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arxiv: 1907.03242 · v1 · pith:XG6G7FBYnew · submitted 2019-07-07 · 🪐 quant-ph

Device-Independent Quantum Private Query Protocol without the Assumption of Perfect Detectors

Dan-Dan Li , Xiao-Hong Huang , Wei Huang , Fei Gao This is my paper

Pith reviewed 2026-05-25 01:40 UTC · model grok-4.3

classification 🪐 quant-ph
keywords device-independentquantum private queryimperfect detectorsquantum cryptographyBell inequalitysecurity analysisquantum information
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The pith

A device-independent quantum private query protocol can be built without assuming perfect detectors.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The earlier MRT17 protocol for device-independent quantum private query loses its security guarantees once detectors are allowed to be lossy or inefficient. The paper first exhibits an attack that exploits this gap and then supplies a revised protocol whose security proof works with imperfect detectors. A sympathetic reader cares because every real detector has some inefficiency, so the perfect-detector requirement had blocked experimental tests of the device-independent approach. The new construction keeps the certification of states and measurements inside the device-independent framework.

Core claim

When detectors are imperfect the MRT17 protocol admits an attack that compromises the privacy of the queried database, yet a modified protocol can still certify the necessary correlations via Bell inequality violation and thereby realize device-independent quantum private query without requiring ideal detectors.

What carries the argument

A revised quantum private query protocol whose device-independent security analysis explicitly incorporates detector inefficiency into the certification of the states and measurements.

If this is right

  • Device-independent quantum private query becomes compatible with the efficiencies of present single-photon detectors.
  • Security against a dishonest user continues to rest on the violation of a Bell inequality even when detectors lose photons.
  • The protocol achieves the same device-independent privacy guarantees as MRT17 without adding extra assumptions about the measurement devices.
  • Implementation no longer requires the theoretical idealization of unit-efficiency detectors.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same style of explicit modeling of detector loss may let other device-independent cryptographic primitives drop their perfect-detector assumptions.
  • Quantitative comparison of the communication overhead or key rate between the new protocol and MRT17 would clarify the practical cost of the added robustness.
  • The result indicates that device-independent certification can be strengthened rather than weakened by treating hardware non-idealities inside the proof.

Load-bearing premise

Imperfect detectors can be folded into the device-independent certification without opening a new loophole that evades the Bell-test bound.

What would settle it

An explicit attack that extracts the queried bit from the new protocol while respecting the device-independent model and the observed detector efficiencies would falsify the security claim.

Figures

Figures reproduced from arXiv: 1907.03242 by Dan-Dan Li, Fei Gao, Wei Huang, Xiao-Hong Huang.

Figure 1
Figure 1. Figure 1: FIG. 1. The framework of MDI QPQ. MDI indicates that [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. The framework of DI-QPQ. The grey box represents [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. The relation among [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. The relation between the value of [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. The relation between the value of [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
read the original abstract

The first device-independent quantum private query protocol (MRT17) which is proposed by Maitra \emph{et al.} [Phys. Rev. A 95, 042344 (2017)] to enhance the security through the certification of the states and measurements. However, the MRT17 protocol works under an assumption of perfect detectors, which increases difficulty in the implementations. Therefore, it is crucial to investigate what would affect the security of this protocol if the detectors were imperfect. Meanwhile, Maitra \emph{et al.} also pointed out that this problem remains open. In this paper, we analyze the security of MRT17 protocol when the detectors are imperfect and then find that this protocol is under attack in the aforementioned case. Furthermore, we propose device-independent QPQ protocol without the assumption of perfect detectors. Compared with MRT17 protocol, our protocol is more practical without relaxing the security in the device-independent framework.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The paper analyzes the security of the MRT17 device-independent quantum private query protocol under imperfect detectors, shows that it becomes vulnerable to attacks, and proposes a new DI QPQ protocol that accommodates detector inefficiency without assuming perfect detectors or relaxing the device-independent security guarantee.

Significance. If the security reduction for the new protocol holds with an explicit loss model that preserves the DI certification, the result would close the open problem identified in MRT17 and improve the practicality of device-independent QPQ for realistic hardware.

major comments (2)
  1. [Security proof of the new protocol] The central security claim for the proposed protocol requires an explicit derivation showing that the detector-loss model (with efficiency η<1) can be incorporated into the DI certification without introducing assumptions that weaken the entropy bound relative to MRT17. No such derivation or effective Bell inequality is provided.
  2. [Analysis of MRT17 under imperfect detectors] The attack on MRT17 with imperfect detectors is asserted but the concrete attack strategy, the post-selection rule, and the quantitative violation of the original security bound are not shown; without these the claim that the protocol is 'under attack' cannot be verified as load-bearing.
minor comments (1)
  1. [Abstract] The abstract cites MRT17 only by year and journal; the full reference should appear at first mention for completeness.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We respond to each major comment below and will incorporate the requested clarifications in a revised version.

read point-by-point responses

  1. Referee: [Security proof of the new protocol] The central security claim for the proposed protocol requires an explicit derivation showing that the detector-loss model (with efficiency η<1) can be incorporated into the DI certification without introducing assumptions that weaken the entropy bound relative to MRT17. No such derivation or effective Bell inequality is provided.

    Authors: We agree that the security analysis would be strengthened by an explicit step-by-step derivation. In the revision we will add a dedicated subsection that derives the effective Bell inequality under the loss model η<1, shows how the min-entropy bound is obtained from the observed statistics, and confirms that no additional assumptions are introduced that weaken the bound relative to MRT17. revision: yes

  2. Referee: [Analysis of MRT17 under imperfect detectors] The attack on MRT17 with imperfect detectors is asserted but the concrete attack strategy, the post-selection rule, and the quantitative violation of the original security bound are not shown; without these the claim that the protocol is 'under attack' cannot be verified as load-bearing.

