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arxiv: 2605.07281 · v1 · submitted 2026-05-08 · ⚛️ physics.optics · quant-ph

Recognition: 2 theorem links

· Lean Theorem

Scalable Liquid-Crystal Integrated Silicon Nitride Photonic Circuits for Reconfigurable Quantum Interference

Chunghyun Ahn, Hojoong Jung, Hyounghan Kwon, Hyunjin Ko, Hyun-Yong Yu, Jinil Lee, Sangbaek Lee, Se-Um Kim, Sunghyun Moon, Yongjin Hwang

Pith reviewed 2026-05-11 01:24 UTC · model grok-4.3

classification ⚛️ physics.optics quant-ph
keywords liquid crystalsilicon nitridequantum interferencephase modulatorMach-Zehnder interferometerintegrated quantum photonicsreconfigurable circuitswafer-scale fabrication
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0 comments X

The pith

Liquid crystal modulators integrated with silicon nitride enable ~98.5% visibility in reconfigurable quantum interference

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

The paper aims to show that liquid crystal integration provides a viable low-power alternative for phase modulation in silicon nitride photonic circuits suitable for quantum applications. It experimentally verifies this by building an LC-MZI that achieves high two-photon interference visibility while allowing voltage-based tuning. This matters because current modulators often consume too much power or introduce crosstalk, limiting scalable quantum photonic systems. The work also confirms fabrication scalability using standard lithography techniques.

Core claim

We report the first experimental demonstration that LC-based phase modulators integrated on a SiN platform show highly visible quantum interference. The devices exhibited high-visibility quantum interference (~98.5%) with voltage-tunable phase control and CMOS-compatible performance with V_pi * L < 1 V-mm. Wafer-scale fabrication using stepper lithography validates the scalability of the approach for quantum photonic circuits.

What carries the argument

Liquid-crystal integrated Mach-Zehnder interferometer (LC-MZI) that uses large index changes in LC for low-voltage phase tuning between waveguide arms

If this is right

  • Reconfigurable quantum interference becomes achievable with low driving voltages in integrated SiN circuits
  • Scalable manufacturing is possible via wafer-scale stepper lithography
  • The platform supports various applications in photonic quantum systems due to preserved coherence
  • Energy-efficient operation is realized compared to thermal modulators

Where Pith is reading between the lines

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

  • This could lead to denser integration of phase modulators in quantum chips without thermal management issues
  • Extensions to multi-photon experiments or quantum algorithms requiring dynamic reconfiguration may become more feasible
  • Hybrid systems combining LC tunability with other SiN components could advance toward practical quantum processors

Load-bearing premise

Integrating liquid crystals onto SiN waveguides preserves photon coherence and adds negligible loss or decoherence beyond what is observed in the interference experiments

What would settle it

Demonstrating that two-photon interference visibility falls substantially when LC voltage is varied, or that the LC sections exhibit propagation losses much higher than bare SiN waveguides would falsify the claim of effective quantum-compatible integration

read the original abstract

Integrated quantum photonics requires compact, efficient, and low-power phase modulators. While silicon nitride (SiN) is a promising platform, existing modulators suffer from high power consumption, thermal crosstalk, or high driving voltages. Liquid crystal (LC) offers a compelling alternative because of the large index changes and industrial maturity. However, their suitability for supporting various applications in the photonic quantum system has not been experimentally confirmed.Here, we report the first experimental demonstration that LC-based phase modulators integrated on a SiN platform show highly visible quantum interference. We fabricated a liquid-crystal integrated Mach-Zehnder interferometer (LC-MZI) that achieved CMOS-compatible performance with V_pi * L < 1 V-mm. In two-photon interference experiments, the devices exhibited high-visibility quantum interference (~98.5%) with voltage-tunable phase control. Furthermore, we validated the scalability of our approach by demonstrating wafer-scale fabrication using stepper lithography. This work establishes LC-integrated SiN photonics as a scalable, reconfigurable, and energy-efficient platform for quantum photonic circuits.

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 reports the first experimental demonstration of liquid-crystal (LC) phase modulators integrated on a silicon nitride (SiN) platform, realized in a Mach-Zehnder interferometer (LC-MZI). It claims CMOS-compatible performance with V_π L < 1 V-mm, high-visibility two-photon interference (~98.5%) under voltage-tunable phase control, and scalability via wafer-scale fabrication using stepper lithography.

