Fig. 3: Dynamic control of quantum states.
From: All-optical modulation of quantum states by nonlinear metasurface
a Experimental setup for dynamic quantum state control. BBO: β-barium borate crystals; QC: quartz crystal; QWP: quarter-waveplate; HWP: half-waveplate; BS: beam splitter; PBS: polarized beam splitter; IF: interference filter; SMF: single-mode fiber. b The density matrix ρ of the initial state. The system has been biased to generate a non-maximally entangled state. The real part of ρ is given in the left column, and the imaginary part is shown on right. c The density matrix ρ of the distilled state after applying 14 mW control light. The initial state is redrawn here by dashed lines for a clear comparison. d The evolution of the quantum state as a function of the control light power (\(P_{{{\mathrm{C}}}}\)). Concurrence (top), fidelity (middle), and three characteristic elements of the density matrix (bottom) show the monotonic relationship with the power of the control light. Dots are experimental results, and lines are eye-guides
