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Full characterization of detectors in the quantum regime is presented. We determine the POVM elements of a photon-number-resolving detector. A method for precise calibration of detector efficiency is demonstrated.
In this work, the fabrication of direct UV writing (DUVW) structures, compact couplers appropriate for quantum optical circuits is reported, and the use of X-couplers for a more compact device layout with improved fibre compatibility, v-groove launch, and polarisation control is discussed. These devices are well suited to quantum interference applications.
The paper reports the proof-of-principle experimental quantum-enhanced phase estimation. The measurement is based on specifically designed two-photon states that maximize the amount of information about the detected phase in the presence of loss.
We experimentally demonstrate photon pair production in standard single-mode optical fibers via spontaneous four-wave mixing. The process utilizes birefringent phase matching to control the photon pair joint spectral structure.
We present the joint photon-number statistics of a locally photon-subtracted two-mode vacuum squeezed state of light. Comparison to the unsubtracted statistics shows a successful photon subtraction and the expected shift by one photon number.
We present the first quantum tomography of a detector, using as examples an avalanche photodiode and a photon-number resolving detector. The resulting POVM set agrees well with one derived from a model of the detector.
We introduce a complete tomographic reconstruction scheme geared toward low photon-number states. To demonstrate this method we reconstruct various single-mode coherent states.
Weak measurements are a new tool for characterizing post-selected quantum systems during their evolution. Weak measurement was originally formulated in terms of von Neumann interactions which are practically available for only the simplest single-particle observables. In the present work, we extend and greatly simplify a recent, experimentally feasible, reformulation of weak measurement for multiparticle...
The three-box problem is a gedankenexperiment designed to elucidate some interesting features of quantum measurement and locality. A particle is prepared in a particular superposition of three boxes, and later found in a different (but nonorthogonal) superposition. It was predicted that appropriate ''weak'' measurements of particle position in the interval between preparation and post-selection would...
We present recent experiments on production of entangled states using linear optical elements and post-selection. Using quantum information techniques including state and process tomography, we characterize strategies for producing Bell states and multi-photon entangled states
The problem of photon-pair transmission through an absorbing medium is discussed using two different approaches, a perturbative Fermi's golden rule calculation and a calculation using photon wavefunction description. The two approaches produce identical results regarding the two-photon absorption characteristics, despite their conceptual differences
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