REVIEW 4 major objections 5 minor 1 cited by
Hamiltonian $k$-Locality is the Key Resource for Powerful Quantum Battery Charging
T0 review · 4 major / 5 minor · reviewed 2026-08-10 · deepseek-v4-flash
Pith's one-line read Quantum battery charging power is bounded by Hamiltonian locality, not by entanglement: $|P(t)| \le 12gkq\|H_C\|$.
desk verdict A promising unified bound on quantum battery charging power, but the proof's hard cutoff of the AKLH tail is not an upper bound and the central claim doesn't hold as written. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the Arad-Kuwahara-Landau-Hastings (AKLH) lemma, adapted to the battery-charger setting. It bounds $\|\Pi_{[m\epsilon,(m+1)\epsilon)} h^C_X \Pi_{[m'\epsilon,(m'+1)\epsilon)}\|$, the maximum energy transition a single charger term $h^C_X$ can induce between two energy windows of the battery, by $\|h^C_X\| e^{-(\Delta E - 4A)/(2gq)}$, where $A$ is the total norm of the battery terms that fail to commute with $h^C_X$ and is at most $gk$. The proof discretizes the battery spectrum into windows of width $\epsilon$, expresses the commutator $[H_C,H_B]$ as a sum over window indices weighted by $|m-m'|\epsilon$, and then replaces the exponentially suppressed off-window matrix elements by zero beyond $|m-m'| = 4gk/\epsilon + 1$. That hard cutoff is what converts the many-body locality statement into the numerical prefactors $12gk$ and $12gkq$.
What would settle it
Compute the tail that the hard cutoff discards in the supplemental derivation by summing $|m-m'| \epsilon \, \alpha_m \alpha_{m'} \|h^C_X\| e^{-(\Delta E - 4A)/(2gq)}$ for $|m-m'| > 4gk/\epsilon + 1$ at $A = gk$ and check whether the commutator norm exceeds $12gk\|H_C\|$; or simulate a small g-extensive $q$-local battery charged by a $k$-local g-extensive all-to-all charger and measure $\max_t |P(t)|$ against $12gkq\|H_C\|$.
Extended reading notes
Core claim
This paper establishes that when the battery Hamiltonian is $q$-local (each interaction term acts on at most $q$ lattice sites) and the charger Hamiltonian is $k$-local, both satisfying the g-extensive condition (the interaction strengths incident on any single site sum to at most $g$), the instantaneous charging power obeys $|P(t)| \le 12gkq\|H_C\|$, and $|P(t)| \le 12gk\|H_C\|$ when the battery is non-interacting. The proof projects the battery spectrum into energy windows and uses the Arad-Kuwahara-Landau-Hastings (AKLH) lemma to show that a local charger term can induce transitions only across an energy range of order $4gk$, with transitions beyond that range exponentially suppressed regardless of how entangled the battery state is. The paper calls this phenomenon locality of energy: correlations do not carry energy across the lattice, which explains why charging only boundary sites leaves the bulk unchanged and why long-range all-to-all models give no power advantage once the charger energy is kept extensive. It also proves that any $k$-local g-extensive charger is energetically equivalent to a Hamiltonian built from commuting terms, so circuit-based charging can match Hamiltonian-based charging power.
Load-bearing premise
The proof replaces the AKLH lemma's exponential suppression of energy transitions by a hard cutoff, setting the charger's matrix elements to zero beyond $|m-m'| = 4gk/\epsilon + 1$; at $\Delta E = 4gk$ with $A \approx gk$ the lemma itself only suppresses by a factor of order one, so the discarded tail may contribute more than the claimed $12gk$ constant.
Editorial extensions
If this is right
- Entanglement is demoted from a resource to a by-product: the bound contains no entanglement measure, and charging power is governed by $k$, $q$, and $g$.
- Because both $k$ and $q$ enter the bound multiplicatively, optimizing the battery and charger together gives an enhancement that tuning only one side cannot.
