Stabilizing Remote Entanglement via Waveguide Dissipation

Distributing entanglement between remote sites is integral to quantum networks. Here, we demonstrate the autonomous stabilization of remote entanglement between a pair of noninteracting superconducting qubits connected by an open waveguide on a chip. In this setting, the interplay between a classical continuous drive—supplied through the waveguide—and dissipation into the waveguide stabilizes the qubit pair in a dark state, which, asymptotically, takes the form of a Bell state. We use field-quadrature measurements of the photons emitted to the waveguide to perform quantum state tomography on the stabilized states, where we find a concurrence of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:msubsup><a:mn>0.504</a:mn><a:mrow><a:mo>−</a:mo><a:mn>0.029</a:mn></a:mrow><a:mrow><a:mo>+</a:mo><a:mn>0.007</a:mn></a:mrow></a:msubsup></a:math> in the optimal setting with a stabilization time constant of <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:mn>56</d:mn><d:mo>±</d:mo><d:mn>4</d:mn></d:math> ns. We examine the imperfections within our system and discuss avenues for enhancing fidelities and achieving scalability in future work. The decoherence-protected steady-state remote entanglement offered via dissipative stabilization may find applications in distributed quantum computing, sensing, and communication. Published by the American Physical Society 2024