A Platform of Rydberg-Dressed Cesium Atoms for Quantum Control Applications.

Yuan‐Yu Jau, Aaron M. Hankin, Tyler Keating +2 more

Ognjen Marković, Victoria Borish, Jacob Hines +1 more

Aaron M. Hankin, Yuan‐Yu Jau, Grant W. Biedermann

Grant W. Biedermann

We demonstrate a Rydberg-dressed ground-state blockade that provides a strong tunable interaction energy (~1 MHz in units of Planck's constant) between spins of individually trapped cesium atoms.With this interaction we directly produce Bell-state entanglement between two atoms with a fidelity ≥ 81(2)%, excluding atom loss events, and ≥ 60(3)% when loss is included [arXiv].Our method is based on a new technique that produces a blockade of Rydberg-dressed ground states.This approach allows single-step, direct entanglement of long-lived ground (clock) states in our cesium atoms.The on-demand interaction we employ-Rydberg-dressed ground states-is a long sought after fundamental capability for numerous proposals spanning from new phases of matter in ultracold quantum gases to spin-squeezed metrology in clocks and quantum computation protocols.We not only clearly measure this elusive Rydberg-dressed interaction, but also employ it to demonstrate high fidelity Bell-state generation.The entanglement generation differs from previous work in a fundamental way; the probability remains entirely in the Rydberg-dressed ground state, freeing the approach from the experimental burden of coherently exciting optical transitions to and from the Rydberg states.In principle Rydberg-dressed atoms are more insensitive to various decoherence mechanisms and lead to a better quantum control fidelity [Keating PRA].In addition, the interaction we demonstrate is nearly 4 orders of magnitude larger than that produced in the typical experiment based on ultra cold collisions.

Michael J. Martin

Aaron M. Hankin

With the advent of laser cooling and trapping, neutral atoms have become a foundational source of accuracy for applications in metrology and are showing great potential for their use as qubits in quantum information. In metrology, neutral atoms provide the most accurate references for the measurement of time and acceleration. The unsurpassed stability provided by these systems make neutral atoms an attractive avenue to explore applications in quantum information and computing. However, to fully investigate the field of quantum information, we require a method to generate entangling interactions between neutral-atom qubits. Recent progress in the use of highly-excited Rydberg states for strong dipolar interactions has shown great promise for controlled entanglement using the Rydberg blockade phenomenon. I report the use of singly-trapped cesium atoms as qubits for applications in metrology and quantum information. Each atom provides a physical basis for a single qubit by encoding the required information into the ground-state hyperfine structure of cesium. Through the manipulation of these qubits with microwave and optical frequency sources, we demonstrate the capacity for arbitrary single-qubit control by driving qubit rotations in three orthogonal directions on the Bloch sphere. With this control, we develop an atom interferometer that far surpasses the force sensitivity of other approaches by applying the well-established technique of light-pulsed atom-matterwave interferometry to single atoms. Following this, we focus on two-qubit interactions using highly-excited Rydberg states. Through the development of a unique single-photon approach to Rydberg excitation using an ultraviolet laser at 319 nm, we observe the Rydberg blockade interaction between atoms separated by 6.6(3) microns. Motivated by the observation of Rydberg blockade, we study the application of Rydberg-dressed states for a quantum controlled-phase gate. Using a realistic simulation of the dressed-state dynamics, we calculate a controlled-phase gate fidelity of 94% that is primarily limited by Doppler frequency shifts. Finally, we employ our single-photon excitation laser to measure the Rydberg-dressed interaction, thus demonstrating the viability of this approach.