- Long-range all-to-all charger models, once normalized to be g-extensive, lose their apparent power advantage: the participation number drops out of the upper bound.
- Every $k$-local g-extensive charging Hamiltonian is energetically equivalent to a commuting Hamiltonian, so unitary circuit-based chargers achieve the same maximum power as Hamiltonian-based chargers.
- The per-cell energy capacity $g$ is a controlling parameter, so cells with large local energy capacity, such as bosonic modes, are a natural route to higher charging power.
Reading between the lines
- The constant 12 in $12gkq$ is probably not tight. At transition energy $\Delta E = 4gk$ with $A \approx gk$, the AKLH exponential factor is of order one, so a sharper treatment of the discarded tail could change the prefactor while preserving the $gkq$ scaling.
- The bound implies a minimal charging-time scale of order $\Delta E/(12gkq\|H_C\|)$; comparing this with standard quantum speed limits could connect battery charging to the broader problem of minimum time for state transformation.
- One could test locality of energy directly in a spin chain or Rydberg array by charging only boundary sites and monitoring bulk energy and entanglement separately: the paper predicts the bulk remains energetically cold even while entanglement grows.
- The same commutator argument should bound discharging and work-extraction power, since it relies only on $[H_C,H_B]$ and the g-extensive structure rather than on the direction of energy flow.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims to identify Hamiltonian k-locality and the g-extensive energy condition as the key resources for quantum battery charging power, rather than entanglement. It states two main propositions: Proposition 1 bounds instantaneous charging power by 12gk||H_C|| for a non-interacting battery charged by a k-local g-extensive charger; Proposition 2 extends this to 12gkq||H_C|| when both battery and charger are interacting, q-local and k-local and g-extensive. The main text gives formal statements and heuristic arguments, while the Supplemental Material contains the derivations: a power bound via |P(t)| ≤ ||[H_C,H_B]||, discretization of the battery energy, use of the AKLH lemma to bound off-diagonal matrix elements, a hard-cutoff approximation at energy difference 4gk, and a construction of a commuting Hamiltonian that replaces the original charger (and battery) with an energetically equivalent one. The paper also discusses implications: entanglement is not a key resource, locality of energy, and design principles for high-power chargers.
Significance. If the bound in Proposition 2 were rigorously established, the result would be significant: it would provide a general locality-based upper bound on quantum battery charging power that depends on system size only through the norms of the Hamiltonians, and it would clarify the role of entanglement versus locality. The paper also gives a falsifiable prediction that all-to-all long-range models with extensive energy should not show the extensive power advantage previously claimed, and it claims a constructive equivalence between arbitrary g-extensive k-local Hamiltonians and commuting-term circuits. These are valuable research directions. However, the significance is currently conditional because the central proof step in the Supplemental Material is not valid as written and the factor q in Proposition 2 is asserted without a detailed derivation.
major comments (4)
- [Supplemental Material, 'Bounding the power using AKLH lemma', Eqs. (9)-(14)] The derivation of the hard cutoff is not an upper bound. The text sets H_C_{m,m'} = 0 for |m-m'| > 4gk/epsilon + 1, based on the AKLH bound e^{-(Delta E - 4A)/(2gq)}. But the lemma gives an exponential upper bound, not a hard cutoff: at Delta E = 4gk with A close to gk, the exponential factor is O(1), so the omitted tail is not negligible. Summing the tail over all |m-m'| beyond the cutoff can contribute a term of order ||H_C||(2gq + g q^2/k) when epsilon is chosen near 4gk, which can exceed the claimed 12gk||H_C|| constant for q of order k^2 or larger. Since Proposition 1 relies on this cutoff, the bound 12gk||H_C|| is not established by the provided argument.
