New research identifies fundamental limits on the reliability of quantum batteries and shows how charging strategies can balance high power with stable energy and power delivery. The findings represent an important step toward the future development of practical and useful quantum energy-storage devices.
Quantum uncertainty sets a fundamental trade-off in quantum batteries, limiting their ability to deliver both stable power and reliable energy at the same time.
Quantum batteries are an emerging area of research, with progress being made through theoretical studies and proof-of-principle experiments in small quantum systems. Unlike conventional chemical batteries used in everyday life, they use quantum systems to store and transfer energy. They are being explored as potential future energy sources for quantum processors and other quantum technologies. Previous research has focused mainly on how fast and powerfully quantum batteries can be charged.
In the new research, the researchers establish fundamental limits on fluctuations in both the energy delivered by a quantum battery and the rate at which it is delivered. The work, Fundamental Limitations on the Reliabilities of Power and Work in Quantum Batteries, was newly published in PRX Quantum.
“A quantum battery ideally should not only be fast and powerful but also needs to charge or deliver energy in a reliable and stable manner at the same time. Our work shows that quantum mechanics places fundamental limits on the reliabilities of quantum batteries,” says Brij Mohan, Postdoctoral Researcher at the University of Oulu and first author of the study.
The researchers show that the well-known quantum-mechanical uncertainty relation prevents fluctuations in delivered energy and power from both being made arbitrarily small at the same time, meaning that reliable energy delivery and stable power cannot be achieved simultaneously. In this context, reliability and stability mean keeping these fluctuations small compared with their respective average values. This fundamental trade-off arises because work and power are represented by non-commuting operators in closed quantum batteries, much like position and momentum in quantum mechanics.
The team then studied how this trade-off depends on the way many quantum battery cells are charged. In parallel charging, cells operate independently. In collective charging, all cells participate together. Hybrid charging lies between these two extremes, with groups of cells interacting during charging. The results show that stronger collective charging increases power but also increases power fluctuations, thereby reducing power reliability. This indicates that maximum power alone is not sufficient for assessing quantum-battery performance.
“Our results show that there is a meaningful way to balance power enhancement and the reliability of work and power. Intermediate-range interactions based charging scheme can provide a useful compromise between high power and stable operation,” says Tanmoy Pandit, VTT, Espoo, Finland.
The researchers also examined quantum batteries with transverse Ising-like many-body interactions and found the same qualitative power–reliability trade-off, indicating that the effect is not restricted to the simplest theoretical model. “The reliability limits connect quantum fluctuations with many-body quantum physics in a direct way. They provide useful charging strategies that are practically advantageous,” says Manabendra Nath Bera, IISER Mohali, India.
“Quantum batteries offer a fascinating link between quantum information, thermodynamics, and many-body physics. Understanding their fluctuations is essential if these systems are eventually to become useful technological resources,” says Maciej Lewenstein, ICFO, Spain.
The researchers next aim to investigate the reliability limits in more realistic settings, including noise, dissipation, open-system dynamics, and experimentally relevant quantum platforms.
Quantum batteries are a continuation of the long-term research carried out by the University of Oulu’s Nano and Molecular Systems Research Unit into the modelling and theory of quantum devices, such as superconducting qubits and quantum processors.