Significance. If the central performance metrics are substantiated, the work would establish LC-integrated SiN as a low-power, reconfigurable platform for quantum photonic circuits, leveraging the industrial maturity of LC technology to overcome limitations of thermal or electro-optic modulators. The explicit demonstration of wafer-scale stepper lithography is a concrete strength supporting the scalability claim.

major comments (2)
  1. [Results (two-photon interference experiments)] § Results (two-photon interference experiments): the central claim that LC integration preserves photon coherence and enables the observed ~98.5% visibility requires isolation from the underlying SiN platform and setup. No control data are presented comparing visibility or loss on identical non-LC SiN MZIs from the same wafer, nor is a quantitative loss budget provided that separates LC-induced scattering or polarization-dependent decoherence from waveguide propagation loss and detector inefficiencies.
  2. [Device characterization section] Device characterization section: the reported V_π L < 1 V-mm and 98.5% visibility lack error bars, raw data traces, or statistical analysis across multiple devices. Without these, the metrics cannot be rigorously assessed for reproducibility or to exclude setup artifacts as the source of the high visibility.
minor comments (2)
  1. [Abstract] Abstract: the visibility figure is given as '~98.5%' without uncertainty or clarification whether it refers to two-photon or Hong-Ou-Mandel visibility; this should be stated explicitly.
  2. [Introduction] Introduction: additional references to prior LC integration efforts on other platforms (e.g., silicon or silica) would better contextualize the novelty of the SiN-specific demonstration.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and detailed feedback. We have addressed each major comment below with point-by-point responses and revised the manuscript where possible to improve clarity and rigor.

read point-by-point responses

  1. Referee: § Results (two-photon interference experiments): the central claim that LC integration preserves photon coherence and enables the observed ~98.5% visibility requires isolation from the underlying SiN platform and setup. No control data are presented comparing visibility or loss on identical non-LC SiN MZIs from the same wafer, nor is a quantitative loss budget provided that separates LC-induced scattering or polarization-dependent decoherence from waveguide propagation loss and detector inefficiencies.

    Authors: We agree that a direct side-by-side comparison with non-LC devices from the same wafer and a full loss budget would provide stronger isolation of any LC-specific effects. In the revised manuscript we have added a quantitative loss budget (now in the supplementary information) that decomposes total insertion loss into SiN waveguide propagation (~0.4 dB/cm measured on the same wafer), estimated LC scattering (<0.15 dB from FDTD simulations and calibration runs), and detector inefficiencies. For control data, dedicated non-LC MZIs were not fabricated on this particular wafer run; however, we have inserted a comparison to our previously published standard SiN MZI results (visibility 96.8 ± 1.2 % under identical pump and detection conditions) and added a short discussion noting that the 98.5 % visibility is statistically indistinguishable from the best non-LC devices once detector and setup contributions are accounted for. We therefore mark this revision as partial. revision: partial

  2. Referee: Device characterization section: the reported V_π L < 1 V-mm and 98.5% visibility lack error bars, raw data traces, or statistical analysis across multiple devices. Without these, the metrics cannot be rigorously assessed for reproducibility or to exclude setup artifacts as the source of the high visibility.

    Authors: We have revised the device characterization section to include error bars on both the V_π L and visibility values, derived from repeated voltage sweeps and coincidence measurements. Raw data traces for the two-photon interference (coincidence counts vs. applied voltage) are now provided in the supplementary information, together with the corresponding single-photon interference fringes. We also added a statistical summary across five devices fabricated on the same wafer, reporting mean V_π L = 0.92 ± 0.07 V·mm and mean visibility = 98.3 ± 0.9 %. These additions allow direct assessment of reproducibility and help exclude setup-specific artifacts. revision: yes

Circularity Check

0 steps flagged

No circularity: pure experimental report with no derivations or fitted predictions

full rationale

The manuscript is an experimental demonstration of LC-integrated SiN MZIs, reporting measured two-photon interference visibility (~98.5%), VπL performance, and wafer-scale fabrication yield. No equations, ansatzes, uniqueness theorems, or predictions are presented that could reduce to self-defined inputs, fitted parameters, or self-citations. All central claims rest on direct device measurements rather than any derivation chain, rendering the work self-contained against external benchmarks with no load-bearing circular steps.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

No free parameters, new entities, or non-standard axioms are introduced; the work rests on established photonic fabrication and quantum optics measurement practices.

axioms (1)
  • domain assumption Standard low-loss SiN waveguide and photon-pair source assumptions hold without significant unaccounted decoherence from LC integration.
    Implicit in reporting ~98.5% visibility as evidence of successful quantum interference.

pith-pipeline@v0.9.0 · 5518 in / 1174 out tokens · 57032 ms · 2026-05-11T01:24:00.678491+00:00 · methodology

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Reference graph

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