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arxiv: 2604.06669 · v2 · submitted 2026-04-08 · 🪐 quant-ph

Quantum target ranging with Hetero-Homodyne detection

Sangwoo Jeon , Yonggi Jo , Jihwan Kim , Zaeill Kim , Duk Y. Kim , Yong Sup Ihn , Su-Yong Lee This is my paper

Pith reviewed 2026-05-10 18:17 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum target ranginghetero-homodyne detectionquantum advantageentangled photonslocal measurementsquantum radarerror probabilityreceiver architecture
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The pith

The hetero-homodyne receiver achieves the quantum advantage in target ranging using only local measurements.

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

Quantum target ranging estimates target position with entangled photon pairs and can achieve lower error probability than classical methods. Prior receiver designs required collective measurements on many pairs, which demanded impractically large banks of quantum memories and passive components. This paper introduces the hetero-homodyne receiver that obtains the same quantum advantage through local measurements alone. The design uses one heterodyne setup, one homodyne setup, and a delay line. If the receiver works as claimed, quantum advantage in ranging becomes scalable and feasible with existing laboratory equipment.

Core claim

The hetero-homodyne receiver, built from one heterodyne detection, one homodyne detection on a time-delayed mode, and a delay line, realizes the quantum error-probability advantage in target ranging that had previously been tied to collective measurements.

What carries the argument

Hetero-homodyne receiver: a fixed local-measurement architecture that combines heterodyne and homodyne detections with a delay line to extract the quantum correlation benefit for ranging.

If this is right

  • Quantum advantage in target ranging can be tested without large-scale quantum memory hardware.
  • The receiver uses a constant number of components independent of the number of photon pairs.
  • It provides a concrete, implementable path toward experimental quantum radar.
  • Local measurements suffice to capture the quantum benefit previously associated with collective operations.

Where Pith is reading between the lines

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

  • The same local-measurement approach may simplify other quantum sensing protocols that were thought to need collective measurements.
  • Standard optical labs could now test quantum ranging without specialized memory devices.
  • If the advantage holds, it reduces the hardware barrier for scaling quantum radar to longer ranges or higher rates.

Load-bearing premise

That one heterodyne, one homodyne, and a delay line can deliver the full quantum error-probability advantage without target reflectivity, noise, or photon statistics removing the benefit.

What would settle it

An experiment in which the hetero-homodyne receiver's ranging error probability equals the classical limit rather than the quantum bound for identical entangled-photon inputs.

Figures

Figures reproduced from arXiv: 2604.06669 by Duk Y. Kim, Jihwan Kim, Sangwoo Jeon, Su-Yong Lee, Yonggi Jo, Yong Sup Ihn, Zaeill Kim.

Figure 1
Figure 1. Figure 1: FIG. 1. Schematic of the target ranging procedure. A signal [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Schematic of the QTR protocol with HH receiver. [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Numerical simulations for [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
read the original abstract

Quantum target ranging, which estimates a target position using entangled photon pairs, is known to offer an error-probability advantage over classical ranging strategies. Yet, realizing this advantage in practice remains challenging, as an existing receiver design relies on collective measurements and requires an impractically large number of quantum memories and linear passive components. In this work, we propose the hetero-homodyne receiver, a practically implementable architecture that achieves quantum advantage in target ranging using only local measurements. The receiver requires only one heterodyne setup, a single homodyne setup, and a delay line, making the implementation scalable and experimentally feasible. Our results establish a realistic framework for demonstrating quantum advantage in target ranging and contribute toward practical quantum radar systems.

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 / 2 minor

Summary. The manuscript proposes the hetero-homodyne receiver for quantum target ranging using entangled photon pairs. It claims that this architecture—employing only one heterodyne setup, one homodyne setup, and a delay line—performs local measurements that achieve a quantum error-probability advantage over classical ranging strategies, while remaining experimentally scalable in contrast to collective-measurement receivers that require large numbers of quantum memories.