- [Proposition 2 and Supplemental Material, 'Interacting battery and Interacting charger'] The proof of Proposition 2 is not provided in detail. The text states that any q-local g-extensive battery Hamiltonian can be decomposed as a sum of 1/\bar q commuting q-local gq-extensive terms, with H_B = (1/\bar q) \sum_p \bar H^B_p, and then applies the Proposition 1 bound to each commutator [H_C, \bar H^B_p] to obtain 1/\bar q \sum_p 12gk(??) ||H_C||. The factor q in the final 12gkq appears to be inserted by hand; the preceding inequality in the Supplemental Material simply writes 12gkq without showing how the q emerges from the sum over p or how the locality and extensivity parameters of the \bar H^B_p enter. The derivation of the bound for a single q-local battery term also inherits the invalid cutoff from the first major comment. Thus the central claim of Proposition 2 is not rigorously supported.
- [Supplemental Material, construction of commuting Hamiltonian, paragraph 'Using the same construction...'] The claim that any k-local g-extensive Hamiltonian can be replaced by an energetically equivalent Hamiltonian composed of commuting terms, with error O(epsilon N), is not proven. The construction is illustrated for a specific 2-local Hamiltonian, and the general statement is asserted with reference to a previous work. The error bound O(epsilon N) is stated without derivation, and it is unclear how this replacement preserves the charging power bound for all states and times, especially because the equivalence is only approximate and the paper's propositions require exact upper bounds. This is a load-bearing step for the claimed equivalence between unitary-circuit and Hamiltonian-based charging protocols, but it is not established in the present manuscript.
- [Main text, Lemma 1 and Eq. (7)] Lemma 1 states ||Π h^C_X Π|| ≤ ||h^C_X|| e^{-(1/(2gq))[(m-m')epsilon - epsilon - 4A]} with A defined as the sum of norms of battery terms non-commuting with h^C_X. The example in Eq. (7) substitutes A = O(g) and arrives at an exponent with denominator 4g, but the exponent's derivation is not shown in detail. More importantly, the lemma as stated in the main text is taken from the AKLH lemma, and the proof in the Supplemental Material has the same issue as the hard cutoff: the bound is only valid when the minimizer p is positive, which requires Delta E > 2A; the formula is then written with a compact logarithm inequality that may not hold for all Delta E. The presentation is therefore not self-contained and the conditions under which the lemma applies are not precisely stated.
minor comments (5)
- [Abstract and Introduction] The abstract contains an ungrammatical sentence: 'To derive this new bound, we have also addressed several open questions previously noted in the literature but lacks an explanation.' The intended meaning is clear, but the sentence should be rewritten.
- [Main text, Eq. (4)] The inequality in Eq. (4) has a typo: the subscript in one projector is written as 'j epsilon' instead of 'm epsilon'. The expression '||Π[mϵ,jϵ+ϵ)h^C_X Π[m'ϵ,m'ϵ+ϵ)||' should read '||Π[mϵ,mϵ+ϵ)h^C_X Π[m'ϵ,m'ϵ+ϵ)||'.
- [Main text, Proposition 1 and Proposition 2 statements] The factor 12 in 12gk||H_C|| and 12gkq||H_C|| is not explained in the main text; it is obtained only through a specific choice of epsilon in the Supplemental Material. The reader is not told whether the constant is optimal or whether a different epsilon could give a different prefactor.
- [Supplemental Material, definition of \bar h^C_X] The formula '\bar h^C_X = epsilon h^C_X / ||h^C_X||' is written without the norm bars in the denominator rendered clearly, and the text immediately switches to an example without defining what 'epsilon' is in that context (presumably the same epsilon used in the energy discretization). This is confusing and should be clarified.
- [References] Some references are incomplete or informal: [35] is 'In preparation (2025)', and [48] is 'See Supplemental Material', which is acceptable for a letter but should be clearly cited in the final version.
