Thermal vapor quantum battery based on collective atomic spins
Jinyi Li, Juncheng Zheng, Xue Yang, Kainan Hu, Kanzheng Zhou, Junkai Zhuang, Hengyan Wang, Zhihao Ma
Abstract
Quantum batteries harness non-classical resources, such as quantum coherence and entanglement, to surpass the performance limits of classical energy-storage devices. Here we realize a room-temperature quantum battery based on a collective atomic spin ensemble in a thermal alkali-metal vapor, containing approximately Rb atoms with coherence times exceeding 110 ms. We operationally determine the battery capacity by directly measuring the extremal internal energies accessible under unitary evolution. This tomography-free protocol agrees closely with the conventional state-based definition and verifies the decomposition of capacity into coherent and incoherent contributions. We further show that quantum coherence can substantially enhance the storage capability independently of level populations, and experimentally establish quantitative relations linking battery capacity to von Neumann, Tsallis and linear entropies. By introducing a controlled dephasing channel with a magnetic-field gradient, we observe a monotonic reduction of capacity with coherence loss and track the corresponding evolution of the entropy-capacity relations. Our results identify thermal atomic spin ensembles as a scalable platform for quantum batteries and connect macroscopic quantum energy storage with operational quantum thermodynamics.
AI Impact Assessments
(3 models)Scientific Impact Assessment
Core Contribution
This paper demonstrates a quantum battery implemented in a room-temperature thermal alkali-metal (⁸⁷Rb) vapor ensemble containing ~10¹² atoms with coherence times exceeding 110 ms. The key novelty is threefold: (1) realization of a macroscopic quantum battery operating at room temperature with extensive atom numbers, (2) an operational, tomography-free protocol for determining battery capacity by directly measuring extremal internal energies under unitary evolution, and (3) experimental verification of quantitative entropy–capacity relations and the Pythagorean decomposition of capacity into coherent and incoherent contributions.
The paper addresses a genuine gap in the quantum battery field: prior experimental demonstrations have been limited to small systems (single NV centers, few-qubit NMR, semiconductor quantum dots, superconducting circuits) operating under restrictive conditions (cryogenics, low atom numbers, short coherence times, weak polarization). By leveraging a paraffin-coated vapor cell with near-unity spin polarization and long coherence times, this work demonstrates that thermal atomic ensembles can serve as a scalable, practical platform for quantum energy storage.
Methodological Rigor
The experimental methodology is generally sound. The authors employ well-established techniques from atomic physics—optical pumping, RF spin control, Faraday rotation readout—repurposed for quantum battery characterization. Several aspects merit attention:
Strengths in methodology:
Methodological concerns:
Potential Impact
Within quantum battery theory and experiment: This work significantly advances the experimental state of the art by demonstrating quantum battery concepts at macroscopic scale and room temperature. The operational capacity measurement protocol is potentially transferable to other platforms. The experimental verification of entropy–capacity relations (von Neumann, Tsallis, linear) bridges quantum thermodynamics theory with experiment in a meaningful way.
Broader impact: The connection to quantum thermodynamics is the paper's strongest conceptual contribution. The demonstration that coherence-only battery capacity exists and can be experimentally measured provides concrete evidence for quantum advantage in energy storage. However, the practical implications for actual energy storage are negligible—the stored energy per atom is vanishingly small, and the system's utility is primarily as a testbed for fundamental quantum thermodynamic concepts.
Adjacent fields: The techniques developed here could influence quantum metrology, quantum sensing, and spin-ensemble quantum information processing, where similar platforms are already employed.
Timeliness & Relevance
The paper is timely, arriving amid growing theoretical and experimental interest in quantum batteries (as evidenced by the 2024 Reviews of Modern Physics Colloquium cited as Ref. [1]). The field has been theory-heavy, and experimental demonstrations—particularly scalable ones—are in high demand. Room-temperature operation is a significant practical advantage that distinguishes this work from competing platforms.
The connection to operational quantum thermodynamics addresses a current need to ground abstract thermodynamic inequalities in experimental reality. The entropy–capacity relations had been proposed theoretically (Ref. [44], by some of the same authors), and this paper provides their first experimental verification.
