{"id":"ed05fd69-eebb-4e6d-a6a2-15e0fb5d47e1","arxiv_id":"2508.14857","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Introduces single-click and double-single-click remote state preparation protocols for weak coherent pulse clients that achieve higher rates than the double-click protocol at comparable fidelity.","lead":"Remote state preparation lets a simple client prepare a chosen quantum state on a server using shared entanglement. This paper adds two speed-optimized variants for weak-coherent-pulse clients and shows they can beat the standard double-click protocol in rate without giving up fidelity.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"SC rate advantage over DC is contingent on phase-stabilization feasibility; paper leaves σ_SC as a free parameter and does not benchmark it against demonstrated phase synchronization, so the 'consistent' advantage claim is not grounded for high-fidelity targets.","rationale":"The reader's weakest_assumption correctly identifies the phase-stabilization requirement as the main threat to the SC-vs-DC advantage. My own analysis confirms that the paper's rate and fidelity formulas are internally consistent: re-deriving the leading-order expansions from Appendix A reproduces Eqs. (5) and (1), and the rate ratio R_SC/R_DC = 4/η_s > 1 for all η_s ≤ 1. The phase-noise model is also self-consistent, but it caps the achievable fidelity at (1+e^{-σ²/2})/2. Since the paper does not provide an experimental benchmark for σ_SC, the headline claim of a 'consistent' advantage is not fully supported. This does not invalidate the protocol proposal; it means the acceptance should remain conditional on phase-stabilization feasibility, exactly as the reader concluded. No new objection beyond the reader's weakest assumption was found, so the verdict is unchanged.","tokens_in":20207,"tokens_out":37236,"duration_ms":394179,"concrete_test":"Compute the maximum tolerable σ_SC for a target fidelity F via σ_max = sqrt(-2 ln(2F-1)). For F=0.99, σ_max≈0.20 rad. Then extract the residual phase error from the phase-synchronization demonstration in Ref. [34] (or another deployed-fiber synchronization experiment) and compare. If the demonstrated σ_SC exceeds σ_max, SC cannot reach that fidelity and the rate comparison at that fidelity is vacuous. Additionally, recompute the SC and DC rate-fidelity curves including the time overhead of stabilization pulses (e.g., one pilot pulse per attempt) to see whether the rate advantage persists.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that SC achieves higher rates than DC at equal fidelity is valid only in the idealized zero-phase-noise limit. Under the paper's own phase-noise model (Section II E), the maximum attainable SC fidelity is (1+e^{-σ_SC^2/2})/2. For any target fidelity above this bound, SC cannot succeed at all, and DC remains the only option. The paper treats σ_SC as a tunable parameter and does not establish that practical active phase stabilization can keep σ_SC small enough for the fidelities relevant to QKD/BQC (typically >0.99). For F=0.99, the bound requires σ_SC ≲ 0.20 rad. The cited experimental phase synchronization work (Ref. [34]) is not used to estimate an achievable σ_SC, nor is the overhead of stabilization (e.g., pilot pulses) included in the rate comparison. Thus the abstract's claim that 'SC consistently achieves higher rates than DC' is overstated without an explicit regime of validity in terms of σ_SC.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper considers remote state preparation (RSP) with a client that uses weak coherent pulses (WCPs). It introduces two protocols—single-click (SC) and double-single-click (DSC)—and compares them with the previously known double-click (DC) protocol. The authors derive analytical expressions for the success rate and fidelity of all three protocols under loss, optimize the server's bright-state parameter ξ, and model Gaussian phase noise. Their central finding is that, to leading order in the client mean photon number |α|², SC and DC attain the same infidelity, while SC's rate scales as 2ηc|α|² versus ηcηs|α|²/2 for DC; DSC has twice the infidelity of SC/DC but a rate of 4ηc|α|²/3. The paper also discusses phase-noise limitations, compares protocols in rate–fidelity trade-off plots, and sketches an application to QKD over repeater chains, with a reduction to the CAL19 twin-field security proof in the appendix.","tokens_in":20517,"tokens_out":14461,"duration_ms":162981,"significance":"The main insight—that replacing a double-click with a single-click RSP does not incur an inherent fidelity penalty as it does in entanglement generation—is valuable and, if correct, has practical implications for quantum network clients with WCP sources. The analytical formulas are detailed enough to be checked, and the authors are transparent about some limitations (notably that the DSC fidelity is an upper bound because memory decoherence is omitted). The paper includes explicit derivations for the SC protocol, an optimized bright-state parameter, and a phase-noise model, which are useful contributions. However, the strength of the headline claim depends on a phase-noise regime that is not quantitatively grounded, and there is an internal inconsistency in the DSC rate derivation. The QKD application is only a sketch, not a full security proof, but that is appropriately caveated.","major_comments":[{"comment":"The