Polarization-entangled frequency-domain cluster states using warm atomic vapor cell

Measurement-based quantum computer (MBQC) offers a practical route to universal quantum computation [1,2]. Frequency-mode cluster states, where multipartite entanglement is distributed across optical frequency bins, provide a scalable resource for MBQC. Recent experiments in warm atomic ensembles have demonstrated hypercubic frequency-domain cluster states by combining homodyne measurements of twin beams with electronic signal processing [3,4]. However, intensity-difference squeezing and quadrature squeezing in polarization modes parallel to the pump have not yet been reported.

Here we demonstrate polarization-entangled, frequency-domain cluster states generated in a warm ⁸⁵Rb atomic vapor cell by leveraging the atom’s intrinsic magnetic sublevels. By producing polarization-entangled two-mode squeezed vacuum (TMSV), we reconstruct the polarization correlations and verify cluster-state nullifiers. Our work opens a route to quantum networking between distributed high-dimensional cluster states and hybrid continuous-variable and discrete-variable systems.