Coupling of two distant spin ensembles via propagating continuum microwaves

Chong-Xin Run^1*, Kuan-Ting Lin², Kai-Min Hsieh¹, Bang-Yao Wu¹, Io-Chun Hoi¹

¹Department of Physics, City University of Hong Kong, Hong Kong SAR, China
²Department of Physics and Center for Quantum Science and Engineering, National Taiwan University, Taipei, Taiwan

* Presenter:Chong-Xin Run, email:cxrun2-c@my.cityu.edu.hk

We investigate the resonant dipole-dipole interaction (RDDI) between two distant spin ensembles coupled to a one-dimensional long coplanar waveguide (CPW). To probe the interaction, which arises from a summation over continuum modes of propagating microwaves, one end of the CPW is shorted to ground, functioning as a mirror. The reflection spectrum of the probe field is measured at the opposite end using a vector network analyzer (VNA). Experimental results reveal that when a spin ensemble is positioned at the node of the standing wave formed by incident and reflected waves, it exhibits significant interaction with a resonant spin ensemble located at an antinode, despite being theoretically decoupled from the field. In contrast to analogous experiments on other platforms, such as superconducting artificial atoms, our experimental system operates at room temperature, providing simplified fabrication and high flexibility. The spatial arrangement of the spin ensembles can be adjusted freely, with separations up to approximately 30 cm. Furthermore, we demonstrate coherent energy exchange between these two spin ensembles through time-domain measurements.

Keywords: Spin ensembles, Dipole-dipole interaction, Coplanar waveguide, Coherent energy exchange