Abstract: In a quantum network, coherent qubit nodes communicate with each other in an on-demand fashion through photonic links. Such networks may be an interesting path toward scaling highly coherent quantum systems, provided they can be interfaced efficiently with photonic interfaces. In a more fundamental direction, networks provide an intriguing platform for investigating limits for preserving distributed quantum states among weakly-interacting or non-interacting qubits.
Current research in our group is aimed at realizing different flavors of microwave quantum networks between superconducting qubits and cavities. Recently, we have implemented high-efficiency interconnects for such networks [1]. In this talk, I will focus on our efforts to use those interconnects for scaling superconducting quantum devices, and to investigate the possibility of stabilizing entanglement in open systems.
First, we are interested in networks as a scaling approach for high-coherence platforms. A bottleneck for such platforms is generally the choice of suitable nonlinearity for quantum state creation and detection. I will discuss our plans for combining high-Q cavities with the fluxonium qubit as high-coherence control and communication qubit. As a first step toward that end, we have investigated coupling a fluxonium to a linear storage resonator. We have investigated the nonlinearities in this system and used the fluxonium to create and readout quantum states in the resonator. Our results indicate that the fluxonium may be a promising alternative to the transmon for operating, manipulating, and connecting high-Q cavities.
Second, we ask whether it is possible to autonomously stabilize entanglement between effectively non-interacting qubits. To answer this question, we have realized a prototypical cascaded quantum network between separate superconducting qubit devices. Using local drives and nonreciprocal photon propagation, we have implemented a protocol that is predicted to generate driven-dissipative remote entanglement [2]. I will present experimental data that show evidence of entanglement stabilization. Additionally, I will discuss perspectives for extending our setup for high-fidelity entanglement delivery and autonomous distillation [3].
[1] M. Mollenhauer, et al., arXiv:2407.16743. Accepted in Nat. Electron.
[2] K. Stannigel, P. Rabl, and P. Zoller, New J. Phys. 14, 063014 (2012).
[3] A. Irfan, et al., Phys. Rev. Research 6, 033212 (2024).