Endurance of quantum coherence due to particle indistinguishability in noisy quantum networks.

Quantum coherence, the physical property underlying fundamental phenomena such as multi-particle interference and entanglement, has emerged as a valuable resource upon which modern technologies are founded. In general, the most prominent adversary of quantum coherence is noise arising from the interaction of the associated dynamical system with its environment. Under certain conditions, however, the existence of noise may drive quantum and classical systems to endure intriguing nontrivial effects. In this vein, here we demonstrate, both theoretically and experimentally, that when two indistinguishable non-interacting particles co-propagate through quantum networks affected by non-dissipative noise, the system always evolves into a steady state in which coherences accounting for particle indistinguishabilty perpetually prevail. Furthermore, we show that the same steady state with surviving quantum coherences is reached even when the initial state exhibits classical correlations. Quantum physics: multi-particle coherence cuts through the noise The coherence between identical quantum particles in contact with the environment can be preserved due to the particles' indistinguishability. Usually coherence is destroyed when a quantum system is in contact with the environment as part of the crossover between microscopic quantum effects and the macroscopic classical world. However, sometimes quantum coherence persists even in contact with an environment. A team led by Alexander Szameit from Universität Rostock have shown theoretically and experimentally that the quantum properties of identical particles realizes one such scenario. When a system has multiple indistinguishable particles, the wavefunction must be symmetric or antisymmetric under exchange of particles. Szameit et al. demonstrate that, even in a device where a single particle is decohered by the environment, the additional correlations required by indistinguishability counter-intuitively lead to multi-particle steady states that preserve quantum coherence. [ABSTRACT FROM AUTHOR]