arXiv subjects

Roman Goncharov

Publications and source records attributed to Roman Goncharov.

10 recordsLinked to original sources

arXiv2026

A theoretical study of subcarrier-wave quantum key distribution system integration with an optical transport network utilizing dense wavelength division multiplexing

In this paper we study the performance of subcarrier-wave quantum key distribution (SCW QKD) in the presence of classical channels of optical transport network utilizing dense wavelength division multiplexing (DWDM). We consider the impact of spontaneous Raman scattering noise as well as the four-wave mixing and channel isolation efficiency. We calculate quantum bit error rate as well as the secure key generation rate of SCW-QKD protocol for different parameters of DWDM system and quantum channel allocations. Our calculations show, that quantum channel allocation at the wavelength of 1310 nm is preferable to allocation at C-band due to lower nonlinear noise, despite fiber's larger attenuation at this wavelength.

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arXiv2026

Performance of the subcarrier-wave quantum key distribution in the presence of spontaneous Raman scattering noise generated by classical DWDM channels

In this paper we study performance of the subcarrier-wave quantum key distribution system (SCW QKD) in the presence of spontaneous Raman scattering (SpRS) noise generated by classical channels of dense wavelength division multiplexing (DWDM) network within a single-mode optical fiber. We present the mathematical model for evaluation of the quantum bit error rate (QBER) and the secure key generation rate with the SpRS noise taken into account. We consider two regimes of the SCW QKD system: the continuous wave regime that uses continuous wave laser and the pulsed regime. For these regimes, performance of the system is analyzed depending on receiver sensitivity of classical DWDM. It is found that the pulsed regime outperforms the continuous wave regime in both the secure key generation rate and the maximum achievable distance.

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arXiv2026

Iterative $C_Z$-gate-based protocol for squeezed Schr\"odinger cat state engineering

Squeezed optical Schr\"odinger cat states constitute a key resource for both fundamental tests of quantum theory and up-to-date quantum technologies. We propose a measurement-assisted gate for the generation and manipulation of the cat states. In this scheme, an ancilla in the non-Gaussian small-amplitude (in general, squeezed) Schr\"odinger cat state and the target oscillator initially prepared in a squeezed vacuum (or coherent) state are subjected to a quantum nondemolition (QND) entangling operation followed by projective homodyne measurement. The proposed gate enables generation of high-fidelity squeezed Schr\"odinger cat states with controllable size and squeezing with tunable fidelity/success-probability trade-off. We also introduce an iterative, homodyne-conditioned $C_Z$-based protocol for cat-state amplification. The parameter regimes required to achieve the desired fidelity and the success probability are analyzed. The approach is well suited for applications in measurement-based quantum computing and hybrid quantum networks where non-Gaussian resources enhance computational and communication capabilities.

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arXiv2025

Creation and manipulation of Schrödinger cat states based on semiclassical predictions

We consider the generation of Schr{ö}dinger cat states using a quantum measurement-induced logical gate where entanglement between the input state of the target oscillator and the Fock state of the ancillary system produced by the quantum non-demolition entangling $\hat{C}_Z$ operation is combined with the homodyne measurement. We utilize the semiclassical approach to construct both the input-output mapping of the field variables in the phase space and the wave function of the output state. This approach is found to predict that the state at the gate output can be represented by a minimally disturbed cat-like state which is a superposition of two copies of the initial state symmetrically displaced by momentum variable. For the target oscillator prepared in the coherent state, we show that the fidelity between the exact solution for the gate output state and the ``perfect'' Schr{ö}dinger cat reconstructed from the semiclassical theory can reach high values exceeding 0.99.

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arXiv2023

Quantum repeater via entangled phase modulated multimode coherent states

We present a scheme of quantum repeater that uses entangled multimode coherent states which are obtained by electro-optic modulation of symmetric and antisymmetric Schrödinger cat states. In this method subcarrier modes of the phase modulated states generated by the remote parties are sent to a symmetric beam splitter at the central node. The entangled coherent states are heraldedly prepared by photon counting measurements at the output channels of the beam splitter. We study how the effects of decoherence in the quantum channel affect statistics of photocounts and corresponding fidelity. We show how the proposed scheme can be useful for extending range of quantum key distribution with sub carrier wave encoding by exploiting quantum teleportation with the generated entanglement.

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arXiv2023

Theoretical analysis of quantum key distribution systems when integrated with a DWDM optical transport network

A theoretical research and numerical simulation of the noise influence caused by spontaneous Raman scattering, four-wave mixing, and linear channel crosstalk on the performance of QKD systems was conducted. Three types of QKD systems were considered: coherent one-way (COW) QKD protocol, subcarrier-wave (SCW) QKD system, and continuous-variable (CV) QKD integrated with classical DWDM channels. We calculate the secure key generation rate for the systems mentioned addressing different channel allocation schemes (i.e., configurations). A uniform DWDM grid is considered with quantum channel located in C-band and O-band (at 1310 nm) of a telecommunication window. The systems' performance is analyzed in terms of the maximal achievable distance values. Configurations for the further analysis and investigation are chosen optimally, i.e., their maximal achievable distances are the best.

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arXiv2023

Measurement-device-independent continuous variable quantum key distribution protocol operation in optical transport networks

Numerically, a theoretical analysis of the noise impact caused by spontaneous Raman scattering, four-wave mixing, and linear channel crosstalk on the measurement-device-independent continuous variable quantum key distribution systems is conducted. The analysis considers symmetry and asymmetry of system paths, as well as possible channel allocation schemes, for a quantum channel located in C- and O-bans. Mathematical models for MDI CV-QKD system and the contributing noises description are provided. The secure key generation rate is estimated to state features of protocol operation when integrated with existing DWDM systems in the context of its implementation into telecommunication networks.

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arXiv2022

Continuous-variable quantum key distribution: security analysis with trusted hardware noise against general attacks

In this paper, using the full security framework for continuous variable quantum key distribution (CV-QKD), we provide a composable security proof for the CV-QKD system in a realistic implementation. We take into account equipment losses and contributions from various components of excess noise and evaluate performance against collective and coherent attacks assuming trusted hardware noise. The calculation showed that the system remains operable at channel losses up to 10.2 dB in the presence of collective attacks and up to 7.5 dB in the presence of coherent ones.

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arXiv2020

Coherent detection schemes for subcarrier wave continuous variable quantum key distribution

We examine different methods to implement coherent detection in the subcarrier wave quantum key distribution (SCW QKD) systems. For classical wavefields, we present the models describing homodyne-type and heterodyne-type coherent detection schemes needed to extract information from the quadrature phase-coded multimode signals used in SCW QKD. Practical feasibility of the proposed schemes is corroborated by the experiments.

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arXiv2020

Subcarrier wave continuous variable quantum key distribution with discrete modulation: mathematical model and finite-key analysis

In this paper we report a continuous-variable quantum key distribution protocol using multimode coherent states generated on subcarrier frequencies of the optical spectrum. To detect the quadrature components of bosonic field we propose a coherent detection scheme where power from a carrier wave is used as a local oscillator. We compose a mathematical model of the proposed scheme and perform its security analysis in the finite-size regime using fully quantum asymptotic equipartition property technique. We calculate a lower bound on the secret key rate for the system under the assumption that the quantum channel noise is negligible compared to detector dark counts, and an eavesdropper is restricted to collective attacks. Our calculation shows that the current realistic system implementation would allow distributing secret keys over channels with losses up to 9 dB.

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