title: Experimental investigation of a nonideal two-qubit quantum-state filter by quantum process tomography.
abstract: We used quantum process tomography to investigate and identify the function of a nonideal two-qubit quantum-state filter subject to various degrees of decoherence. We present a simple decoherence model that explains the experimental results and point out that a beam splitter followed by a postselection process is not, as commonly believed, a singlet-state filter. In the ideal case it is a triplet-state filter.
authors.affiliation: Fundamental and Environmental Research Laboratories, NEC, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nambu
authors.forename: Kazuo
authors.initials: K
authors.lastname: Nakamura