Curator's Take
This fascinating experimental study reveals that the non-Hermitian skin effect, a quantum phenomenon that drives particles to accumulate at system boundaries, can actually survive and even be enhanced by certain types of noise and decoherence. The researchers used photonic quantum walks to demonstrate that while some decoherence mechanisms destroy this directional transport, others like dephasing can paradoxically make it stronger, challenging the conventional wisdom that quantum effects always degrade under environmental interference. This counterintuitive finding opens exciting possibilities for quantum devices that could exploit rather than merely tolerate noise, potentially leading to more robust quantum sensors and transport systems that work better in real-world conditions. The work bridges fundamental quantum physics with practical applications by showing how carefully engineered dissipation could become a resource rather than an obstacle in quantum technologies.
— Mark Eatherly
Summary
Decoherence and dissipation, arising from unavoidable interactions with the environment, can exert a dual influence on transport in physical systems, suppressing coherent propagation while inducing diffusion and mitigating localization in disordered systems. Non-Hermitian physics reveals a qualitatively different scenario, in which structured dissipation can induce directional bulk-to-boundary transport, known as the non-Hermitian skin effect (NHSE), that remains robust against disorder. Whether such transport can persist, be enhanced or hindered under decoherence, remains a largely open question. Here we experimentally address this question using photonic quantum walks with two tunable prototypical decoherence channels, dephasing and amplitude damping. Under dephasing, the NHSE survives up to the fully incoherent regime and is observed to even be enhanced by dephasing, yielding drift velocities that exceed those of coherent dynamics. By contrast, amplitude damping shows a pronounced order dependence: applied before the non-Hermitian loss operator, it suppresses and ultimately eliminates the NHSE in the fully incoherent limit; applied afterward, the NHSE persists and can be enhanced at sufficiently large loss strengths. Our work bridges quantum and classical non-Hermitian dynamics, demonstrates the resilience of the NHSE to decoherence, and opens avenues for harnessing decoherence to enhance directional transport in noisy, nonequilibrium systems.