    Authors: We acknowledge that the attack description in the current text is concise. In the revision we will expand the relevant section to specify the concrete attack strategy, the post-selection rule used by the dishonest party, and quantitative results (including the observed violation of the original security bound) for representative values of detector efficiency η<1. revision: yes

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained against external benchmarks

full rationale

The paper analyzes the MRT17 protocol (by independent authors) under imperfect detectors, identifies an attack, and proposes a new DI QPQ protocol. No equations or steps are shown reducing a claimed prediction or security bound to a fitted parameter, self-citation chain, or definitional equivalence. Detector modeling is treated as an explicit extension rather than smuggled via ansatz or prior self-work. The central claim rests on external DI certification techniques and does not collapse to its inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no explicit free parameters, axioms, or invented entities; the ledger is therefore empty except for the general note that any device-independent security proof must invoke standard no-signaling or Bell-test assumptions whose status cannot be verified here.

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Reference graph

Works this paper leans on

39 extracted references · 39 canonical work pages

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    xi = 0(1) represents the measuring ob- servablesσz(σx); yi = 0(1) represents the measur- ing observables σ x+σ z√ 2 (σ z − σ x√ 2 )

    xi ∈ { 0, 1} and yi ∈ { 0, 1} are chosen uniformly at random. xi = 0(1) represents the measuring ob- servablesσz(σx); yi = 0(1) represents the measur- ing observables σ x+σ z√ 2 (σ z − σ x√ 2 ). The first and second particle of the entangled state can be measured, re- spectively. When the measurement result is |0⟩ or |+⟩ (|1⟩ or |−⟩), then ai = 0(1). Simil...

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    Now, if the shared state is |00⟩+|11⟩√ 2 , then ˆICHSH = 2 √ 2, which corresponds to the maximal violation in quantum theory

    CHSH Bell correlation function is described as ˆICHSH =E(X0Y0) +E(X0Y1) +E(X1Y0) − E(X1Y1), where E(X0Y0) = ∑ ai,b i (− 1)ai+bip(ai,b i|xi = 0,y i = 0), and others have similar definitions. Now, if the shared state is |00⟩+|11⟩√ 2 , then ˆICHSH = 2 √ 2, which corresponds to the maximal violation in quantum theory. In a general CHSH Bell test, the shared st...

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    For CHSH Bell game, i ∈ { 1,..., ⌈γN ⌉}, (a) Bob chooses xi ∈ { 0, 1} and yi ∈ { 0, 1} uni- formly at random. (b) If xi = 0(1), he measures the first par- ticle of the entangled state in the basis {|0⟩, |1⟩}({|+⟩, |−⟩}), then denote ai = 0(1) when the measurement result is |0⟩ or |+⟩ (|1⟩ or |−⟩). In the same manner, if yi = 0(1), he measures the second pa...

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    Next, Bob uses the remaining ⌊(1− γ)N ⌋ entangled pairs to proceed to QPQ steps

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    Hence, based on the state ( 44) and statistical method 2, Bob gets ICHSH = sinθ(sinψ 1 + sinψ 2) + 2 √ 1 4 − ǫ2(cosψ 1 − cosψ 2)

    can be referred to Appendix B. Hence, based on the state ( 44) and statistical method 2, Bob gets ICHSH = sinθ(sinψ 1 + sinψ 2) + 2 √ 1 4 − ǫ2(cosψ 1 − cosψ 2). (19) This value cannot violate the condition ( 17), the proof can be given in Appendix C. To summarize, these two statistical methods can de- tect Alice’s attack that the states are not in the pre...

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    is ICHSH = 8 − 2[sinθ(sinψ 1 + sinψ 2) + 2 √ 1 4 − ǫ2 η (cosψ 1 − cosψ 2)] + 3[sinθ(sinψ 1 + sinψ 2)+ 2 √ 1 4 − ǫ2(cosψ 1 − cosψ 2)] − 8. (21) When η and ǫ satisfy the following cases: Case 1: 2 1 + √ 2 <η < 8 − 2A 8 − 2A +B < 1, ǫ ∈ (− 1 2, 0) ∪ (0, 1 2 ); (22) Case 2: 2 1 + √ 2 < 8 − 2A 8 − 2A +B <η < 8 − 2A − 2B 8 − 2A − 2B, ǫ ∈ (− √ (3η − 2)2B2 − C2 2...

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    For CHSH Bell test, i ∈ { 1,..., ⌈γN ⌉}, (a) Bob chooses xi ∈ { 0, 1} and yi ∈ { 0, 1} uni- formly at random. (b) If xi = 0(1), he measures the first par- ticle of the entangled state in the basis {|0⟩, |1⟩}({|+⟩, |−⟩}), then denotes ai = 0(1) when the measurement result is |0⟩ or |+⟩ (|1⟩ or |−⟩). In the same manner, if yi = 0(1), he measures the second p...

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    ξ = √ 1 2⌈γN ⌉ ln 1 εCHSH , v = √ (N − ⌈γN ⌉ + 1)⌊(1 − γ)N ⌋2 ln 1 εQP Q 2⌈γN ⌉N 3 , (36) εCHSH and εQPQ are negligible small values

    is still satisfied in the QPQ part with a negli- gible statistical deviation v, where ICHSH represents the observed value of CHSH Bell test, and ¯ICHSH represents the value of CHSH Bell test in predetermined states and measurements in our protocol. ξ = √ 1 2⌈γN ⌉ ln 1 εCHSH , v = √ (N − ⌈γN ⌉ + 1)⌊(1 − γ)N ⌋2 ln 1 εQP Q 2⌈γN ⌉N 3 , (36) εCHSH and εQPQ are ...

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