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Journal of Modern Optics

Quantum-classical interaction noise and mitigation in shared optical fibre system

Harish Parthasarathy, Yogesh Kashyap, Nidarshana, Parul Garg, Anand Kumar Srivastava, Dushyant Kumar

Published Feb 14, 2026• 0 citations
Publisher

Abstract

Scalability in quantum networks requires the co-propagation of quantum and classical signals within shared optical fibres. However, classical fields interact with thermally induced atomic vibrations (phonons), generating scattering and noise that degrade quantum information. We model this interaction using a random Hamiltonian and the Lindblad master equation, accounting for both deterministic and stochastic noise components. To mitigate these effects, we propose a novel control method that introduces a counter-potential to cancel the average interaction noise. Simulations indicate a significant reduction in the noise-to-signal energy ratio using this approach. Additionally, we analyse a fully quantized scenario involving quantum phonon lattices and noise. We outline a method for generating counter-TPCP (Trace-Preserving Completely Positive) maps to neutralize these interactions. Finally, we provide a Monte Carlo algorithm, based on the LucBouten method, to construct these counter maps using a random potential. This research fosters robust, high-efficiency quantum technology development.

DOI
10.1080/09500340.2026.2628815

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Scalability in quantum networks requires the co-propagation of quantum and classical signals within shared optical fibres. However, classical fields interact with thermally induced atomic vibrations (phonons), generating scattering and noise that degrade quantum information. We model this interaction using a random Hamiltonian and the Lindblad master equation, accounting for both deterministic and stochastic noise components. To mitigate these effects, we propose a novel control method that introduces a counter-potential to cancel the average interaction noise. Simulations indicate a significant reduction in the noise-to-signal energy ratio using this approach. Additionally, we analyse a fully quantized scenario involving quantum phonon lattices and noise. We outline a method for generating counter-TPCP (Trace-Preserving Completely Positive) maps to neutralize these interactions. Finally, we provide a Monte Carlo algorithm, based on the LucBouten method, to construct these counter maps using a random potential. This research fosters robust, high-efficiency quantum technology development.
We consider the propagation of the electromagnetic field within an optical fibre. The field consists of a classical component and a quantum component. The classical component is large and it interacts with the matter within the fibre comprising of atoms that are vibrating, ie, phonons. This interaction causes scattering of the classical field component that interacts with the quantum component of the field, thereby altering the state of the quantum field. After constructing this model, we propose two methods for reducing this "classical-photon-phonon interaction noise". The first method is based on an optimal control algorithm wherein we generate a "control potential" in such a way that after incorporating this potential in the Schrodinger dynamics of the state the state tracks as closely as possible a desired "noiseless state". The second approach is based on Belavkin’s quantum filtering theory wherein we model the classical photons as a quantum Bosonic white noise process and by taking non-demolition measurements on the system, we generate on a real-time basis, an estimate of the evolving state which by application of a control potential is made to track a desired state. Analysis of the spectrum of the transmitted quantum electromagnetic field is carried out by using a quantum stochastic differential model for the noise based on the Hudson-Parthasarathy quantum stochastic calculus. Further, the basic ideas of Cq channel capacities in quantum information theory are used to analyze the rate of information transmission through this optical fibre quantum mechanical channel. Transmission of other kinds of particles like non-Abelian matter and gauge particles are also discussed and the role of superstring theory in building a foundation for corrections to the Yang-Mills action is also discussed. We also highlight the use of the quantum effective action of a field when it interacts with other fields and with random current sources. The quantum effective action, obtained using Feynman’s path integral methods for fields provides a firm foundation for corrections to the classical action by quantum effects and enables one to describe the quantum corrections to the field equations accurately.
The rising interest in quantum-level communication has resulted in proposals for coexistence schemes with classical signals within the same fiber optic channel, where the most recent proposals leverage novel fibers designed for space-division multiplexing (SDM) transmission. In all cases the large power difference between classical and quantum channels presents challenges for such schemes, as the classical signals generate interfering noise that corrupts the quantum signal. In this work, we discuss the main interference mechanisms in coexistence scenarios and provide a model to quantify their impact on the quantum signal quality. Analytical approximations in the model allow accurate and fast numerical solutions in the millisecond time-scale. The model accounts for out-of-band non-linear interference effects, namely spontaneous Raman scattering (SpRS) and four-wave-mixing (FWM) in both cases of single-mode and SDM fibers with weakly-coupled degenerate mode groups. Rayleigh and SpRS backscattering are considered in counter-propagating scenarios. Since broadband classical transmission is targeted, the model also accounts for the effect of stimulated Raman scattering (SRS)-induced power tilt. Use of the model in sample scenarios indicates that the interference noise power is minimized at the high end of the transmission band in both cases were the quantum is co- and counter-propagating with respect to the classical signals, with a preference of one or the other scheme depending on the link length and quantum signal center frequency. Our model reveals that FWM has negligible impact in counter-propagating schemes, but can be relevant in co-propagating schemes under certain scenarios. Nevertheless, the FWM interference can be mitigated by deallocating the classical signals adjacent to the quantum channel.
Analogue quantum simulators offer a promising route to explore quantum many-body dynamics beyond classical reach in the near term. However, their vulnerability to noise limits the accuracy of simulations. Here, we establish a new framework for mitigating noise in analogue quantum simulation, operating in a time-continuous manner. To our knowledge, this is the first protocol that is fully analogue and that achieves exact noise cancellation. Our method requires a small number of ancillary qubits, whose interaction with the system−-−combined with classical post-processing of joint measurement data−-−is tailored to cancel the effect of noise. Furthermore, the protocol is Hamiltonian-independent, robust to realistic ancilla noise, and avoids any discretization, preserving the continuous-time nature of the system's dynamics. This work opens a new direction for achieving high-fidelity analogue quantum simulation in the presence of noise.
We analyze the quantum dynamics of radiation propagating in a single-mode optical fibre with dispersion, nonlinearity, and Raman coupling to thermal phonons. We start from a fundamental Hamiltonian that includes the principal known nonlinear effects and quantum-noise sources, including linear gain and loss. Both Markovian and frequency-dependent, non-Markovian reservoirs are treated. This treatment allows quantum Langevin equations, which have a classical form except for additional quantum-noise terms, to be calculated. In practical calculations, it is more useful to transform to Wigner or +P quasi-probability operator representations. These transformations result in stochastic equations that can be analyzed by use of perturbation theory or exact numerical techniques. The results have applications to fibre-optics communications, networking, and sensor technology.
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Abstract All quantum systems are subject to noise and imperfections due to stray fields, inhomogeneities or drifting experimental controls. An understanding of the effects of noise and decoherence is critical to the progress towards fully functional quantum devices. In this perspective, we focus on noise in quantum systems which are modelled by a dynamic stochastic parameter in the Hamiltonian. We will outline exact evolution equations describing the ensemble average dynamics for a variety of common noise types and their connections. We will also highlight an approximate evolution equation valid in the weak noise limit for an arbitrary classical stochastic field. This framework should serve as a starting point for identifying signatures of differing noise types and optimisation of robust control protocols.