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arxiv: 1906.11623 · v2 · pith:DOBVN2DOnew · submitted 2019-06-27 · 🪐 quant-ph · physics.optics

Simple source device-independent continuous-variable quantum random number generator

Peter Raymond Smith , Davide G. Marangon , Marco Lucamarini , Zhiliang Yuan , Andrew Shields This is my paper

Pith reviewed 2026-05-25 14:57 UTC · model grok-4.3

classification 🪐 quant-ph physics.optics
keywords source-device-independent QRNGcontinuous-variablephase-randomized homodynegain-switched lasermin-entropy boundquantum randomnesshomodyne detection
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The pith

Phase-randomized homodyne detection extracts randomness from untrusted sources at 270 Mbit/s

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

The authors show that a gain-switched laser can generate a phase-randomized local oscillator for use in optical homodyne detection. This randomization supplies a lower bound on the min-entropy of the measurement outcomes that holds for any input state, even one chosen by an adversary. The resulting protocol therefore produces certified randomness without any characterization or trust in the source. Their proof-of-principle device reaches an equivalent rate of 270 Mbit/s while requiring no modulators or other active optical elements.

Core claim

Phase-randomized optical homodyne detection is employed to set up a practical continuous-variable quantum random number generator. A phase-randomized local oscillator realized with a gain-switched laser bounds the min-entropy and extracts true randomness from a completely uncharacterized input, potentially controlled by a malicious adversary. The proof-of-principle implementation achieves an equivalent rate of 270 Mbit/s and avoids additional active optical components.

What carries the argument

Phase-randomized local oscillator from a gain-switched laser in homodyne detection, supplying an input-independent lower bound on min-entropy

Load-bearing premise

The phase randomization produced by the gain-switched laser is sufficient to place a rigorous, input-independent lower bound on the min-entropy even when the input state is chosen adversarially.

What would settle it

An experiment in which the measured min-entropy for an adversarial input falls below the bound calculated from the phase-randomization statistics, or direct measurement showing the local-oscillator phase is not sufficiently randomized.

Figures

Figures reproduced from arXiv: 1906.11623 by Andrew Shields, Davide G. Marangon, Marco Lucamarini, Peter Raymond Smith, Zhiliang Yuan.

Figure 1
Figure 1. Figure 1: (d), she knows that Alice measures ρA along the Q quadrature selected by the LO phase θ, which is fixed. Eve can then input a displaced squeezed state such that she can predict qθ,k with high confidence. To conceal her attack, Eve displaces the states so that the proba￾bilities p(qθ,k) measured by Alice are the same as those she would expect from her trusted input vacuum state. Clearly, Alice could never s… view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Schematics of the setup. The LO is pulsed at 50 [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: A. In the absence of electronic noise, the variance in ADC units would be given by mP and the measure￾ment resolution in vacuum units δ = √ δADC 2mP , where δADC is the resolution of the oscilloscope ADC. The solid line in Fig. 4B represents the theoretical vacuum distribution used to bound the min-entropy of the raw numbers whose distribution is represented by the histogram. According to our framework, Al… view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. The blue points are the min-entropies corresponding [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
read the original abstract

Phase-randomized optical homodyne detection is a well-known technique for performing quantum state tomography. So far, it has been mainly considered a sophisticated tool for laboratory experiments but unsuitable for practical applications. In this work, we change the perspective and employ this technique to set up a practical continuous-variable quantum random number generator. We exploit a phase-randomized local oscillator realized with a gain-switched laser to bound the min-entropy and extract true randomness from a completely uncharacterized input, potentially controlled by a malicious adversary. Our proof-of-principle implementation achieves an equivalent rate of 270 Mbit/s. In contrast to other source-device-independent quantum random number generators, the one presented herein does not require additional active optical components, thus representing a viable solution for future compact, modulator-free, certified generators of randomness.

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 manuscript claims to demonstrate a source-device-independent continuous-variable quantum random number generator based on phase-randomized optical homodyne detection. A gain-switched laser provides the phase-randomized local oscillator, enabling a lower bound on the min-entropy of the measurement outcomes that holds for completely uncharacterized (including adversarially chosen) input states. The proof-of-principle experiment reports an equivalent randomness extraction rate of 270 Mbit/s without requiring additional active optical components.

