Although it has been known for some time that quantum mechanics can be formulated in a way that treats prediction and retrodiction on an equal footing, most attention in engineering quantum states has been devoted to predictive states, that is, states associated with a preparation event. Retrodictive states, which are associated with a measurement event and propagate backwards in time, are also...

We discuss a novel method of efficiently producing multiphoton states using repeated spontaneous parametric down-conversion. Specifically, by attempting down-conversion several times, we can pseudodeterministically add photons to a mode, producing various several-photon states, e.g., Fock states and N00N states (number-path entangled states of the form |N(A), 0(B)>+|0(A), N(B)>). This scheme is...

Li-Min Lee, Shan-Chuang Pei, Der-Fong Lin, Po-Chun Chiu, Mon-Chang Tsai, Ta-Min Tai, De-Hao Sun, A. H. Kung, and Sheng-Lung Huang* Institute of Electro-Optical Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan Department of Electrical Engineering, Yung Ta Institute of Technology & Commerce, Pingtung 909, Taiwan Graduate Institute of Electro-Optical Engineering, National Taiwan...