When quantum resources backfire: Non-gaussianity and symplectic coherence in noisy bosonic circuits

2025-10-08

AI Summary

This work investigates how noise affects the classical simulability of continuous-variable (bosonic) quantum circuits, revealing that typical quantum resources—such as non-Gaussianity and symplectic coherence—paradoxically enhance classical simulability under noise, giving rise to a “quantum-resource backfire” phenomenon and multiple computational phase transitions. Method: We introduce the displacement propagation algorithm—the first efficient classical simulation method for noisy bosonic circuits—inspired by Pauli propagation in discrete-variable systems but adapted to the symplectic structure of continuous variables and realistic noise channels. Contribution/Results: The algorithm demonstrates that moderate noise suffices to suppress quantum advantage in circuits relying on non-Gaussian operations and coherence resources, challenging the conventional “more resources imply greater advantage” paradigm. Our findings establish new criteria and tools for assessing the practical feasibility of bosonic quantum computation.

Technology Category

• Machine Learning: Quantum Machine Learning
• Search and Optimization: Mixed Discrete/Continuous Search
• Constraint Satisfaction and Optimization: Mixed Discrete/Continuous Optimization

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Fairness, privacy, and diversity in economic environments
• Graph Algorithms and Modeling for the Web: Algorithms and analysis for incomplete, noisy, or partially observed Web-related graphs

Abstract

Analyzing the impact of noise is of fundamental importance to understand the advantages provided by quantum systems. While the classical simulability of noisy discrete-variable systems is increasingly well understood, noisy bosonic circuits are more challenging to simulate and analyze. Here, we address this gap by introducing the $ extit{displacement propagation}$ algorithm, a continuous-variable analogue of Pauli propagation for simulating noisy bosonic circuits. By exploring the interplay of noise and quantum resources, we identify several computational phase transitions, revealing regimes where even modest noise levels render bosonic circuits efficiently classically simulable. In particular, our analysis reveals a surprising phenomenon: computational resources usually associated with bosonic quantum advantage, namely non-Gaussianity and symplectic coherence, can make the system easier to classically simulate in presence of noise.

Problem

• Develops algorithm to simulate noisy bosonic quantum circuits efficiently
• Identifies computational transitions where noise enables classical simulation
• Reveals quantum resources can backfire under noise conditions

Innovation

• Developed displacement propagation algorithm for simulation
• Identified computational phase transitions in noisy circuits
• Revealed non-Gaussianity simplifies classical simulation with noise