aiqbench analysis
This study corrects the thermodynamic interpretation of apparent second-law violations in quantum Szilard engines, identifying nonorthogonal-state erasure as the true resource rather than state distinguishing. By proving that hypothetical perfect distinguishing actually increases joint entropy, the authors clarify how work extraction limits are maintained within standard quantum mechanical frameworks. This theoretical refinement is essential for understanding fundamental constraints on information-to-energy conversion in future quantum thermodynamic devices.
Nonorthogonal-state erasure as the resource behind apparent second-law violations
arXiv:2608.13881v1 Announce Type: new Abstract: Perfect deterministic distinguishing of nonorthogonal quantum states is forbidden by the linear and unitary structure of quantum mechanics. It has often been assumed that, if such distinguishing were available, it would be the resource enabling work extraction from a single heat bath. We show that this expectation identifies the wrong thermodynamic operation and prove such hypothetical operation increases, rather than decreases, the joint entropy of system and detector. The entropy-decreasing resource is instead the inverse operation, which we call nonorthogonal-state erasure. Reanalyzing a Peres-type Szilard engine, we show that the apparent extracted work $W_{\mathrm{ext}}=0.2766k_{\mathrm{B}}T$ for an equal mixture of an atomic ensemble with spin state $\left|\uparrow\right\rangle $ and $\left|\rightarrow\right\rangle $. Thus the apparent second-law violation is supplied not by nonorthogonal-state distinguishing, but by a nonorthogonal quantum state erasure.
Abstract:Perfect deterministic distinguishing of nonorthogonal quantum states is forbidden by the linear and unitary structure of quantum mechanics. It has often been assumed that, if such distinguishing were available, it would be the resource enabling work extraction from a single heat bath. We show that this expectation identifies the wrong thermodynamic operation and prove such hypothetical operation increases, rather than decreases, the joint entropy of system and detector. The entropy-decreasing resource is instead the inverse operation, which we call nonorthogonal-state erasure. Reanalyzing a Peres-type Szilard engine, we show that the apparent extracted work $W_{\mathrm{ext}}=0.2766k_{\mathrm{B}}T$ for an equal mixture of an atomic ensemble with spin state $\left|\uparrow\right\rangle $ and $\left|\rightarrow\right\rangle $. Thus the apparent second-law violation is supplied not by nonorthogonal-state distinguishing, but by a nonorthogonal quantum state erasure.
Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
arXiv:2608.13881 [quant-ph]
(or arXiv:2608.13881v1 [quant-ph] for this version)
https://doi.org/10.48550/arXiv.2608.13881 Focus to learn more arXiv-issued DOI via DataCite (pending registration)
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Full text under the publisher's open licence · 225 words
