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arXiv:2610.39657

Detection and Inhibition of Decoherence Through Collisions: A dynamical approach

Sagnik Chakraborty, Srijon Ghosh, Federico Amato, Gniewomir Sarbicki, Dariusz Chruściński, Rosario Lo Franco

quant-phSubmitted Oct 29, 2026• Announced Oct 30, 2026• 0 citations
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Abstract

Quantum systems are intrinsically fragile and highly vulnerable to environmental noise, making the preservation of quantum states one of the fundamental challenges in realizing practical quantum technologies. We propose two noise-agnostic quantum state protection protocols based on a collisional model. The first protocol preserves quantum states of qubits without requiring complete prior knowledge of the underlying noise dynamics, and the second even protects a logical qubit under similar circumstances. These protocols provide robust protection for arbitrary single-qubit and entangled states against general noise processes. Furthermore, their capability to safeguard quantum states with an arbitrary number of qubits enhances the reliability, robustness, and scalability of emerging quantum architectures. These results establish the proposed framework as a promising approach for practical quantum information processing.

AI Summary

The paper studies adaptive state protection when the applied channel is unknown but belongs to a known pair $\{\Omega_1,\Omega_2\}$ with known prior probabilities. It combines noise discrimination and Petz recovery in a collisional model: a detection ancilla interacts with the system and is measured using a minimum-error discrimination measurement; a second ancilla implements the selected recovery map through a Stinespring dilation. Recovery selection follows the majority of accumulated measurement outcomes. For a known target state, the Petz map uses that state as its reference. Numerical examples cover single-qubit amplitude damping, dephasing, bit-flip and randomly generated channels, together with mixed GHZ states of two to four qubits. The reported single-qubit infidelity reaches approximately $10^{-9}$ after repeated cycles, although incorrect channel selections can cause transient increases. These results concern target-dependent recovery, rather than a common recovery operation for unknown input states. A separate protocol protects states in the repetition-code subspace $\mathcal C=\operatorname{span}\{|0\rangle^{\otimes N},|1\rangle^{\otimes N}\}$ against independent bit-flip noise. It uses a thermal reference state, weak measurements and short detection interactions. Simulations averaging over 100 Haar-random logical states report one-cycle average infidelity around $10^{-2}$ for $N=5$. With two candidate noise strengths, repeated recovery maintains fidelity above 80% initially and later approaches approximately 65%. The paper identifies measurement disturbance, longer detection interactions and greater differences between candidate noise strengths as limitations for logical-state recovery. Evidence is numerical; the construction assumes access to tailored recovery unitaries.

Little sign of AI-generated textOverclaimsStrong assumptionsMissing comparisonPossible error

Central claim may not hold: The demonstrated scope is narrower than the broad protection claims: individual-state recovery requires the known target and two known candidate channels, while logical-qubit tests cover only independent bit-flip noise. The small-system examples do not establish a general guarantee of scalable protection of encoded quantum information. The stated fidelity equals Tr(rho_ini rho_reco), which gives purity rather than unity at perfect recovery of a mixed target. The specified higher-dimensional replacement-channel construction makes its Petz recovery prepare the reference state, limiting logical-state fidelity to at most one half for the stated thermal reference and contradicting the reported logical fidelities. The weak-measurement outcome probabilities and conditional state updates do not describe the same quantum measurement instrument.

Written by gpt-6.1-sol from the paper's full text. Automated: it can be wrong.

