Sichuan University team finds noise may boost defects via ‘stochastic resonance’

A new capability exists for understanding key dynamics: distinctions can now be made between Gaussian and non-Gaussian noises within quantum systems. The work focuses on dichotomous Markov noise, a common type of fluctuation found in real materials, revealing that its impact on defect density behaves differently than traditional Gaussian coloured noise. Specifically, defects initially increase then decrease with changing correlation time, an effect termed generalised stochastic resonance not seen with standard noise models.

The research reveals a fundamental difference between Gaussian and non-Gaussian noises affecting quantum systems undergoing rapid change. Researchers at Sichuan University have uncovered a surprising difference in how quantum systems respond to different types of electronic ‘noise’, random fluctuations that disrupt delicate processes. While standard Gaussian noise consistently increases defects in these materials as fluctuations slow down, dichotomous Markov noise, a common type of fluctuation, initially *increases* defect formation but then reduces it; this is termed generalised stochastic resonance.

Traditional Gaussian noise consistently increases defects within materials as these fluctuations slow down, while a specific type called dichotomous Markov noise (DMN) behaves differently, imagine flipping a coin repeatedly and rapidly, it’s randomly “on” or “off”, unlike static sounds. The team believes this is due to the way DMN creates sparse events, like throwing darts and hitting only a few spots on the board despite many attempts, which contrasts with how standard noise affects imperfections during rapid changes in a system akin to quickly stretching a rubber band.

Dichotomous Noise Reveals Nonmonotonic Defect Formation via Generalised Stochastic Resonance

This breakthrough unlocks analysis previously impossible due to limitations capturing sparse realizations of non-Gaussian noise, allowing detailed examination of anti-Kibble-Zurek behaviour where slower transitions unexpectedly produce fewer defects than predicted.

Dichotomous Markov noise, a fluctuating signal switching randomly between states, can induce anti-Kibble-Zurek behaviour within a quantum Ising chain, resulting in a nonmonotonic change in defect density as fluctuation speed varies. The number of noise-induced defects initially grows and then decreases alongside changes to the correlation time.

Unlike Gaussian coloured noise which shows monotonic variation, the contribution of dichotomous Markov noise scales differently depending on how quickly fluctuations occur, demonstrating that detailed statistical properties are important beyond just examining the power spectrum. Correlation time plays distinct roles for rapid versus slow noise, driving generalised stochastic resonance.

Generalised Stochastic Resonance Reveals Nonmonotonic Defect Behaviour in Quantum Magnetism

The researchers acknowledge their work remains confined to a specific scenario: the quantum Ising chain; however, understanding how noise impacts quantum systems is vital for building stable technologies reliant on delicate phase transitions. This limitation begs whether this newly observed generalised stochastic resonance extends beyond magnetism into other areas of physics and materials science. Despite its focus on the Ising chain, understanding how different types of noise affect such systems is fundamental to building robust quantum technologies.

Unpredictable ‘dichotomous noise’ has been revealed as impacting quantum systems differently than smoother variations, potentially unlocking new strategies for durable devices and prompting a fresh look at material behaviour under stress. The Sichuan University team demonstrated that dichotomous Markov noise induces generalised stochastic resonance in these systems; defect formation initially increases then decreases as fluctuation speed changes. This contrasts with standard Gaussian noise which consistently creates more defects at slower rates, revealing fundamental differences in how non-Gaussian and Gaussian noises affect imperfections during rapid transitions. By focusing on sparse realizations rather than solely the power spectrum of this noise, they uncovered anomalous anti-Kibble-Zurek behaviour previously hidden within complex dynamics.

Researchers found that dichotomous Markov noise, a specific type of unpredictable fluctuation, affected a quantum Ising chain differently from smoother, Gaussian noise. Specifically, the team observed generalized stochastic resonance where the creation of defects first increased and then decreased depending on the speed of these fluctuations; this is unlike Gaussian noise which consistently produces more defects at slower rates.

This work highlights that detailed statistical properties beyond just overall signal strength are important when considering how noise impacts systems undergoing rapid change. The findings reveal fundamental distinctions between Gaussian and non-Gaussian noises in critical quench dynamics, offering new insight into nonequilibrium processes within quantum magnetism.

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