Multimode entanglement is an essential resource for quantum information processing and quantum metrology. However, multimode entangled states are generally constructed by targeting a specific graph configuration. This yields to a fixed experimental setup that therefore exhibits reduced versatility and scalability. Here we demonstrate an optical on-demand, reconfigurable multimode entangled state, using an intrinsically multimode quantum resource and a homodyne detection apparatus. Without altering either the initial squeezing source or experimental architecture, we realize the construction of thirteen cluster states of various sizes and connectivities as well as the implementation of a secret sharing protocol. In particular, this system enables the interrogation of quantum correlations and fluctuations for any multimode Gaussian state. This initiates an avenue for implementing on-demand quantum information processing by only adapting the measurement process and not the experimental layout.

Figure | Multimode quantum resource. (a,b) 16-partite covariance matrix in the frequency-pixel basis in phase and amplitude quadrature, rexpectively.This correlation matrix is obtained with balanced homodyne detection where the spectrum of the local oscillator is divided into 16 frequency bands of equivalent width. The shot noise contribution has been subtracted from the diagonal for increased visibility, and axis values are normalized to vacuum noise. (c) Inferred squeezing of the eigenmodes (corrected/not corrected from measurement losses). The ellipses (blue) represent the squeezing of the twelve leading modes. The circles (red) represent vacuum fluctuations for comparison. Twelve of the sixteen modes are squeezed. The measurement results in panels a–c have been corrected for electrical dark noise and a 15% optical loss in the measurement processes.

Multimode entanglement in reconfigurable graph states using optical frequency combs.pdf