TY - JOUR AB - AbstractThe nonorthogonality of coherent states is a fundamental property which prevents them from being perfectly and deterministically discriminated. Here, we present an experimentally feasible protocol for the probabilistic orthogonalisation of a pair of coherent states, independent of their amplitude and phase. In contrast to unambiguous state discrimination, a successful operation of our protocol is heralded without measuring the states. As such, they remain suitable for further manipulation and the obtained orthogonal states serve as a discretevariable basis. Therefore, our protocol doubles as a simple continuous-to-discrete variable converter, which may find application in hybrid continuous-discrete quantum information processing protocols. AU - Kruse, Regina AU - Silberhorn, Christine AU - Bartley, Tim ID - 16101 IS - 1 JF - Quantum Measurements and Quantum Metrology SN - 2299-114X TI - Heralded orthogonalisation of coherent states and their conversion to discrete-variable superpositions VL - 4 ER - TY - JOUR AB - AbstractQuantum mechanics establishes the ultimate limit to the scaling of the precision on any parameter, by identifying optimal probe states and measurements. While this paradigm is, at least in principle, adequate for the metrology of quantum channels involving the estimation of phase and loss parameters, we show that estimating the loss parameters associated with a quantum channel and a realistic quantum detector are fundamentally different. While Fock states are provably optimal for the former, we identify a crossover in the nature of the optimal probe state for estimating detector imperfections as a function of the loss parameter using Fisher information as a benchmark. We provide theoretical results for on-off and homodyne detectors, the most widely used detectors in quantum photonics technologies, when using Fock states and coherent states as probes. AU - Barbieri, Marco AU - Datta, Animesh AU - Bartley, Tim AU - Jin, Xian-Min AU - Kolthammer, W. Steven AU - Walmsley, Ian A. ID - 9836 JF - Quantum Measurements and Quantum Metrology SN - 2299-114X TI - Quantum enhanced estimation of optical detector efficiencies ER - TY - JOUR AU - Vidrighin, Mihai AU - Bartley, Tim AU - Donati, Gaia AU - Jin, Xian-Min AU - Barbieri, Marco AU - Kolthammer, W. Steven AU - Datta, Animesh AU - Walmsley, Ian A. ID - 16108 JF - Quantum Measurements and Quantum Metrology SN - 2299-114X TI - Requirements for two-source entanglement concentration ER -