Fig. 4: Experimental demonstration of PCQO algorithm.
From: Photonic counterdiabatic quantum optimization algorithm
a Schematic diagram for eight-qumode nanophotonic chip from Xanadu. The chip is divided into a pair of identical qumodes (0, 1, 2, 3) and (4, 5, 6, 7) utilizing S2(r) gate. This gate can be decomposed as a S(r) gate (S(r, ϕ = 0) in Table 1) with r = 0 or r = 1 and a \(BS\left(\frac{\pi }{4},0\right)\) gate as shown. Then, an arbitrary U4 unitary is applied to the pair followed by number-resolving measurements. b The PCQO ansatz considered for the experiment. This includes R(ϕ) gates applied to all the qumodes and BS(θ, 0) gates applied to nearest-neighbor connections. θ = {θ1, θ2, …} are optimizable parameters. c The mean photon number for all the qumodes obtained with the optimal circuit solving \(F({\bf{n}})={({n}_{0}+{n}_{2}-0.75)}^{2}\). The results shown are of a numerical simulation with D = 3 cutoff and the experiment with 1000 shots. The inset plot shows the mean photon number obtained by taking an average of the identical qumodes for both numerical simulation and experiment.