claim that “SC consistently achieves higher rates than DC” is not valid for all target fidelities. Under the paper's own phase-noise model, the maximum SC fidelity is (1+e^{-σ_SC²/2})/2, so for F=0.99 one needs σ_SC≲0.20 rad. The paper uses σ_SC=0.5 rad in Fig. 2(b) and treats σ_SC as a free parameter without deriving an achievable value from Ref. [34]. Please state the residual phase noise demonstrated by Ref. [34], or explicitly qualify the abstract and Section III conclusions with the regime σ_SC below the threshold needed for the target fidelity.","section":"Section II E and Abstract"},{"comment":"The DSC rate derivation is internally inconsistent. Eq. (A17) defines p_SC as the single-click success probability with displacement α/√2, giving p_SC ≈ ηc|α|². Then RDSCτ ≈ (2/3)ηc|α|² P_CNOT, which cannot reproduce the leading-order 4/3 ηc|α|² in Eq. (8) for any P_CNOT ≤ 1. To match Eq. (8), p_SC must be the full-displacement success probability ≈2ηc|α|² and P_CNOT≈1. Either Eq. (A17) or Eq. (8) is wrong; please reconcile and correct the derivation.","section":"Appendix A 3, Eq. (A17) vs Eq. (8)"},{"comment":"The DSC protocol's fidelity is explicitly an upper bound because memory decoherence between the two SC successes is neglected. However, the protocol-comparison plots and the conclusion that “DSC can also achieve higher rates than DC” use this upper bound. Since the waiting time between two successes can be long, decoherence may substantially reduce the actual DSC fidelity, potentially eliminating the claimed advantage in realistic regimes. Please either include a simple decoherence model (e.g., exponential fidelity decay with waiting time) or clearly restrict the DSC claims to the ideal-memory limit and state that the comparison is against an upper bound.","section":"Section II D and Section III"}],"minor_comments":[{"comment":"The sentence “the fidelity of DC has twice the negative slope of SC in the small |α|² limit” contradicts Eqs. (1) and (5), which have the same leading coefficient ηc(4−3ηs)/(16ηs), and also contradicts Section III. Please correct this sentence.","section":"Section II C"},{"comment":"The post-selection condition after the CNOT in DSC is stated as measuring the target qubit in |0⟩ in the main text, but Appendix A 3 says the state is accepted only if the target qubit is in the bright state |1⟩. Please clarify which outcome is post-selected and ensure the derivation matches.","section":"Section II D and Appendix A 3"},{"comment":"The sentence “first order contributions in |α|² are … ηc(4−3ηs)|α|/16ηs” should read |α|², not |α|. There are also formatting issues in Eqs. (1) and (7) where division slashes are missing in the displayed formulas.","section":"Section III"},{"comment":"There is a typo: “beam splitter transformations transformations” should be “beam splitter transformations.” Other minor typos include “on;y” (Section III) and “boarder” (Section III) instead of “border.”","section":"Section II A"},{"comment":"The QKD security reduction is a sketch, not a full proof. The appendix states that “a comparison of the performance of both protocols in noisy scenarios is left for future work.” Please make clear in the main text that the QKD claim is a compatibility argument, not a security proof with finite-key analysis.","section":"Appendix C"}],"recommendation":"major_revision","confidential_remarks":"The scientific core—the SC/DC rate-fidelity comparison—appears sound and internally consistent after checking the leading-order expansions. The main issues are (i) the phase-noise regime of validity for the headline claim, (ii) a concrete inconsistency between Eq. (A17) and Eq. (8) in the DSC rate derivation, and (iii) the use of an upper-bound DSC fidelity in protocol comparison. These are fixable within the manuscript's scope, so I recommend major revision rather than rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague, read this. It is a genuinely useful protocol paper. The new thing: single-click RSP with a WCP client, plus the double-single-click variant that uses a CNOT to cancel the pulse phase. The analytics are derived from coherent-state inputs, loss channels, beamsplitters, and detector projectors—not fitted—and the leading-order infidelity and rate expressions check against each other. The central result, that SC reaches the same leading-order fidelity as DC while gaining a rate factor of about 4/η_s, survives contact with the equations. That is a real result and worth citing.\n\nThe load-bearing caveat is the paper's own phase-noise model. SC's maximum fidelity is (1+e^{-σ^2/2})/2, and σ_SC is left as a free parameter. For a target fidelity of 0.98–0.99 you need σ below roughly 0.2 rad. The authors reference the Stolk et al. phase-synchronization work but do not translate it into an achievable σ_SC, nor do they include stabilization overhead (pilot pulses, reduced duty cycle) in the rate comparison. So the abstract's claim that SC \"consistently achieves higher rates than DC\" is only true in the low-noise regime. The regime maps in Figure 4 are more honest: DC wins when σ_SC is large. The technical content is sound, but the abstract lags behind it.