Wide-field time-of-flight measurements of highly scattering media.

We present a setup that makes use of a time-resolved single-photon camera to determine the scattering parameters of media. The measurement is realized in a non-contact way, both for the illumination laser and the detection. By fitting the time-of-flight acquired distributions at different spatial positions with the diffusion equation, we retrieve the reduced scattering coefficients of a highly diffusive isotropic reference media for wavelengths in the range from 540 to 840 nm.

Experimental requirements for entangled two-photon spectroscopy.

Coherently controlling the spectral properties of energy-entangled photons is a key component of future entangled two-photon spectroscopy schemes that are expected to provide advantages with respect to classical methods. We present here an experimental setup based on a grating compressor. It allows for the spectral shaping of entangled photons with a sevenfold increase in resolution, compared to previous setups with a prism compressor. We evaluate the performances of the shaper by detecting sum frequency generation in a nonlinear crystal with both classical pulses and entangled photon pairs. The efficiency of both processes is experimentally compared and is in accordance with a simple model relating the classical and entangled two-photon absorption coefficients. Finally, the entangled two-photon shaping capability is demonstrated by implementing an interferometric transfer function.

Characterization of space-momentum entangled photons with a time resolving CMOS SPAD array.

Single-photon avalanche diode arrays can provide both the spatial and temporal information of each detected photon. We present here the characterization of spatially entangled photons with a 32 × 32 pixel sensor, specifically designed for quantum imaging applications. The sensor is time-tagging each detection event at pixel level with sub-nanosecond accuracy within frames of 50 ns. The spatial correlations between any number of detections in a defined temporal window can thus be directly extracted from the data.The space-momentum entanglement of photon pairs is demonstrated by violating an EPR-type inequality directly from the measured near-field correlations and far-field anti-correlations.

Coincidence detection of spatially correlated photon pairs with a monolithic time-resolving detector array.

We demonstrate coincidence measurements of spatially entangled photons by means of a multi-pixel based detection array. The sensor, originally developed for positron emission tomography applications, is a fully digital 8×16 silicon photomultiplier array allowing not only photon counting but also per-pixel time stamping of the arrived photons with an effective resolution of 265 ps. Together with a frame rate of 500 kfps, this property exceeds the capabilities of conventional charge-coupled device cameras which have become of growing interest for the detection of transversely correlated photon pairs. The sensor is used to measure a second-order correlation function for various non-collinear configurations of entangled photons generated by spontaneous parametric down-conversion. The experimental results are compared to theory.

Ultrashort pulses characterization by quantum state tomography.

We apply the method of quantum state tomography for the reconstruction of classical laser pulses. The scheme is based on linear inversion, has no need for iterative inversion algorithm or deconvolution, and accounts for partial coherence. The reconstruction protocol is successfully tested on amplitude and phase shaped femtosecond pulses.

Adaptive quantum state estimation of an entangled qubit state.

The uncertainty on the estimation of unknown parameters of a quantum state can be reduced by using adaptive measurements. Here we perform adaptive quantum-state estimation of the phase in an entangled two-qubits state. We experimentally demonstrate that the adaptive method outperforms nonadaptive methods.

Improvement of the frequency stability below the Dick limit with a continuous atomic fountain clock.

The frequency instability of a shot-noise limited atomic fountain clock is inversely proportional to its signal-tonoise ratio. Therefore, increasing the atomic flux is a direct way to improve the stability. Nevertheless, in pulsed operation, the local oscillator noise limits the performance via the Dick effect. We experimentally demonstrate here that a continuous atomic fountain allows one to overcome this limitation. In this work, we take advantage of two-laser optical pumping on a cold cesium beam to increase the useful fountain flux and, thus, to reduce the frequency instability below the Dick limit. A stability of 6 × 10(-14)τ(-1/2) has been measured with the continuous cesium fountain FOCS-2.

Gas phase sorting of fullerenes, polypeptides and carbon nanotubes.

We discuss the Stark deflectometry of micro-modulated molecular beams for the enrichment of biomolecular isomers as well as single-wall carbon nanotubes, and we demonstrate the working principle of this idea with fullerenes. The sorting is based on the species-dependent susceptibility-to-mass ratio χ/m. The device is compatible with a high molecular throughput, and the spatial micro-modulation of the beam permits one to obtain a fine spatial resolution and a high sorting sensitivity.

Thermal and electrical properties of porphyrin derivatives and their relevance for molecule interferometry.

The authors present new measurements of thermal and electrical properties for two porphyrin derivatives. They determine their sublimation enthalpy from the temperature dependence of the effusive beam intensity. The authors study H2TPP and Fe(TPP)Cl in matter-wave interferometry. Both molecules have nearly equal de Broglie wavelengths but different internal characteristics: only Fe(TPP)Cl exhibits an electric dipole moment of about 2.7 D and the authors discuss its influence on the molecular interference pattern. The authors add an external electric force field to the interferometer and use it to measure the scalar polarizability. They compare their experimental values alpha(H2TPP)=105+/-4+/-6 A3 and alpha(Fe(TPP)Cl)=102+/-9+/-6 A3 to ab initio calculations and they discuss the influence of thermal excitations on the polarizability.

Sublimation enthalpy of dye molecules measured using fluorescence.

We present an in-flight fluorescence detection scheme for molecular beams which is applied to determine the enthalpy of sublimation of dye molecules. We investigate tetraphenylporphyrin (TPP), porphine, and nile red, which are believed to be suitable candidates for molecular de Broglie wave interferometry. The measured values are H(sub)(TPP)=142+/-3 kJ/mol, H(sub)(porphine)=87+/-3 kJ/mol, and H(sub)(nile red)=66+/-2 kJ/mol. For TPP, sublimation enthalpies differ in the literature by more than a factor of 2. Our measurements confirm a value at the lower end of this scale. We discuss changes in the character of the molecular flow with the source temperature as a prime reason for discrepancies in the published data.

Quantum correlations with spacelike separated beam splitters in motion: experimental test of multisimultaneity.

Multisimultaneity is a causal model of relativistic quantum physics which assigns a real time ordering to any set of events, much in the spirit of the pilot-wave picture. Contrary to standard quantum mechanics, it predicts a disappearance of the correlations in a Bell-type experiment when both analyzers are in relative motion such that each one, in its own inertial reference frame, is first to select the output of the photons. We tested this prediction using acousto-optic modulators as moving beam splitters and interferometers separated by 55 m. We did not observe any disappearance of the correlations, in agreement with quantum mechanics.