arXiv subjects

N. Röck

Publications and source records attributed to N. Röck.

3 recordsLinked to original sources

arXiv2013

Atom-atom entanglement by single-photon detection

A scheme for entangling distant atoms is realized, as proposed in the seminal paper by Cabrillo et al. [Phys. Rev. A 59, 1025 (1999)]. The protocol is based on quantum interference and detection of a single photon scattered from two effectively one meter distant laser-cooled and trapped atomic ions. The detection of a single photon heralds entanglement of two internal states of the trapped ions with high rate and with a fidelity limited mostly by atomic motion. Control of the entangled state phase is demonstrated by changing the path length of the single-photon interferometer.

quant-ph↗

arXiv2012

Faraday rotation of a tightly focussed beam from a single trapped atom

Faraday rotation of a laser field induced by a single atom is demonstrated by tightly focussing a linearly polarized laser beam onto a laser-cooled ion held in a harmonic Paul trap. The polarization rotation signal is further used to measure the phase-shift associated with electromagnetically-induced-transparency and to demonstrate read-out of the internal state on the qubit transition with a detection fidelity of 98 $\pm$ 1%. These results have direct implications for single atom magnetometery and dispersive read-out of atomic superpositions.

physics.atom-ph↗

arXiv2012

Interferometric thermometry of a single sub-Doppler cooled atom

Efficient self-interference of single-photons emitted by a sideband-cooled Barium ion is demonstrated. First, the technical tools for performing efficient coupling to the quadrupolar transition of a single $^{138}$Ba$^{+}$ ion are presented. We show efficient Rabi oscillations of the internal state of the ion using a highly stabilized 1.76 $μm$ fiber laser resonant with the S$_{1/2}$-D$_{5/2}$ transition. We then show sideband cooling of the ion's motional modes and use it as a means to enhance the interference contrast of the ion with its mirror-image to up to 90%. Last, we measure the dependence of the self-interference contrast on the mean phonon number, thereby demonstrating the potential of the set-up for single-atom thermometry close to the motional ground state.

physics.atom-ph↗