\n\nThe DSC idea is clever and clearly explained. However, its fidelity is explicitly an upper bound because memory decoherence between the two clicks is omitted. The authors flag this, so it is not a hidden flaw, but the practical value of DSC depends on click intervals shorter than both the phase drift and the memory coherence time, and neither is modeled. The QKD appendix is a purified, lossless, perfect-detector sketch; it shows compatibility with CAL19-style security but is not a security proof. The BQC security gap is openly acknowledged. Fine as future work, but it should not be mistaken for a completed result.\n\nMy main revision asks: state the σ regime for SC's advantage in the abstract; benchmark σ_SC against the cited phase-synchronization experiment and include stabilization overhead in the rate; and either add a decoherence model for DSC or keep the upper-bound label prominent throughout. The derivation work is solid enough that a serious referee should engage with it. I would send it to peer review.","headline":"Useful protocol paper with real analytic results; abstract overstates SC's regime of validity until phase noise is accounted for.","tokens_in":20961,"tokens_out":1722,"would_cite":true,"duration_ms":22227,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"This paper shows that remote state preparation with weak coherent pulses can use a single-click protocol that matches double-click fidelity while achieving a higher rate, plus a two-click variant that relaxes phase-stabilization demands.","keywords":["remote state preparation","weak coherent pulses","single-click protocol","double-click protocol","quantum repeaters","phase noise","measurement-device-independent QKD","blind quantum computing"],"falsifier":"On a fixed link with known client and server efficiencies and active phase stabilization, measure the accepted-state rate and fidelity of SC and DC as the client intensity is varied. The central claim fails if DC produces more accepted states per unit time than SC at the same fidelity (for example at F=0.98), or if the measured SC infidelity grows faster than ηc(4−3ηs)/(16ηs)|α|² in the small-|α|² regime, since that would indicate the leading-order error model is missing a contribution.","tokens_in":20159,"feed_emoji":"⚛️","tokens_out":9874,"duration_ms":112193,"temperature":0.7,"pith_summary":"Remote state preparation allows a low-resource client to place a known quantum state on a server's qubit using entanglement. This paper claims that when the client uses weak coherent pulses instead of true single photons, a single-click protocol—where only one photon must reach the intermediate Bell measurement—prepares the target state at the same leading-order fidelity as the standard double-click protocol while achieving a higher success rate. It also proposes a double-single-click variant that repeats the single-click step twice and applies a controlled-NOT gate, exchanging some fidelity for reduced phase-stabilization requirements. If right, these protocols let quantum-network clients trade hardware simplicity for speed without the fidelity penalty that single-click schemes pay in ordinary entanglement generation.","feed_headline":"Single-click RSP wins on rate without losing fidelity","feed_subtitle":"Weak-coherent-pulse clients can prepare states faster, and a variant skips active phase stabilization.","key_machinery":"The object that carries the argument is the click pattern at the Bell state measurement and the encoding that produces it. DC uses a two-mode encoding (polarization or time-bin) and needs a click in both modes; SC uses presence-absence encoding in a single mode, so one click on either output detector of a 50:50 beamsplitter heralds success, and the balance between client and server photon arrival probabilities is set by the server's bright-state parameter ξ. DSC repeats the SC round twice and applies a CNOT gate followed by a measurement, so the final phase is the difference of the two single-click phases, deleting any common phase drift. The phase-noise model then enters as a Gaussian σ wit","core_discovery":"The central claim is that single-click RSP is not merely faster than double-click RSP—it matches its fidelity to leading order. For a client amplitude α, client channel efficiency ηc, and server emission efficiency ηs, the SC and DC infidelities in the small-intensity limit are both ηc(4−3ηs)/(16ηs)|α|², while the dimensionless rates scale as 2ηc|α|² (SC) versus ηcηs|α|²/2 (DC), so SC strictly dominates DC whenever its phase noise is low enough to reach the target fidelity. DSC, which runs SC twice and then applies a CNOT gate, has twice the leading-order infidelity of SC/DC but still outperforms DC in rate, and it cancels the random overall phase so that only phase drift between the two cli","pith_inferences":["The paper restricts attention to equatorial states; adjusting the client intensity and the server bright-state parameter should extend SC to arbitrary latitudes without changing the single-click mechanism, giving a direct experimental handle the authors chose not to explore.","A simple pre-screening rule follows from the phase-noise ceiling: if an interferometric measurement of the client's phase shows σ above about 0.5 rad, SC cannot supply 0.98-fidelity states and the comparison should be made against DC at lower fidelity targets.","End-to-end repeater performance is not quantified here; one obvious next calculation is to include memory cutoff times and decoherence between the two DSC clicks, which the paper explicitly flags as an upper-bound assumption."],"forward_implications":["With active phase stabilization, SC supplies more