Strengths & Limitations
Key strengths:
1. Room-temperature operation with macroscopic atom numbers—a clear practical advantage over competing platforms.
2. Long coherence times (T₂ ≈ 113 ms) enabling nearly dissipation-free unitary control.
3. Operational measurement protocol that avoids full state tomography—scalable to larger systems.
4. Clean experimental verification of multiple theoretical predictions (Pythagorean decomposition, entropy bounds).
5. Controlled dephasing channel enabling systematic study of coherence degradation effects.
Notable limitations:
1. The system operates as N independent two-level systems with no inter-particle entanglement or correlations. The "quantum" advantage demonstrated is single-particle coherence, not genuinely many-body quantum effects. This is acknowledged implicitly but should be discussed more critically.
2. The effective two-level truncation discards the rich multilevel structure of ⁸⁷Rb, limiting the demonstrated capacity.
3. No charging power measurements are reported—a central quantity in quantum battery theory.
4. The absolute energy stored is impractically small for any real energy storage application.
5. The paper does not explore collective charging advantages (superextensive scaling), which is one of the most theoretically interesting aspects of quantum batteries.
6. Some theoretical relations verified are relatively straightforward for product states of identical qubits; the results would be more impressive for correlated or entangled states.
Overall Assessment
This is a well-executed experimental paper that successfully bridges quantum battery theory with a practical, scalable platform. Its primary contribution is demonstrating that thermal atomic ensembles can serve as a testbed for quantum thermodynamic concepts at macroscopic scale. While the quantum advantage demonstrated is limited to single-particle coherence rather than many-body entanglement, the work opens clear paths toward more sophisticated experiments. The operational measurement protocol and entropy–capacity verification are valuable methodological contributions. The paper is incremental rather than transformative but represents meaningful progress in an emerging experimental field.
Generated Apr 21, 2026
Comparison History (41)
Paper 2 likely has higher impact: it introduces a broadly applicable, statistically principled framework (LIMINAL) for selecting minimal Lindblad models from experimental data, demonstrated on a real five‑qubit superconducting processor and multiple characterization tasks. This directly advances quantum processor calibration, validation, and noise modeling—core bottlenecks for scalable quantum computing—making applications immediate and cross-cutting (control, verification, device engineering). Paper 1 is novel experimentally for quantum batteries at room temperature, but the near-term real-world energy-storage relevance is less direct and the field is narrower.
LIMINAL introduces a systematic, broadly applicable framework for learning and validating open quantum system models of quantum processors—a critical need as quantum hardware scales. Its methodology (likelihood-ratio model selection for Lindblad dynamics) addresses a fundamental bottleneck in quantum computing: accurate device characterization. Paper 2 demonstrates a novel quantum battery platform, but quantum batteries remain largely conceptual with limited near-term practical applications. Paper 1's impact spans quantum computing, error correction, and device engineering, affecting a larger and more active research community with more immediate practical relevance.
Paper 1 presents an experimental realization of a room-temperature, highly scalable quantum battery, which represents a fundamental breakthrough bridging macroscopic quantum energy storage and thermodynamics. While Paper 2 offers a valuable algorithmic tool for optimizing existing photonic entanglement experiments, Paper 1 introduces a novel, paradigm-shifting physical platform for a highly anticipated quantum technology, offering greater long-term innovation and broader conceptual impact across quantum physics and energy sciences.
Paper 2 likely has higher impact: it experimentally realizes a room-temperature, macroscopic quantum battery platform and introduces an operational, tomography-free capacity measurement with validated links to multiple entropy measures. This combines methodological rigor with broad relevance to quantum thermodynamics, quantum information, and energy/thermal physics, and is timely given interest in practical quantum technologies. Paper 1 is novel and useful for photonic experiment design, but its impact is more domain-specific (quantum optics/photonic state engineering) and primarily algorithmic/optimization-driven rather than a new scalable experimental platform.
