Topologically Protected Quantum Entanglement Emitters

Entanglement and topology both portray nature at the fundamental level but in different manners. Entangled states of quantum particles are intrinsically sensitive to environment, whereas topological phases of matters represent natural robustness against environmental perturbations. Harnessing topology physics to protect entanglement thus has a great potential for reliable quantum applications. However, generating topologically-protected entanglement remains a significant challenge, which requires operating complex quantum devices in combined extreme conditions. Here we report topologically-protected quantum entanglement emitters, that emit topological Einstein-Podolsky-Rosen entangled state and topological multiphoton entangled state from a monolithically-integrated plug-and-play silicon-photonic chip in ambient conditions. The device emulating a photonic anomalous Floquet insulator allows the generation of up to four-photon topological entangled states at nontrivial edge modes. More importantly, we show that the Einstein-Podolsky-Rosen entanglement emitters can be topologically protected against artificial structure defects, by comparing tomographically measured fidelities of 0.968 ± 0.004 and 0.951 ± 0.01 for the perfect and defected emitters, respectively. Our topologically-protected entanglement emitters may find applications in photonic quantum computation and quantum simulation, and in the study of quantum topological physics.

Universal photonic quantum computation via time-delayed feedback

We propose and analyze a deterministic protocol to generate two-dimensional photonic cluster states using a single quantum emitter via time-delayed quantum feedback. As a physical implementation, we consider a single atom or atom-like system coupled to a 1D waveguide with a distant mirror, where guided photons represent the qubits, while the mirror allows the implementation of feedback. We identify the class of many-body quantum states that can be produced using this approach and characterize them in terms of 2D tensor network states.