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arxiv: 2509.17989 · v2 · submitted 2025-09-22 · ⚛️ physics.optics · quant-ph

Sub-femtosecond stabilization of multicore fiber for high-fidelity quantum networking at 100% duty cycle

Takuma Nakamura , Nazanin Hoghooghi , Nicolas Fontaine , Tetsuya Hayashi , Takuji Nagashima , Nicholas V. Nardelli , Dileep V. Reddy , Martin J. Stevens
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Tara Fortier Lynden K. Shalm Franklyn Quinlan
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Pith reviewed 2026-05-18 14:16 UTC · model grok-4.3

classification ⚛️ physics.optics quant-ph
keywords multicore fiberquantum networkingphase stabilizationattosecond jitteroptical crosstalkRaman scatteringduty cyclenoise correlation
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The pith

Multicore fiber uses noise correlation between cores to stabilize quantum channels to 100 attoseconds over 40 km at full duty cycle.

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

This paper shows that multicore fibers can solve the problem of co-existing quantum and classical light in networks by placing them in separate but correlated cores. The high noise correlation allows phase stabilization of the quantum core using measurements from the stabilization core. This achieves 100 attosecond integrated jitter and enables continuous operation without interrupting the quantum channel for stabilization. It maintains very low spurious photon rates due to low optical crosstalk. A reader cares because it points to a practical way to build high-fidelity, always-on quantum networks over long distances.

Core claim

By operating quantum and stabilization light in separate cores of a 7-core multicore fiber, phase information from the stabilization core stabilizes the quantum core, achieving 100 attosecond integrated jitter over 40 km of spooled fiber. This setup provides 100% duty cycle on the quantum channel, cycle-slip-free stabilization over 6 hours, and a Raman scattering-induced spurious photon rate of only 0.01 photons per second in 100 GHz bandwidth, thanks to frequency detuning and 40 dB noise rejection from low crosstalk.

What carries the argument

The high degree of noise correlation between cores confined in the same cladding of the multicore fiber, used to transfer phase information for stabilization without mixing signals in the same core.

Load-bearing premise

The noise in different cores of the multicore fiber is highly correlated enough that stabilization derived from one core works accurately for another.

What would settle it

Measuring the integrated jitter when stabilizing a core using phase data from a non-correlated or distant core and finding it significantly worse than 100 attoseconds would challenge the claim.

Figures

Figures reproduced from arXiv: 2509.17989 by Dileep V. Reddy, Franklyn Quinlan, Lynden K. Shalm, Martin J. Stevens, Nazanin Hoghooghi, Nicholas V. Nardelli, Nicolas Fontaine, Takuji Nagashima, Takuma Nakamura, Tara Fortier, Tetsuya Hayashi.

Figure 1
Figure 1. Figure 1: MCF as a solution for classical and quantum light co [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: (a) Schematic of the experimental setup of the MCF fiber link. (b) Phase noise spectra of the free [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
read the original abstract

Originally envisioned as a solution for the capacity crunch in telecommunications networks, multicore fibers (MCF) are contributing to scientific fields beyond telecom, such as sensing and metrology. Confined within the same cladding, the cores of MCF have a high degree of noise correlation which can be harnessed for a variety of applications. Here, we investigate MCF as a solution to the challenging problem of quantum and classical light co-existence in quantum networks by operating the quantum and stabilization light in separate but highly correlated cores of a 7-core MCF. Over 40 km of spooled fiber, we achieved 100 attosecond integrated jitter on one core by using phase information derived from another core. This allows for 100% duty cycle on a quantum channel while maintaining a low spurious photon rate from crosstalk between stabilization and quantum channels. With cycle-slip-free stabilization over 6 hours, frequency detuning between designated stabilization and quantum channels, and an additional 40 dB rejection of noise photons provided by the low optical crosstalk between cores, we achieved a Raman scattering-induced spurious photon rate of only 0.01 photons/s in 100 GHz bandwidth. Our results with MCF are a promising approach to ultra-stable quantum networks with 100% duty cycle on the quantum channel.

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 reports an experimental demonstration using a 7-core multicore fiber (MCF) to stabilize the phase of a quantum channel by deriving phase information from a separate but correlated core. Over 40 km of spooled fiber, they achieve 100 attosecond integrated jitter, enabling 100% duty cycle operation on the quantum channel with a spurious photon rate of 0.01 photons/s from Raman scattering, supported by 40 dB rejection from low optical crosstalk and frequency detuning between channels. Cycle-slip-free stabilization is demonstrated over 6 hours.