Paper 2 likely has higher scientific impact due to strong real-world applicability and timeliness: it demonstrates a record-high secret key rate for free-space CVQKD under very high loss and turbulence, addressing key deployment bottlenecks (LLO operation, leakage noise, stability). It combines theory (protocol equivalence) with a convincing system-level implementation, making it broadly relevant to quantum communications, security, and network engineering. Paper 1 is novel and rigorous experimentally, but quantum batteries remain less mature technologically, with nearer-term impact and cross-field adoption likely smaller than deployable QKD advances.
Paper 2 likely has higher impact: it targets early fault-tolerant quantum computing with neutral atoms, a timely and central bottleneck for achieving quantum advantage. It proposes an architectural innovation (teleportation-based parallelization) with quantified spacetime speedups and detailed end-to-end compilation/scheduling simulations, directly informing hardware roadmap decisions. Its applicability spans quantum architecture, error correction, compilation, and experimental system design. Paper 1 is a strong experimental demonstration connecting quantum thermodynamics and coherence-enhanced “battery” capacity, but near-term real-world energy-storage applications are less direct and the concept is more niche compared to fault tolerance’s cross-field relevance.
Paper 2 establishes a fundamental theoretical framework connecting quantum error correction to continuous quantum environments via an exact mapping to boundary CFT and the anisotropic Kondo model. This reveals previously unknown fundamental limits of surface codes under realistic non-Markovian noise, directly impacting the viability of fault-tolerant quantum computing. The finding that long-range environments can undermine topological protection challenges core assumptions in QEC and has broad implications across quantum computing, condensed matter, and open quantum systems. Paper 1, while experimentally impressive, demonstrates a quantum battery concept with less transformative implications for the field.
Paper 1 pairs solid methodological rigor (tomography-free operational capacity measurement, controlled dephasing test, entropy–capacity relations) with a compelling experimental milestone: a room-temperature, macroscopic (≈10^12 atoms) quantum-battery platform with long coherence. Its real-world applicability and timeliness are high given interest in quantum thermodynamics and quantum technologies beyond cryogenic setups, and it can influence multiple areas (quantum energy storage, metrology, open-system thermodynamics). Paper 2 is theoretically elegant and broadly relevant to noisy many-body dynamics, but its impact is likely more specialized and less immediately translational.
Paper 1 introduces a novel exact analytical technique for matchgate circuits with Pauli noise, providing fundamental insights into how decoherence affects critical quantum states. It reveals surprising non-equilibrium physics (thermal quasi-particle distributions from infinite-temperature noise) with broad implications for quantum error correction, many-body physics, and near-term quantum experiments. Paper 2, while experimentally impressive in demonstrating a room-temperature quantum battery, represents more of an incremental advance in quantum thermodynamics on a specific platform. Paper 1's analytical framework has broader theoretical applicability and addresses the timely question of noise effects on quantum states relevant to quantum computing.
Paper 1 provides fundamental theoretical advances with broad algorithmic implications: exponentially improved effective descriptions of bosonic systems impact classical simulation, quantum learning algorithms, and complexity theory. The results apply universally to physical bosonic systems and connect to quantum computing foundations. Paper 2, while experimentally impressive as a room-temperature quantum battery demonstration, addresses a narrower application area (quantum batteries) where practical advantages over classical energy storage remain unclear, and the scalability claims need further validation.
Paper 1 likely has higher scientific impact due to an experimental realization of a room-temperature, macroscopic-scale quantum battery platform (thermal Rb vapor, ~10^12 atoms) with operational, tomography-free capacity measurement and quantified coherence/entropy–capacity relations. This combines novelty with clear real-world relevance (scalable energy storage concepts, quantum thermodynamics) and timeliness in quantum technologies. Paper 2 offers strong theoretical rigor and elegant DFS/synchronization criteria, but is more specialized and less directly translational; its broader impact is likely narrower than a validated experimental platform with operational metrics.
Paper 2 demonstrates a room-temperature quantum battery using thermal atomic vapor—a scalable, practical platform—connecting quantum coherence directly to energy storage capacity with ~10^12 atoms. This experimental realization bridges quantum thermodynamics with macroscopic energy storage, offering broader interdisciplinary impact across quantum information, thermodynamics, and potentially energy technology. Paper 1, while rigorous in its theoretical treatment of phonon lasing and sensing enhancement, is more incremental, extending existing work to single-ion configurations. Paper 2's novelty in experimentally validating quantum battery concepts at room temperature and macroscopic scale gives it higher impact potential.