Circularity Check
No significant circularity: the central charging-power bound is derived from an external lemma and the paper's own Supplemental proof, with no fitted input renamed as a prediction.
full rationale
Score 0. The derivation chain is not circular. The central bound |P(t)| ≤ 12gkq||H_C|| is obtained from the operator-norm identity |P(t)| ≤ ||[H_C,H_B]||, the external Arad-Kuwahara-Landau-Hastings lemma [40], and a discretization argument in the Supplemental Material. The g-extensive condition and the k/q-locality assumptions are modeling assumptions, not fitted parameters; no quantity in the bound is fit to data or to the target result. The paper's self-citations are not load-bearing: [35] is motivational context about numerical investigations, and [48] is the paper's own Supplemental Material whose proof is reproduced in the text and rests on the external AKLH lemma plus elementary norm estimates. The commuting-Hamiltonian construction used for Proposition 2 is based on an external result [36] and on the same AKLH bound; it does not assume Proposition 2 as an input. The reader's objection about replacing the AKLH exponential tail by a hard cutoff at |m-m'| = 4gk/ε + 1 is a potential mathematical flaw in the proof, because the discarded tail need not be negligible and may contribute terms exceeding the claimed constant. However, that is a correctness and rigor concern, not circularity: the flawed step does not make the conclusion equivalent to an input by construction, nor does it rename a fitted parameter as a prediction. Therefore no circular step is present.
Assumptions & free parameters
assumptions (4)
- domain assumption The Arad-Kuwahara-Landau-Hastings (AKLH) lemma holds for g-extensive q-local battery Hamiltonians and bounds the matrix elements of local charger terms between energy windows.
- domain assumption Both battery and charger Hamiltonians satisfy the g-extensive condition (Eq. 2), meaning the sum of norms of terms touching any site is at most g.
- ad hoc to paper Exponential suppression of off-diagonal matrix elements of the charger can be replaced by a hard cutoff at an energy difference 4gk.
- ad hoc to paper Any k-local, g-extensive Hamiltonian can be replaced by an energetically equivalent Hamiltonian composed of commuting terms, with error O(ϵN), and this replacement preserves the power bound.
Cite this review
Pith. "Pith review of Hamiltonian $k$-Locality is the Key Resource for Powerful Quantum Battery Charging." pith.science (2026). https://pith.science/paper/XXTSKKDV
@misc{pith2026250112000,
author = {Pith},
title = {Pith review of: Hamiltonian $k$-Locality is the Key Resource for Powerful Quantum Battery Charging},
year = {2026},
howpublished = {\url{https://pith.science/paper/XXTSKKDV}},
note = {Machine review of arXiv:2501.12000}
}
read the original abstract
Storing and extracting energy using quantum degrees of freedom is a promising approach to leveraging quantum effects in energy science. Early experimental efforts have already demonstrated its potential to surpass the charging power of existing technologies. In this context, it is crucial to identify the specific quantum effects that can be exploited to design the most efficient quantum batteries and push their performance to the ultimate limit. While entanglement has often been considered a key factor in enhancing charging (or discharging) power, our findings reveal that it is not as critical as previously thought. Instead, three parameters emerge as the most significant in determining the upper bound of instantaneous charging power: the locality of the battery and charger Hamiltonians, and the maximum energy storable in a single unit cell of the battery. To derive this new bound, we have also addressed several open questions previously noted in the literature but lacks an explanation. This bound provides a foundation for designing the most powerful charger-battery systems, where combined optimization of both components offers enhancements that cannot be achieved by manipulating only one of them.
Figures
Forward citations
Cited by 1 Pith paper
-
Floquet driven long-range interactions induce super-extensive scaling in quantum batteries
Floquet-driven long-range interacting spin chains can charge quantum batteries with power scaling super-linearly with system size, but only for moderate sizes and in specific parameter regimes, as shown by an upper-bo...
