"P(ED2.1.00/03.0058), P(EE2.3.20.0017), P(EE2.3.20.0058), P(EE2.3.30.0041), P(GP13-31000P)" . . . . "2"^^ . "88" . "Lemr, Karel" . . . "Bartkiewicz, Karol" . "RIV/61989592:15310/13:33146337!RIV14-GA0-15310___" . . "http://pra.aps.org/pdf/PRA/v88/i5/e052104" . . . . "69793" . . . "Direct method for measuring of purity, superfidelity, and subfidelity of photonic two-qubit mixed states" . . "5" . "10.1103/PhysRevA.88.052104" . . . . "The Uhlmann-Jozsa fidelity (or, equivalently, the Bures distance) is a basic concept of quantum communication and quantum information, which however is very difficult to measure efficiently without recourse to quantum tomography. Here we propose a direct experimental method to estimate the fidelity between two unknown two-qubit mixed states via the measurement of the upper and lower bounds of the fidelity, which are referred to as the superfidelity and subfidelity, respectively. Our method enables a direct measurement of the first- and second-order overlaps between two arbitrary two-qubit states. In particular, the method can be applied to measure the purity (or linear entropy) of a single two-qubit mixed state in a direct experiment. We also propose and critically compare several experimental strategies for measuring the sub- and superfidelities of polarization states of photons in various linear-optical setups."@en . . "photonic two-qubit, quantum communication, quantum information, superfidelity, subfidelity"@en . "RIV/61989592:15310/13:33146337" . "Miranowicz, Adam" . "The Uhlmann-Jozsa fidelity (or, equivalently, the Bures distance) is a basic concept of quantum communication and quantum information, which however is very difficult to measure efficiently without recourse to quantum tomography. Here we propose a direct experimental method to estimate the fidelity between two unknown two-qubit mixed states via the measurement of the upper and lower bounds of the fidelity, which are referred to as the superfidelity and subfidelity, respectively. Our method enables a direct measurement of the first- and second-order overlaps between two arbitrary two-qubit states. In particular, the method can be applied to measure the purity (or linear entropy) of a single two-qubit mixed state in a direct experiment. We also propose and critically compare several experimental strategies for measuring the sub- and superfidelities of polarization states of photons in various linear-optical setups." . . . . "Bartkiewicz, Karol" . "Direct method for measuring of purity, superfidelity, and subfidelity of photonic two-qubit mixed states"@en . "Physical Review A" . "15310" . "8"^^ . "[95A4F6379B6A]" . "000326815800001" . "1050-2947" . "3"^^ . "Direct method for measuring of purity, superfidelity, and subfidelity of photonic two-qubit mixed states"@en . "Direct method for measuring of purity, superfidelity, and subfidelity of photonic two-qubit mixed states" . . . . "US - Spojen\u00E9 st\u00E1ty americk\u00E9" .