Paper 1 likely has higher impact due to a timely, experimentally realized room‑temperature “quantum battery” platform with macroscopic atom numbers and long coherence, plus an operational (tomography-free) capacity definition linked to multiple entropy measures—bridging quantum thermodynamics, metrology, and scalable hardware. It offers clearer near-term experimental applicability and broad cross-field relevance. Paper 2 is methodologically solid and useful (MPS density-matrix treatment of decoherence in waveguide QED), but is more incremental/technical and primarily impacts a narrower modeling community, with less immediate headline experimental demonstration.
Paper 2 demonstrates an experimental realization of a room-temperature quantum battery using a scalable platform (~10^12 atoms), connecting quantum thermodynamics theory with practical energy storage. It introduces novel tomography-free protocols, verifies coherence-enhanced capacity, and establishes entropy-capacity relations experimentally. This has broader impact across quantum technologies, thermodynamics, and energy storage. Paper 1, while rigorous and important for foundations of quantum mechanics, establishes a no-go result that largely formalizes what was already widely accepted (Bell's theorem cannot be circumvented locally), limiting its novelty and breadth of impact.
Paper 1 demonstrates an experimental realization of a room-temperature quantum battery using a macroscopic atomic ensemble (~10^12 atoms), which is a significant milestone bridging quantum thermodynamics theory with practical implementation. It introduces a tomography-free protocol for measuring battery capacity and experimentally verifies coherence-based enhancements. This has broader impact due to its experimental nature, scalability potential, and real-world applicability. Paper 2 presents a computational framework (PINNs for QFI optimization) limited to 6 qubits with acknowledged scalability issues, making it more incremental in scope.
Paper 1 presents an experimental realization of a room-temperature quantum battery using a macroscopic number of atoms, offering high novelty and direct pathways to scalable, real-world quantum energy storage. In contrast, Paper 2 is a numerical study on state preparation complexity in Rydberg arrays, which, while valuable for quantum simulation, has a narrower immediate impact compared to the breakthrough experimental demonstration of a functional quantum battery.
Paper 2 targets a central bottleneck for a quantum internet—loss-tolerant long-distance quantum communication—and proposes concrete, performance-evaluated repeater protocols with secure key-rate calculations and an improved CBSM scheme. Its potential real-world impact is broad (QKD, networking, distributed QC) and timely given rapid experimental progress in bosonic/GKP platforms. Methodologically it appears more system-level and quantitatively benchmarked. Paper 1 is novel and experimentally strong, but quantum batteries remain less technologically mature with narrower near-term applications and likely smaller cross-field impact.
Paper 1 likely has higher impact due to stronger novelty and experimental significance: it realizes a room-temperature, macroscopic (10^12 atoms) quantum battery with long coherence, introduces an operational, tomography-free capacity measurement, and quantitatively links capacity to multiple entropy measures under controlled dephasing. This advances quantum thermodynamics and quantum technologies with a scalable physical platform. Paper 2 is timely and interdisciplinary, but largely parallels classical eigenvector centrality, with limited demonstrated biological/algorithmic advantage beyond proof-of-principle and small validation cases, which may constrain broad impact.
Paper 2 presents a groundbreaking observation of tunable superradiant frequency combs and connects it to continuous time crystals, offering profound implications for both fundamental non-equilibrium physics and practical quantum metrology. While Paper 1 is highly novel in realizing a room-temperature quantum battery, Paper 2's dual-rail frequency combs have broader, more immediate applications in quantum information processing and precision measurement, granting it a higher potential scientific impact.
Paper 2 likely has higher impact because it reports a room-temperature experimental realization of a quantum battery in a macroscopic (10^12-atom) platform, with an operational, tomography-free capacity measurement and experimentally verified links between capacity, coherence, and multiple entropy measures—results that are timely and broadly relevant to quantum thermodynamics, quantum information, and AMO physics. Paper 1 is novel and useful for fault-tolerant quantum computing with qLDPC codes, but its impact is more specialized and depends on future hardware adoption and assumptions about correlated errors.