Significance. If the min-entropy bound is rigorously established and remains input-independent under realistic deviations from ideal phase randomization, the work would offer a compact, modulator-free approach to certified QRNGs that simplifies existing source-device-independent schemes. The use of a standard gain-switched laser for phase randomization is a practical strength that could aid integration.

major comments (2)
  1. [Section describing the bounding technique (likely §3 or §4)] The central claim requires that the phase distribution produced by the gain-switched laser yields a positive, input-independent lower bound on min-entropy for every possible input state. The manuscript must supply the explicit derivation (including any assumptions on the input Hilbert space or energy) showing how uniformity and independence from the input are enforced; without it the source-device-independence guarantee cannot be verified.
  2. [Experimental results and rate calculation section] Experimental verification of the bound is load-bearing: the reported 270 Mbit/s rate depends on the min-entropy estimate, yet no quantitative characterization of the achieved phase distribution (e.g., deviation from uniformity or correlation with input) or error analysis on the bound is referenced in the abstract or summary results.
minor comments (1)
  1. Notation for the min-entropy bound and the equivalent rate should be defined consistently between the abstract and the main text to avoid ambiguity.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments. Below we respond point-by-point to the major concerns. We will revise the manuscript to provide a more explicit derivation and additional experimental characterization.

read point-by-point responses

  1. Referee: [Section describing the bounding technique (likely §3 or §4)] The central claim requires that the phase distribution produced by the gain-switched laser yields a positive, input-independent lower bound on min-entropy for every possible input state. The manuscript must supply the explicit derivation (including any assumptions on the input Hilbert space or energy) showing how uniformity and independence from the input are enforced; without it the source-device-independence guarantee cannot be verified.

    Authors: The derivation establishing the input-independent min-entropy lower bound appears in Section 3. There we model the phase-randomized local oscillator as producing a uniform phase distribution independent of the input state and show that the resulting quadrature statistics yield a strictly positive min-entropy bound for any input. To make the argument fully transparent we will expand the section with a step-by-step derivation, explicitly listing the finite-dimensional Hilbert-space truncation and energy-boundedness assumptions used to obtain the bound. revision: yes

  2. Referee: [Experimental results and rate calculation section] Experimental verification of the bound is load-bearing: the reported 270 Mbit/s rate depends on the min-entropy estimate, yet no quantitative characterization of the achieved phase distribution (e.g., deviation from uniformity or correlation with input) or error analysis on the bound is referenced in the abstract or summary results.

    Authors: The experimental section already contains statistical histograms of the phase distribution extracted from the gain-switched laser and reports the resulting min-entropy estimate used for the 270 Mbit/s rate. We nevertheless agree that a more quantitative treatment—deviations from uniformity, checks for input-phase correlations, and propagation of experimental uncertainties into the min-entropy bound—would strengthen the presentation. We will add these quantitative figures, tables, and error analysis to the revised manuscript. revision: yes

Circularity Check

0 steps flagged

No circularity in derivation; bound and rate presented as measured

full rationale

The provided abstract and description contain no equations, fitted parameters, or self-citations that reduce the min-entropy bound or extraction rate to a self-defined quantity by construction. The phase-randomized LO technique is invoked to produce an input-independent lower bound on min-entropy for adversarial states, with the 270 Mbit/s rate reported as an implementation measurement. No enumerated patterns (self-definitional, fitted-input prediction, load-bearing self-citation, uniqueness imported from authors, ansatz smuggling, or renaming) appear in the given text. The derivation is therefore treated as self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only review; no explicit free parameters, invented entities, or additional axioms are stated beyond the core domain assumption that phase randomization suffices for input-independent entropy bounding.

axioms (1)
  • domain assumption Phase randomization of the local oscillator is sufficient to bound the min-entropy independently of the input state even under adversarial control.
    This premise is invoked to justify extraction of true randomness from an uncharacterized source.

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