Reference graph
Works this paper leans on
-
[1]
S. Carnot, R´ eflexions sur la puissance motrice du feu et sur les machines propres ` a d´ evelopper cette puissance, Bachelier, Paris, 1824
-
[2]
D. Bluvstein, A. Omran, H. Levine, A. Keesling, G. Se- meghini, S. Ebadi, T. T. Wang, A. A. Michailidis, N. Maskara, W. W. Ho, S. Choi, M. Serbyn, M. Greiner, V. Vuli´ c, M. D. Lukin, Science371, 6536, 1355–1359 (2021)
work page 2021
-
[3]
A. J. Daley, I. Bloch, C. Kokail, S. Flannigan, N. Pearson, M. Troyer, P. Zoller, Nature 607, 7920, 667–676 (2022)
work page 2022
-
[4]
R. Alicki and M. Fannes, Physical Review E—Statistical, Nonlinear, and Soft Matter Physics 87, 4, 042123 (2013)
work page 2013
-
[5]
F. Campaioli, S. Gherardini, J. Q. Quach, M. Polini, G. M. Andolina, Reviews of Modern Physics 96, 3, 031001 (2024)
work page 2024
-
[6]
J. Q. Quach, G. Cerullo, T. Virgili, Joule 7, 10, 2195– 2200 (2023)
work page 2023
-
[7]
T. Kim, W. Song, D. Y. Son, L. K. Ono, Y. Qi, Journal of Materials Chemistry A 7, 7, 2942–2964 (2019)
work page 2019
-
[8]
S. Gherardini, F. Campaioli, F. Caruso, F. C. Binder, Physical Review Research 2, 1, 013095 (2020)
work page 2020
Show all 62 references
-
[9]
J. Q. Quach and W. J. Munro, Physical Review Applied 14, 2, 024092 (2020)
2020
-
[10]
Castellano, D
R. Castellano, D. Farina, V. Giovannetti, A. Acin, Phys- ical Review Letters 133, 15, 150402 (2024)
2024
-
[11]
Francica, F
G. Francica, F. C. Binder, G. Guarnieri, M. T. Mitchison, J. Goold, F. Plastina, Physical Review Letters 125, 18, 180603 (2020)
2020
-
[12]
H. L. Shi, S. Ding, Q. K. Wan, X. H. Wang, W. L. Yang, Physical Review Letters 129, 13, 130602 (2022)
2022
-
[13]
Crescente, M
A. Crescente, M. Carrega, M. Sassetti, D. Ferraro, New Journal of Physics 22, 6, 063057 (2020)
2020
-
[14]
L. P. Garc ´ ıa-Pintos, A. Hamma, A. Del Campo, Physical Review Letters 125, 4, 040601 (2020)
2020
-
[15]
Bakhshinezhad, B
P. Bakhshinezhad, B. R. Jablonski, F. C. Binder, N. Friis, Physical Review E 109, 1, 014131 (2024)
2024
-
[16]
J. Q. Quach, K. E. McGhee, L. Ganzer, D. M. Rouse, B. W. Lovett, E. M. Gauger, T. Virgili, Science Advances 8, 2, eabk3160 (2022)
2022
-
[17]
Metzler, J
F. Metzler, J. I. Sandoval, N. Galvanetto, Journal of Physics: Energy 5, 4, 041001 (2023)
2023
-
[18]
Campaioli, F
F. Campaioli, F. A. Pollock, F. C. Binder, L. C´ eleri, J. Goold, S. Vinjanampathy, and K. Modi, Physical Re- view Letters 118, 15, 150601 (2017)
2017
-
[19]
F. C. Binder, S. Vinjanampathy, K. Modi, and J. Goold, New Journal of Physics 17, 7, 075015 (2015)
2015
-
[20]
T. P. Le, J. Levinsen, K. Modi, M. M. Parish, and F. A. Pollock, Physical Review A 97, 2, 022106 (2018)
2018
