arXiv subjects

B. Weber

Publications and source records attributed to B. Weber.

4 recordsLinked to original sources

arXiv2009

Shaping the Phase of a Single Photon

While the phase of a coherent light field can be precisely known, the phase of the individual photons that create this field, considered individually, cannot. Phase changes within single-photon wave packets, however, have observable effects. In fact, actively controlling the phase of individual photons has been identified as a powerful resource for quantum communication protocols. Here we demonstrate the arbitrary phase control of a single photon. The phase modulation is applied without affecting the photon's amplitude profile and is verified via a two-photon quantum interference measurement, which can result in the fermionic spatial behaviour of photon pairs. Combined with previously demonstrated control of a single photon's amplitude, frequency, and polarisation, the fully deterministic phase shaping presented here allows for the complete control of single-photon wave packets.

quant-ph↗

arXiv2008

Fast Excitation and Photon Emission of a Single-Atom-Cavity System

We report on the fast excitation of a single atom coupled to an optical cavity using laser pulses that are much shorter than all other relevant processes. The cavity frequency constitutes a control parameter that allows the creation of single photons in a superposition of two tunable frequencies. Each photon emitted from the cavity thus exhibits a pronounced amplitude modulation determined by the oscillatory energy exchange between the atom and the cavity. Our technique constitutes a versatile tool for future quantum networking experiments.

quant-ph↗

arXiv2008

Photon-Photon Entanglement with a Single Trapped Atom

An experiment is performed where a single rubidium atom trapped within a high-finesse optical cavity emits two independently triggered entangled photons. The entanglement is mediated by the atom and is characterized both by a Bell inequality violation of S=2.5, as well as full quantum-state tomography, resulting in a fidelity exceeding F=90%. The combination of cavity-QED and trapped atom techniques makes our protocol inherently deterministic - an essential step for the generation of scalable entanglement between the nodes of a distributed quantum network.

quant-ph↗

arXiv2006

Quantitative modeling of laser speckle imaging

We have analyzed the image formation and dynamic properties in laser speckle imaging (LSI) both experimentally and with Monte-Carlo simulation. We show for the case of a liquid inclusion that the spatial resolution and the signal itself are both significantly affected by scattering from the turbid environment. Multiple scattering leads to blurring of the dynamic inhomogeneity as detected by LSI. The presence of a non-fluctuating component of scattered light results in the significant increase in the measured image contrast and complicates the estimation of the relaxation time. We present a refined processing scheme that allows a correct estimation of the relaxation time from LSI data.

cond-mat.soft↗