Single Cs Atoms Research Articles

Formation of Ultracold Molecules by Merging Optical Tweezers.

We demonstrate the formation of a single RbCs molecule during the merging of two optical tweezers, one containing a single Rb atom and the other a single Cs atom. Both atoms are initially predominantly in the motional ground states of their respective tweezers. We confirm molecule formation and establish the state of the molecule formed by measuring its binding energy. We find that the probability of molecule formation can be controlled by tuning the confinement of the traps during the merging process, in good agreement with coupled-channel calculations. We show that the conversion efficiency from atoms to molecules using this technique is comparable to magnetoassociation.

Power of a Quasispin Quantum Otto Engine at Negative Effective Spin Temperature

A negative-temperature quantum heat engine is experimentally implemented with a single Cs atom in an Rb bath, demonstrating how negative temperatures can both enhance the output power and reduce fluctuations in comparison to positive temperatures.

Preparation of 87Rb and 133Cs in the motional ground state of a single optical tweezer

We report simultaneous Raman sideband cooling of a single 87Rb atom and a single 133Cs atom held in separate optical tweezers at 814 nm and 938 nm, respectively. Starting from outside the Lamb-Dicke regime, after 45 ms of cooling we measure probabilities to occupy the three-dimensional motional ground state of for Rb and for Cs. Our setup overlaps the Raman laser beams used to cool Rb and Cs, reducing hardware requirements by sharing equipment along the same beam path. The cooling protocol is scalable, and we demonstrate cooling of single Rb atoms in an array of four tweezers. After motional ground-state cooling, a 938 nm tweezer is translated to overlap with a 814 nm tweezer so that a single Rb and a single Cs atom can be transferred into a common 1064 nm trap. By minimising the heating during the merging and transfer, we prepare the atoms in the relative motional ground state with an efficiency of . This is a crucial step towards the formation of single RbCs molecules confined in optical tweezer arrays.

Tailored optical potentials for Cs atoms above waveguides with focusing dielectric nano-antenna.

Tuning the near field using all-dielectric nano-antennas offers a promising approach for trapping atoms, which could enable strong single-atom-photon coupling. Here we report the numerical study of an optical trapping of a single Cs atom above a waveguide with a silicon nano-antenna, which produces a trapping potential for atoms in a chip-scale configuration. Using counter-propagating incident fields, bichromatically detuned from the atomic cesium D-lines, we numerically investigate the dependence of the optical potential on the nano-antenna geometry. We tailor the near-field potential landscape by tuning the evanescent field of the waveguide using a toroidal nano-antenna, a configuration that enables trapping of ultracold Cs atoms. Our research opens up a plethora of trapping atoms applications in a chip-scale manner, from quantum computing to quantum sensing, among others.

Rydberg-blockade controlled-not gate and entanglement in a two-dimensional array of neutral-atom qubits

We present experimental results on two-qubit Rydberg blockade quantum gates and entanglement in a two-dimensional qubit array. Without post selection against atom loss we achieve a Bell state fidelity of $0.73\pm 0.05$, the highest value reported to date. The experiments are performed in an array of single Cs atom qubits with a site to site spacing of $3.8 ~ \mu\rm m$. Using the standard protocol for a Rydberg blockade C$_Z$ gate together with single qubit operations we create Bell states and measure their fidelity using parity oscillations. We analyze the role of AC Stark shifts that occur when using two-photon Rydberg excitation and show how to tune experimental conditions for optimal gate fidelity.

Dissociation of molecular oxygen on unpromoted and cesium‐promoted Ag(111) surfaces

Density functional calculations for the dissociation of molecular oxygen on a Ag10 cluster model (seven surface and three subsurface atoms) of the [111] surface of silver are presented. The calculations show that the reaction pathway for the dissociation of molecular oxygen depends on the amount of cesium present on the surface. For the unpromoted surface, dissociation should have a low rate as the process is activated. As a single Cs atom is added to the cluster, O2 should readily dissociate since the process is kinetically and thermochemically favored. However, as a second Cs atom is added, the dissociation of O2 is quenched as the process is highly activated.