Probing coherence and noise tolerance in discrete-time quantum walks: unveiling self-focusing and breathing dynamics

• URL: http://arxiv.org/abs/2010.15281v1
• Date: Wed, 28 Oct 2020 23:37:59 GMT
• Title: Probing coherence and noise tolerance in discrete-time quantum walks: unveiling self-focusing and breathing dynamics
• Authors: A. R. C. Buarque and W.S. Dias
• Abstract summary: We study the consequences of a short-time (instantaneous) noise while an intensity-dependent phase acquisition is associated with a qubit propagating on $N-cycle. By employing quantum coherence measures, we report emerging unstable regimes in which hitherto unknown quantum walks arise.
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• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: The sensitivity of quantum systems to external disturbances is a fundamental problem for the implementation of functional quantum devices, quantum information and computation. Based on remarkable experimental progress in optics and ultra-cold gases, we study the consequences of a short-time (instantaneous) noise while an intensity-dependent phase acquisition is associated with a qubit propagating on $N$-cycle. By employing quantum coherence measures, we report emerging unstable regimes in which hitherto unknown quantum walks arise, such as self-focusing and breathing dynamics. Our results unveil appropriate settings which favor the stable regime, with the asymptotic distribution surviving for weak nonlinearities and disappearing in the thermodynamic limit with $1/N$. The diagram showing the threshold between different regimes reveals the quantum gates close to Pauli-Z as more noise-tolerant. As we move towards the Pauli-X quantum gate, such aptness dramatically decreases and the threshold to self-focusing regime becomes almost unavoidable. Quantum gates close to Hadamard exhibit an unusual aspect, in which an increment of the nonlinear strength can remove the dynamics from self-focusing regime.

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