Engineering topics

Weinfurter, Harald

Publications and source records attributed to Weinfurter, Harald.

3 records

DOE OSTI2023

Quantum networks with neutral atom processing nodes

Abstract Quantum networks providing shared entanglement over a mesh of quantum nodes will revolutionize the field of quantum information science by offering novel applications in quantum computation, enhanced precision in networks of sensors and clocks, and efficient quantum communication over large distances. Recent experimental progress with individual neutral atoms demonstrates a high potential for implementing the crucial components of such networks. We highlight latest developments and near-term prospects on how arrays of individually controlled neutral atoms are suited for both efficient remote entanglement generation and large-scale quantum information processing, thereby providing the necessary features for sharing high-fidelity and error-corrected multi-qubit entangled states between the nodes. We describe both the functionality requirements and several examples for advanced, large-scale quantum networks composed of neutral atom processing nodes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2014

Tapered fiber coupling of single photons emitted by a deterministically positioned single nitrogen vacancy center

A diamond nano-crystal hosting a single nitrogen vacancy (NV) center is optically selected with a confocal scanning microscope and positioned deterministically onto the subwavelength-diameter waist of a tapered optical fiber (TOF) with the help of an atomic force microscope. Based on this nano-manipulation technique, we experimentally demonstrate the evanescent coupling of single fluorescence photons emitted by a single NV-center to the guided mode of the TOF. By comparing photon count rates of the fiber-guided and the free-space modes and with the help of numerical finite-difference time domain simulations, we determine a lower and upper bound for the coupling efficiency of (9.5 ± 0.6)% and (10.4 ± 0.7)%, respectively. Our results are a promising starting point for future integration of single photon sources into photonic quantum networks and applications in quantum information science.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2011

Coherence of a qubit stored in Zeeman levels of a single optically trapped atom

We experimentally investigate the coherence properties of a qubit stored in the Zeeman substates of the 5{sup 2}S{sub 1/2}, F=1 hyperfine ground level of a single optically trapped {sup 87}Rb atom. Larmor precession of a single atomic spin-1 system is observed by preparing the atom in a defined initial spin state and then measuring the resulting state after a programmable period of free evolution. Additionally, by performing quantum-state tomography, maximum knowledge about the spin coherence is gathered. By using an active magnetic field stabilization and without application of a magnetic guiding field, we achieve transverse and longitudinal dephasing times of T{sub 2}{sup *}=75-150 {mu}s and T{sub 1}>0.5 ms, respectively. We derive the light-shift distribution of a single atom in the approximately harmonic potential of a dipole trap and show that the measured atomic spin coherence is limited mainly by residual position- and state-dependent effects in the optical trapping potential. The improved understanding enables longer coherence times, an important prerequisite for future applications in long-distance quantum communication and computation with atoms in optical lattices, or for a loophole-free test of Bell's inequality.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