A team of Australian researchers says it has built a quantum “battery” that bucks a basic rule of classical batteries: as it gets bigger it charges faster and stores more energy. The experimental device, described in Light: Science & Applications and led by CSIRO scientist Dr James Quach in collaboration with RMIT University, uses collective light–matter interactions inside a microcavity to produce what the authors call superextensive scaling — performance that improves faster than the system’s size.
The device confines light in a microcavity and couples it strongly to organic molecules such as copper phthalocyanine, creating hybrid light–matter quasiparticles known as polaritons. According to the paper, adding more molecules does not simply increase capacity linearly; instead the coupling strength grows collectively, so energy absorption becomes more efficient as the number of participating molecules rises. “Quantum batteries have this really peculiar property where the larger they are, the less time they take to charge,” Dr Quach said.
In experiments the team observed charging on femtosecond timescales — quadrillionths of a second — and, crucially, found that charging time fell as molecule count increased. Measured stored energy and peak output power also rose with system size, a departure from classical expectations in which energy density typically remains constant while charging time lengthens with capacity. The researchers report that output power increases more than proportionally with the number of molecules, reinforcing the superextensive character of the effect.
A key advance in this prototype is the inclusion of integrated charge-transport layers that allow the device to deliver electrical output, enabling a full charge-and-discharge cycle inside a single quantum device. Earlier laboratory demonstrations of collective charging often stopped at energy storage or theoretical proposals; this design couples the polaritonic system to layers that convert stored excitations into electrical current. The paper also notes that initial excitations evolve into metastable triplet states via intersystem crossing, extending the lifetime of stored energy from femtoseconds to nanoseconds — still brief, but markedly longer than the initial excitation lifetime.
Despite the striking scaling behaviour, the authors caution the prototype’s practical utility is far from realised. The amount of energy stored in the device remains vanishingly small — on the order of a few billion electron volts — and overall efficiency gains are limited. The team does report improved photon-to-charge conversion relative to earlier setups, but substantial engineering work will be needed to increase storage capacity and lifetime to levels useful for applications.
The broader significance of the work is twofold: it offers experimental evidence that collective quantum effects can accelerate charging and increase energy density, and it highlights new avenues — microcavity engineering, choice of molecular absorber, and charge-extraction architecture — for turning quantum-scale phenomena into usable devices. The authors say the findings challenge classical thermodynamic intuition about scaling and point to research priorities such as extending metastable lifetimes, boosting stored energy per unit volume, and improving conversion efficiency if quantum batteries are to move beyond laboratory demonstrations.
For now the study stands as a proof of principle that bigger can indeed be faster in quantum energy storage, but considerable materials science and device-design hurdles remain before such systems could compete with conventional batteries.