-
[21]
F. Q. Dou, Y. Q. Lu, Y. J. Wang, and J. A. Sun, Physical Review B 105, 11, 115405 (2022)
2022
-
[22]
X. L. Zhang, X. K. Song, and D. Wang, Advanced Quan- tum Technologies 7, 9, 2400114 (2024)
2024
-
[23]
Ghosh, T
S. Ghosh, T. Chanda, and A. Sen, Physical Review A 101, 3, 032115 (2020)
2020
-
[24]
F. Zhao, F. Q. Dou, and Q. Zhao, Physical Review A 103, 3, 033715 (2021)
2021
-
[25]
Rossini, G
D. Rossini, G. M. Andolina, D. Rosa, M. Carrega, and M. Polini, Physical Review Letters 125, 23, 236402 (2020)
2020
-
[26]
Ferraro, M
D. Ferraro, M. Campisi, G. M. Andolina, V. Pellegrini, and M. Polini, Physical Review Letters 120, 11, 117702 (2018)
2018
-
[27]
A. G. Catalano, S. M. Giampaolo, O. Morsch, V. Gio- vannetti, and F. Franchini, PRX Quantum 5, 3, 030319 (2024)
2024
-
[28]
Juli` a-Farr´ e, T
S. Juli` a-Farr´ e, T. Salamon, A. Riera, M. N. Bera, and M. Lewenstein, Physical Review Research 2, 2, 023113 (2020)
2020
-
[29]
G. M. Andolina, M. Keck, A. Mari, M. Campisi, V. Gio- vannetti, and M. Polini, Physical Review Letters 122, 4, 047702 (2019)
2019
-
[30]
G. M. Andolina, M. Keck, A. Mari, V. Giovannetti, and M. Polini, Physical Review B 99, 20, 205437 (2019)
2019
-
[31]
F. H. Kamin, F. T. Tabesh, S. Salimi, and A. C. Santos, Physical Review E 102, 5, 052109 (2020)
2020
-
[32]
Zhang and M
X. Zhang and M. Blaauboer, Frontiers in Physics 10, 1097564 (2023)
2023
-
[33]
J. Y. Gyhm and U. R. Fischer, A VS Quantum Science 6, 1, 015901 (2024)
2024
-
[34]
J. Y. Gyhm, D. ˇSafr´ anek, and D. Rosa, Physical Review Letters 128, 14, 140501 (2022)
2022
-
[35]
Sarkar, R
A. Sarkar, R. K. Shukla, S. Ghosh, In preparation (2025)
2025
-
[36]
Kuwahara, New Journal of Physics 18, 5, 053034 (2016)
T. Kuwahara, New Journal of Physics 18, 5, 053034 (2016)
2016
-
[37]
C. F. Chen and A. Lucas, Physical Review Letters 123, 25, 250605 (2019)
2019
-
[38]
Kuwahara and K
T. Kuwahara and K. Saito, Physical Review X 10, 3, 6 031010 (2020)
2020
-
[39]
M. C. Tran, C. F. Chen, A. Ehrenberg, A. Y. Guo, A. Deshpande, Y. Hong, and A. Lucas, Physical Review X 10, 3, 031009 (2020)
2020
-
[40]
I. Arad, T. Kuwahara, and Z. Landau, Journal of Statisti- cal Mechanics: Theory and Experiment 2016, 3, 033301 (2016)
2016
-
[41]
Ghosh and A
S. Ghosh and A. Sen, Physical Review A 105, 2, 022628 (2022)
2022
-
[42]
Goldhirsch, E
I. Goldhirsch, E. Levich, and V. Yakhot, Physical Review B 19, 9, 4780 (1979)
1979
-
[43]
M. B. Hastings, Quantum Theory from Small to Large Scales, Oxford Scholarship Online, 95, 171–212 (2010)
2010
-
[44]
Bukov, D
M. Bukov, D. Sels, and A. Polkovnikov, Physical Review X 9, 1, 011034 (2019)
2019
-
[45]