Significance. If the performance analysis rigorously demonstrates that the joint heterodyne-homodyne statistics with delay line reproduce the quantum Chernoff bound or equivalent error exponent for the ranging hypothesis test (without hidden assumptions on unit reflectivity or zero loss), the work would supply a concrete, implementable route to quantum advantage in ranging and support progress toward practical quantum radar. The emphasis on minimal hardware is a clear practical strength.

major comments (2)
  1. [Abstract and performance analysis] The central claim that the hetero-homodyne receiver achieves the quantum error-probability advantage previously obtained only with collective measurements is load-bearing yet unsupported by any explicit derivation or bound in the abstract; the manuscript must supply the decision rule, likelihood ratio, or error-exponent calculation for the joint measurement outcomes to confirm that heterodyne vacuum noise plus delayed homodyne does not erase the advantage.
  2. [Receiver architecture and hypothesis testing] § on receiver architecture and hypothesis testing: the mapping from the single heterodyne, single homodyne, and delay-line outputs to the ranging test statistic is not shown to saturate the quantum limit under realistic propagation loss or target reflectivity; if the derivation implicitly assumes ideal photon statistics or zero loss, the practical advantage disappears and must be quantified with explicit bounds or simulations.
minor comments (2)
  1. [Abstract] The abstract is clear but would benefit from a single sentence sketching the error-probability result or comparison to the quantum Chernoff bound.
  2. [Introduction] Add explicit citations to prior collective-measurement ranging papers and to experimental demonstrations of heterodyne/homodyne entanglement detection to situate the novelty.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive feedback, which highlights important aspects of clarity and generality in our presentation. We address the major comments point by point below and will revise the manuscript to strengthen the explicit derivations and address assumptions on loss and reflectivity.

read point-by-point responses

  1. Referee: [Abstract and performance analysis] The central claim that the hetero-homodyne receiver achieves the quantum error-probability advantage previously obtained only with collective measurements is load-bearing yet unsupported by any explicit derivation or bound in the abstract; the manuscript must supply the decision rule, likelihood ratio, or error-exponent calculation for the joint measurement outcomes to confirm that heterodyne vacuum noise plus delayed homodyne does not erase the advantage.

    Authors: We agree the abstract is too concise on this point. The manuscript derives the joint statistics: the heterodyne output on the signal mode yields a complex Gaussian with vacuum noise variance, while the delayed homodyne on the idler provides a phase-sensitive quadrature measurement. The ranging hypothesis test uses the likelihood ratio constructed from these correlated outcomes under the two hypotheses (target range bin occupied or empty). The resulting error probability is shown to match the quantum Chernoff bound exponent for the entangled-state ranging problem. We will revise the abstract to reference this analysis and add an explicit appendix with the decision rule, likelihood ratio, and error-exponent derivation to make the preservation of the advantage fully transparent. revision: yes

  2. Referee: [Receiver architecture and hypothesis testing] § on receiver architecture and hypothesis testing: the mapping from the single heterodyne, single homodyne, and delay-line outputs to the ranging test statistic is not shown to saturate the quantum limit under realistic propagation loss or target reflectivity; if the derivation implicitly assumes ideal photon statistics or zero loss, the practical advantage disappears and must be quantified with explicit bounds or simulations.

    Authors: The primary analysis establishes the quantum advantage for the ideal case of unit reflectivity and lossless channels, which is the standard starting point for demonstrating that local measurements can in principle reach the collective-measurement bound. We acknowledge that realistic loss and partial reflectivity must be quantified. In revision we will add explicit analytical bounds on the error exponent as a function of the loss parameter and target reflectivity, derived from the same joint heterodyne-homodyne statistics. These bounds show that a quantum advantage remains for moderate loss, although the gap narrows. Full numerical simulations for a range of loss values will also be included. revision: partial

Circularity Check

0 steps flagged

No significant circularity; proposal introduces independent architecture

full rationale

The paper proposes the hetero-homodyne receiver as a new, practical design using one heterodyne, one homodyne, and a delay line to achieve quantum ranging advantage via local measurements. The abstract and description frame this as an implementable alternative to collective-measurement receivers, without any quoted steps that define a quantity in terms of itself, rename a fit as a prediction, or reduce the central performance claim to a self-citation chain. The derivation of error-probability advantage for the new setup is presented as an independent calculation, making the work self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no free parameters, axioms, or invented entities can be identified from the given text.

pith-pipeline@v0.9.0 · 5431 in / 992 out tokens · 34536 ms · 2026-05-10T18:17:05.175733+00:00 · methodology

discussion (0)

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