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9 pages, 6 figures

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Quantum systems are intrinsically fragile and highly vulnerable to environmental noise, making the preservation of quantum states one of the fundamental challenges in realizing practical quantum technologies. We propose two noise-agnostic quantum state protection protocols based on a collisional model. The first protocol preserves quantum states of qubits without requiring complete prior knowledge of the underlying noise dynamics, and the second even protects a logical qubit under similar circumstances. These protocols provide robust protection for arbitrary single-qubit and entangled states against general noise processes. Furthermore, their capability to safeguard quantum states with an arbitrary number of qubits enhances the reliability, robustness, and scalability of emerging quantum architectures. These results establish the proposed framework as a promising approach for practical quantum information processing.
The paper studies adaptive state protection when the applied channel is unknown but belongs to a known pair {Ω1,Ω2}\{\Omega_1,\Omega_2\}{Ω1​,Ω2​} with known prior probabilities. It combines noise discrimination and Petz recovery in a collisional model: a detection ancilla interacts with the system and is measured using a minimum-error discrimination measurement; a second ancilla implements the selected recovery map through a Stinespring dilation. Recovery selection follows the majority of accumulated measurement outcomes.
For a known target state, the Petz map uses that state as its reference. Numerical examples cover single-qubit amplitude damping, dephasing, bit-flip and randomly generated channels, together with mixed GHZ states of two to four qubits. The reported single-qubit infidelity reaches approximately 10−910^{-9}10−9 after repeated cycles, although incorrect channel selections can cause transient increases. These results concern target-dependent recovery, rather than a common recovery operation for unknown input states.
A separate protocol protects states in the repetition-code subspace C=span⁡{∣0⟩⊗N,∣1⟩⊗N}\mathcal C=\operatorname{span}\{|0\rangle^{\otimes N},|1\rangle^{\otimes N}\}C=span{∣0⟩⊗N,∣1⟩⊗N} against independent bit-flip noise. It uses a thermal reference state, weak measurements and short detection interactions. Simulations averaging over 100 Haar-random logical states report one-cycle average infidelity around 10−210^{-2}10−2 for N=5N=5N=5. With two candidate noise strengths, repeated recovery maintains fidelity above 80% initially and later approaches approximately 65%.
The paper identifies measurement disturbance, longer detection interactions and greater differences between candidate noise strengths as limitations for logical-state recovery. Evidence is numerical; the construction assumes access to tailored recovery unitaries.
The fragility of quantum coherence fundamentally limits the scalability of quantum technologies, as unavoidable environmental interactions induce decoherence and rapidly degrade quantum properties. The Quantum Zeno Effect offers a powerful route to suppress quantum evolution and protect coherence through frequent measurements, irrespective of the underlying dynamics. However, existing implementations require prior knowledge of the quantum state, severely restricting their applicability. Here we introduce a state- and dynamics-independent protection protocol embedding the system in a larger Hilbert space, temporarily swapping the quantum information from its original degree of freedom to a decoherence-free ancillary one. We experimentally validate the protocol on a quantum optical platform, demonstrating robust preservation of coherence and purity for arbitrary polarization qubits under decoherence, thereby enabling the universal safeguarding of unknown quantum states.
Mitigating noise-induced decoherence is the central challenge in controlling open quantum systems. While existing robust protocols often require precise noise models, we introduce a universal framework for noise-agnostic quantum control that achieves high-fidelity operations without prior environmental noise characterization. This framework capitalizes on the dynamical modification of the system-environment coupling through control drives, an effect rigorously encoded in the dynamical equation. Since the derived noise sensitivity metric remains independent of the coupling details between the system and the environment, our protocol demonstrates robustness against arbitrary Markovian noises within the first-order weak coupling approximation. Numerical validation through quantum state transfer and gate operations reveals near-unity fidelity across diverse noise regimes, achieving orders-of-magnitude error suppression compared to target-only approaches. This framework bridges critical gaps between theoretical control design and experimental constraints, establishing a broadly applicable strategy for high-fidelity quantum information processing across platforms such as superconducting circuits, trapped ions, and solid-state qubits.
Quantum decoherence represents a significant hurdle in the development of practical quantum computers. The inherent fragility of quantum states makes them susceptible to environmental noise, leading to rapid loss of quantum information. This work explores a novel approach to mitigating decoherence by leveraging the principles of topological protection. We propose constructing a quantum bit (qubit) array utilizing a topologically protected architecture. This design aims to isolate qubits from unwanted interactions, thereby significantly reducing the detrimental effects of decoherence. The core mechanism relies on the robust nature of topological invariants, which shield the quantum states from local perturbations. This approach offers a promising pathway toward enhancing the coherence times of qubits and ultimately improving the reliability of quantum computation. The theoretical framework presented here outlines the design considerations and potential advantages of this strategy.
Quantum decoherence poses a significant challenge to the development of practical quantum computers. The inherent sensitivity of quantum states to environmental interactions leads to rapid loss of quantum information. This work proposes a novel strategy for mitigating decoherence effects by leveraging topological protection. Specifically, we investigate the construction of quantum device arrays utilizing topologically protected states, combined with non-Abelian entanglement, to create a robust barrier against external noise. The core concept relies on isolating quantum bits (qubits) from environmental interactions through the unique properties of topological insulators and engineered topological structures. This approach aims to dramatically improve the fidelity and stability of quantum computations. Mathematical formulations detail the theoretical framework, demonstrating the potential of this method to achieve significantly reduced decoherence rates and enhanced quantum coherence times. The proposed architecture offers a pathway toward building more reliable and scalable quantum computing platforms.
We propose and analyze a robust quantum-state transfer protocol by the use of a combination of coherent quantum coupling and decoherence-free subspaces in a coupled quantum spin chain. Under decoherence, an arbitrary unknown quantum state embedded in a decoherence-free subspace can be perfectly transferred through a noisy channel being weakly coupled to two end registers. The method protects quantum information from both the channel noise and the environmental decoherence. A special case of utilizing two physical qubits to encode one logical qubit is considered as an example and the robustness is confirmed by numerical performances.
This paper investigates the potential of utilizing quantum decoherence as a foundation for enhanced computational security. Traditional cryptographic algorithms are increasingly vulnerable to attacks leveraging quantum computing capabilities. This research proposes a novel approach to secure key distribution by exploiting the inherent properties of quantum decoherence. We design a quantum key distribution (QKD) protocol that incorporates controlled quantum noise and environmental interactions, specifically leveraging the rapid decoherence of quantum states. The protocol's core principle is that the unpredictable nature of decoherence – the loss of quantum information due to interaction with the environment – makes it extraordinarily difficult for an eavesdropper to predict and exploit the key distribution process. The resulting security stems not from the laws of physics themselves, but from the attacker's inability to reliably model and manipulate the quantum system's rapidly evolving state. We present a mathematical framework to analyze the security of this protocol, highlighting key parameters influencing its resilience. This work offers a fundamentally new security paradigm, shifting the focus from algorithm-based security to a system-level approach centered around harnessing the chaotic nature of quantum decoherence. The presented scheme demonstrates a promising path toward building robust, quantum-resistant cryptographic systems.