arXiv subjects

Matthias Steiner

Publications and source records attributed to Matthias Steiner.

9 recordsLinked to original sources

arXiv2018

Transmission spectroscopy of a single atom in the presence of tensor light shifts

We investigate the interplay between Zeeman and light shifts in the transmission spectrum of an optically trapped, spin-polarized Rubidium atom. The spectral shape of the transmission changes from multiple, broad resonances to a single, narrow Lorentzian with a high resonant extinction value when we increase the magnetic field strength and lower the depth of the dipole trap. We present an experimental configuration well-suited for quantum information applications in that it enables not only efficient light-atom coupling but also a long coherence time between ground state hyperfine levels.

physics.atom-ph↗

arXiv2017

Polarization gradient cooling of single atoms in optical dipole traps

We experimentally investigate $σ^+$-$σ^-$ polarization gradient cooling~(PGC) of a single $^{87}$Rb atom in a tightly focused dipole trap and show that the cooling limit strongly depends on the polarization of the trapping field. For optimized cooling light power, the temperature of the atom reaches~$10.4(6)\,μ$K in a linearly polarized trap, approximately five times lower than in a circularly polarized trap. The inhibition of PGC is qualitatively explained by the fictitious magnetic fields induced by the trapping field. We further demonstrate that switching the trap polarization from linear to circular after PGC induces only minor heating.

physics.atom-ph↗

arXiv2017

Single atoms coupled to a near-concentric cavity

Concentric cavities can lead to strong photon-atom coupling without a need for high finesse or small physical-cavity volume. In a proof-of-principle experiment of this concept we demonstrate coupling of single Rb atoms to a 11mm long near-concentric cavity with a finesse F=138(2). Operating the cavity 1.65(1)$μ$m shorter than the critical length, we observe an atom-cavity coupling constant $g_0=2π\times 5.0(2)\,$MHz which exceeds the natural dipole decay rate $γ$ by a factor $g_0/γ=1.7(1)$.

quant-ph↗

arXiv2017

Nonlinear photon-atom coupling with 4Pi microscopy

Implementing nonlinear interactions between single photons and single atoms is at the forefront of optical physics. Motivated by the prospects of deterministic all-optical quantum logic, many efforts are currently underway to find suitable experimental techniques. Focusing the incident photons onto the atom with a lens yielded promising results, but is limited by diffraction to moderate interaction strengths. However, techniques to exceed the diffraction limit are known from high-resolution imaging. In this work, we adapt a super-resolution imaging technique, 4Pi microscopy, to efficiently couple light to a single atom. We observe 36.6(3)% extinction of the incident field, and a modified photon statistics of the transmitted field -- indicating nonlinear interaction at the single-photon level.

quant-ph↗

arXiv2017

Photon bandwidth dependence of light-matter interaction

We investigate the scattering of single photons by single atoms and, in particular, the dependence of the atomic dynamics and the scattering probability on the photon bandwidth. We tightly focus the incident photons onto a single trapped~$^{87}${Rb} atom and use the time-resolved transmission to characterize the interaction strength. Decreasing the bandwidth of the single photons from 6 to~2 times the atomic linewidth, we observe an increase in atomic peak excitation and photon scattering probability.

quant-ph↗

arXiv2016

Quantifying the role of thermal motion in free-space light-atom interaction

We demonstrate 17.7(1)% extinction of a weak coherent field by a single atom. We observe a shift of the resonance frequency and a decrease in interaction strength with the external field when the atom, initially at 21(1) $μ$K, is heated by the recoil of the scattered photons. Comparing to a simple model, we conclude that the initial temperature reduces the interaction strength by less than 10%.

quant-ph↗

arXiv2016

Time-resolved Scattering of a Single Photon by a Single Atom

Scattering of light by matter has been studied extensively in the past. Yet, the most fundamental process, the scattering of a single photon by a single atom, is largely unexplored [1-3]. One prominent prediction of quantum optics is the deterministic absorption of a traveling photon by a single atom, provided the photon waveform matches spatially and temporally the time-reversed version of a spontaneously emitted photon [4-12]. Here, we experimentally address this prediction and investigate the influence of the temporal profile of the photon on the scattering dynamics using a single trapped atom and heralded single photons. In a time-resolved measurement of the atomic excitation we find a 56(11)% increase of the peak excitation by photons with an exponentially rising profile compared to a decaying one. This result demonstrates that tailoring the envelope of single photons enables precise control of the photon-atom interaction.

quant-ph↗

arXiv2012

A single ion coupled to an optical fiber cavity

We present the realization of a combined trapped-ion and optical cavity system, in which a single Yb^+ ion is confined by a micron-scale ion trap inside a 230 mum-long optical fiber cavity. We characterize the spatial ion-cavity coupling and measure the ion-cavity coupling strength using a cavity-stimulated Lambda-transition. Owing to the small mode volume of the fiber resonator, the coherent coupling strength between the ion and a single photon exceeds the natural decay rate of the dipole moment. This system can be integrated into ion-photon quantum networks and is a step towards cavity quantum-electrodynamics (cavity-QED) based quantum information processing with trapped ions.

quant-ph↗

arXiv2011

Laser spectroscopy and cooling of Yb+ ions on a deep-UV transition

We perform laser spectroscopy of Yb+ ions on the 4f14 6s 2S_{1/2} - 4f13 5d 6s 3D[3/2]_{1/2} transition at 297 nm. The frequency measurements for 170Yb+, 172Yb+, 174Yb+, and 176Yb+ reveal the specific mass shift as well as the field shifts. In addition, we demonstrate laser cooling of Yb+ ions using this transition and show that light at 297 nm can be used as the second step in the photoionization of neutral Yb atoms.

physics.atom-ph↗