Fig. 1. Experimental setup. (a) Single-photon source preparation; (b) three parts are initial state preparation, evolution, and final state measurement from left to right in sequence

Fig. 2. Final state density matrix theoretical value

Fig. 3. Final state density matrix experimental value from quantum state tomography

Fig. 4. Experimental observation of the breaking of the PT-symmetry (real part of eigenvalue E₊ decreases when 0<a<1 and equals zero when a>1)

Fig. 5. Experimental observation of the breaking of the PT-symmetry (imaginary part of eigenvalue E₊ equals zero when 0<a<1 and increases when a>1)