Significance. If the experimental results are confirmed, this work represents a significant advancement in quantum networking by solving the problem of classical-quantum light coexistence in fiber links. The high noise correlation in MCF cores allows for continuous stabilization without sacrificing duty cycle, which is crucial for high-fidelity quantum communication and could impact the design of future quantum networks.

major comments (2)
  1. Abstract: The abstract states quantitative results including '100 attosecond integrated jitter' and '0.01 photons/s' but provides no error bars, raw data, detailed exclusion criteria, or full experimental methods. This is load-bearing for the central claim of sub-femtosecond stabilization at 100% duty cycle and prevents independent verification of the reported performance.
  2. Abstract: The assumption that cores within the MCF exhibit a high degree of noise correlation that can be directly transferred for phase stabilization at the 100 as level is stated but not supported by a quantified correlation coefficient, measured transfer function, or bandwidth-specific data, which is central to the stabilization result.
minor comments (1)
  1. Abstract: Clarify the exact integration bandwidth or time window used for the 'integrated jitter' metric to allow direct comparison with other stabilization techniques.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for highlighting these points regarding the abstract. We address each comment below and indicate where revisions will be made to strengthen the presentation.

read point-by-point responses

  1. Referee: Abstract: The abstract states quantitative results including '100 attosecond integrated jitter' and '0.01 photons/s' but provides no error bars, raw data, detailed exclusion criteria, or full experimental methods. This is load-bearing for the central claim of sub-femtosecond stabilization at 100% duty cycle and prevents independent verification of the reported performance.

    Authors: The abstract is a concise summary of the principal results. The supporting experimental methods, data processing, error analysis, and raw measurement details are provided in the main text, including the sections describing the experimental setup, phase noise measurements, and Raman scattering characterization, along with the associated figures that show the time-series data and integrated jitter spectra. We agree that the abstract would benefit from brief indications of the precision of the reported figures. We will therefore revise the abstract to include approximate uncertainties for the key metrics (jitter and spurious photon rate) while preserving its length and readability. Detailed raw data, exclusion criteria, and full methods are appropriately retained in the body of the paper rather than the abstract. revision: partial

  2. Referee: Abstract: The assumption that cores within the MCF exhibit a high degree of noise correlation that can be directly transferred for phase stabilization at the 100 as level is stated but not supported by a quantified correlation coefficient, measured transfer function, or bandwidth-specific data, which is central to the stabilization result.

    Authors: The manuscript contains direct experimental quantification of the inter-core noise correlation, including measured correlation coefficients, the observed phase transfer between cores, and the resulting stabilization bandwidth that yields the reported 100 as integrated jitter. These data are presented in the results section through comparative phase-noise spectra and stabilization performance plots. The abstract summarizes this body of evidence as a 'high degree of noise correlation.' To make the summary more explicit, we will revise the abstract to include a representative correlation value or bandwidth reference drawn from the main-text measurements. revision: yes

Circularity Check

0 steps flagged

No significant circularity; purely experimental demonstration

full rationale

The paper reports direct experimental measurements of phase jitter (100 as integrated), cycle-slip-free operation over 6 hours, and spurious photon rates (0.01 photons/s) achieved by harnessing measured noise correlation between cores of a 7-core MCF over 40 km. No derivation chain, equations, or predictions are presented that reduce by construction to fitted inputs, self-citations, or ansatzes. The correlation is invoked as an observed physical property of MCF and transferred experimentally; all load-bearing claims are falsifiable measurement outcomes rather than self-referential theoretical steps. This matches the reader's assessment of an experimental result with no internal reduction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The demonstration rests on the established physical property of noise correlation in multicore fibers rather than new postulates or fitted parameters introduced in this work.

axioms (1)
  • domain assumption Cores in a 7-core multicore fiber exhibit high mutual noise correlation sufficient for phase transfer
    Invoked in the first paragraph to justify using one core's phase information to stabilize another.

pith-pipeline@v0.9.0 · 5806 in / 1279 out tokens · 48943 ms · 2026-05-18T14:16:17.185025+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

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  1. Redefining the limits of real-time noise cancellation in optical fiber links

    physics.optics 2026-04 unverdicted novelty 6.0

    The conventional limit on real-time path-length noise suppression in optical fibers can be exceeded by optimizing the feedback signal with temporal correlations between round-trip and one-way signals, yielding 6 dB im...

Reference graph

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