the generated power. Importantly, the device achieves a hybrid regime, enabling simultaneous cooling and power generation. Measurements confirm that the system’s performance is characterized by the ratio of useful output to the heat transferred during the measurement process. Researchers discovered that the measurement process drives the system into a stable “dark state,” unaffected by the detector, allowing for dynamic stabilization even with all reservoirs in equilibrium.

Quantum Tunneling Drives Work and Cooling

This research demonstrates the potential of quantum tunneling to perform work and achieve cooling, establishing a novel approach to quantum thermodynamics. Scientists have shown that by measuring the position of an electron tunneling through a barrier, they can manipulate its energy, effectively harnessing the measurement process itself as a means to generate power and drive refrigeration. The team designed a triple quantum dot system where a central dot facilitates electron transfer between two outer dots, and demonstrated that detecting the presence of an electron in this central dot alters its energy state, enabling both power generation and cooling simultaneously. Furthermore, the researchers discovered that the measurement process can drive the system into a stable, low-energy state, even with all components at the same temperature.

This suggests that carefully controlled measurements can not only extract work but also actively stabilize quantum systems. The authors acknowledge that their model relies on specific conditions, including strong Coulomb interactions and a significant energy detuning between the quantum dots, which may limit its direct applicability to all systems. Future work will focus on exploring the robustness of these effects in more complex systems and investigating the potential for scaling up these devices for practical applications in quantum technologies and energy harvesting.