remote-state-preparation successes per unit time than DC at the same target fidelity, which directly increases the rate of protocols built on RSP.","DSC removes the need for an active phase-stabilization servo when two SC successes occur within the phase-coherence time, and still beats DC's rate in some regimes.","In a repeater-chain QKD setting, the SC-based variant is equivalent to a twin-field-type protocol in the noiseless limit and can be analyzed with existing measurement-device-independent security proofs.","For applications needing several remotely prepared qubits, the higher rate of SC/DSC can beat DC on overall fidelity because slower preparation gives memory decoherence more time to act.","A composable security proof for blind quantum computing with SC is still missing; DSC may be easier to prove secure because its final phase is a phase difference, so phase randomization of both pulses is compatible."],"supporting_citations":[{"why":"Supplies the prior double-click RSP protocol with a weak coherent pulse client that SC and DSC are measured against.","marker":"[28]"},{"why":"Introduces the single-click presence-absence scheme that the SC RSP protocol adapts from entanglement generation.","marker":"[26]"},{"why":"Demonstrates single-click remote entanglement with matter qubits, grounding the SC technique experimentally.","marker":"[27]"},{"why":"Provides the active phase-synchronization method and the 0.5-rad noise value used to model SC phase noise.","marker":"[34]"},{"why":"Gives the linewidth-dependent phase-drift relation used to estimate DSC phase noise between consecutive clicks.","marker":"[35]"},{"why":"Supplies the server photon-emission efficiency used to set ηs=0.13 in the trade-off figures.","marker":"[36]"},{"why":"Supplies the telecom frequency-conversion efficiency used together with [36] to set ηs=0.13.","marker":"[37]"},{"why":"Provides the twin-field-type security proof that the SC repeater-based QKD variant is shown to match.","marker":"[40]"}],"fun_headline_variants":["Single-click RSP boosts rate, matches fidelity","One-click remote state prep: faster and no accuracy loss","Single-click protocol for RSP: higher rate, equal fidelity","SC protocol for RSP: rate up, fidelity steady"],"cache_read_input_tokens":2688,"weakest_assumption_plain":"The advantages claimed for SC and DSC rest on the client's optical phase being stable—over one attempt for SC, over the interval between two successful clicks for DSC—because phase noise sets a fidelity ceiling of (1+e^{-σ²/2})/2 that DC does not have.","fun_headline_variants_meta":{"raw":{"variants":["Single-click RSP boosts rate, matches fidelity","One-click remote state prep: faster and no accuracy loss","Single-click protocol for RSP: higher rate, equal fidelity","SC protocol for RSP: rate up, fidelity steady"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000429,"raw_usage":{"total_tokens":2100,"prompt_tokens":882,"completion_tokens":1218,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":626,"completion_tokens_details":{"reasoning_tokens":1152}},"tokens_in":626,"tokens_out":1218,"duration_ms":12504,"temperature":1.0,"reasoning_tokens":1152,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-05T18:13:41.289467+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"On a fixed link with known client and server efficiencies and active phase stabilization, measure the accepted-state rate and fidelity of SC and DC as the client intensity is varied. The central claim fails if DC produces more accepted states per unit time than SC at the same fidelity (for example at F=0.98), or if the measured SC infidelity grows faster than ηc(4−3ηs)/(16ηs)|α|² in the small-|α|² regime, since that would indicate the leading-order error model is missing a contribution.","supporting_citations":[{"cited_title":"Efficient high-fidelity quantum computation using matter qubits and linear optics","cited_arxiv_id":null,"evidence_quote":"Supplies the prior double-click RSP protocol with a weak coherent pulse client that SC and DSC are measured against."},{"cited_title":"The security of practical quantum key distribution","cited_arxiv_id":null,"evidence_quote":"Introduces the single-click presence-absence scheme that the SC RSP protocol adapts from entanglement generation."},{"cited_title":"Blind quantum computing with weak coherent pulses","cited_arxiv_id":null,"evidence_quote":"Demonstrates single-click remote entanglement with matter qubits, grounding the SC technique experimentally."},{"cited_title":"Double-single-click protocol for remote state preparation with a weak coherent pulse source","cited_arxiv_id":null,"evidence_quote":"Provides the active phase-synchronization method and the 0.5-rad noise value used to model SC phase noise."},{"cited_title":"Alternative schemes for measurement-device-independent quantum key distribution","cited_arxiv_id":null,"evidence_quote":"Gives the linewidth-dependent phase-drift relation used to estimate DSC phase noise between consecutive clicks."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the telecom frequency-conversion efficiency used together with [36] to set ηs=0.13."},{"cited_title":"Interface between trapped-ion qubits and traveling photons with close-to-optimal efficiency","cited_arxiv_id":null,"evidence_quote":"Provides the twin-field-type security proof that the SC repeater-based QKD variant is shown to match."}],"review_version":1}