M. R. Lam, N. Peter, T. Groh, W. Alt, C. Robens, D. Meschede, and A. Alberti, Physical Review X 11, 1, 011035 (2021)
2021
-
[46]
C. F. A. Chen, A. Lucas, and C. Yin, Reports on Progress in Physics 86, 11, 116001 (2023)
2023
-
[47]
E. H. Lieb and D. W. Robinson, Communications in Mathematical Physics 28, 3, 251–257 (1972)
1972
-
[48]
See Supplemental Material
-
[49]
J. P. Keating, N. Linden, and H. J. Wells, Communica- tions in Mathematical Physics 338, 81–102 (2015)
2015
-
[50]
Kim and D
H. Kim and D. A. Huse, Physical Review Letters 111, 12, 127205 (2013)
2013
-
[51]
G. M. Andolina, V. Stanzione, V. Giovannetti, and M. Polini, arXiv preprint arXiv:2409.08627 (2024)
2024 arXiv
-
[52]
Kuwahara, I
T. Kuwahara, I. Arad, L. Amico, and V. Vedral, Quan- tum Science and Technology 2, 1, 015005 (2017)
2017
-
[53]
M. C. Ba˜ nuls, D. A. Huse, and J. I. Cirac, Physical Re- view B 101, 14, 144305 (2020)
2020
-
[54]
Kuwahara, Journal of Statistical Mechanics: Theory and Experiment 2016, 5, 053103 (2016)
T. Kuwahara, Journal of Statistical Mechanics: Theory and Experiment 2016, 5, 053103 (2016)
2016
-
[55]
K. S. Rai, J. I. Cirac, and ´A. M. Alhambra, Quantum 8, 1401 (2024)
2024
-
[56]
Anshu, New Journal of Physics 18, 8, 083011 (2016)
A. Anshu, New Journal of Physics 18, 8, 083011 (2016)
2016
-
[57]
Lloyd, Physical Review A 61, 1, 010301 (1999)
S. Lloyd, Physical Review A 61, 1, 010301 (1999)
1999
-
[58]
K. V. Hovhannisyan, M. Perarnau-Llobet, M. Huber, and A. Ac ´ ın, Physical Review Letters111, 24, 240401 (2013) . SUPPLEMENT AL MA TERIAL Bounding Charging power using operator norm The average energy of the battery at time t is given by ⟨EB⟩t = ⟨ψ(t)| H B |ψ(t)⟩ . The time ev...
2013
-
[59]
Now it has three parts, −g12(σz 1σz 2), −g12α(σx 1 σx 2 ) and −g12α(σy 1 σy 2 )
So our newly constructed Hamiltonian would be of the form, ¯H C = S1 ϵ (σα 1 σα 2 ) + S2 ϵ σβ 2 + S3 ϵ (σα 3 σα 4 ) + S4 ϵ σβ 4 + · · ·+ SN −1 ϵ (σα N −1σα N ) + SN ϵ σβ N 14 The only non-commuting part which still remains is in the term ( σα 1 σα 2 ). Now it has three parts, ...
-
[60]
+ |α|S1 3ϵ (σx 1 σx 2 ) + |α|S1 3ϵ (σy 1 σy 2 ) + S2 ϵ σz 2 + S3 3ϵ (σz 3σz
-
[61]
+ |α|S3 3ϵ (σx 3 σx 4 ) + |α|S3 3ϵ (σy 3 σy 4 ) + S4 ϵ σz 4 + · · ·+ SN −1 3ϵ (σz N −1σz N ) + |α|SN −1 3ϵ (σx N −1σx N ) + |α|SN −1 3ϵ (σy N −1σy N ) + SN ϵ σz N Now we can write it as, ¯H C = S1 3ϵ (σz 1σz
-
[62]
+ · · ·+ SN −1 3ϵ (σz N −1σz N ) | {z } ¯H C 1 + |α|S1 3ϵ (σx 1 σx 2 ) + |α|S3 3ϵ (σx 3 σx 4 ) + · · ·+ |α|SN −1 3ϵ (σx N −1σx N ) | {z } ¯H C 2 + |α|S1 3ϵ (σy 1 ⊗σy 2 ) + |α|S3 3ϵ (σy 3 ⊗σy 4 ) + · · ·+ |α|SN −1 3ϵ (σy N −1σy N ) | {z } ¯H C 3 + S2 ϵ σz 2 + S4 ϵ σz 4 + · · ·+...
Reviewed August 10, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.