Please join us for the final AMO/QI seminar of the semester featuring Dr. Michael Mills of Quantinuum. He will be giving a talk titled: Benchmarking a racetrack trapped-ion quantum processor

Abstract:
The System Model H2, a quantum charge-coupled device (QCCD) trapped-ion system with a new racetrack-shaped trap, is Quantinuum's latest generation of quantum computers. The new system successfully incorporates several technologies crucial to future scalability, including electrode broadcasting, multi-layer RF routing, and magneto-optical trap (MOT) loading, while maintaining, and in some cases exceeding, the gate fidelities of previous QCCD systems.

We describe the operations in the H2 system and benchmark the performance of primitive operations, including single-qubit and two-qubit gate fidelity, state preparation and measurement fidelity, and crosstalk errors. Further, we highlight several applications using the H2 system, such as the creation of non-abelian topological order and anyons. Finally, we discuss upgrades to the H2 system.

Please join us for this week’s AMO/QI seminar to celebrate Dr. Neil Glikin’s completion of his dissertation! After his talk there will be a celebratory lunch. Here is a zoom link in case you cannot attend in person.
He will be giving a talk titled: Creating and Destroying Rotational Coherence with Trapped Ions

Abstract:
Far from being just qubits, trapped ions are also near-ideal quantum harmonic oscillators thanks to their external motion. Over the past few decades, researchers have engineered oscillator motion into a wide variety of interesting, exotic, and useful nonclassical states. This talk is centered around a system which fundamentally deviates from this usual situation: By allowing ions to physically rotate around one another, their motion becomes rotor-like rather than oscillator-like. The key to realizing this system is a surface-electrode ion trap which is highly circularly symmetric. Our trapped-ion rotor carries the promise of unlocking a new rotor-based category of experiments. I will discuss how we prepare the quantum state of the rotor, in particular how we create coherent superpositions of angular momenta. I will also discuss how we have used this system to systematically probe the open quantum dynamics of a rotor interacting with its environment. Here, we have observed for the first time simple scaling laws for rotor decoherence. Finally, I will discuss a proposal for an experiment in which one can directly observe the consequences of exchanging a pair of identical particles. This will be done by superposing a reference state with one in which the particles have rotated by pi radians relative to each other.

Please join us for this week’s AMO/QI seminar featuring Dr. Jon Simon, Stanford. He will be giving a talk titled: Racing to the Bottom: Low Finesse, Small Waist Cavity QED

Abstract:
In this seminar I’ll tell the story of cavity quantum electrodynamics (cQED) from first principles, building towards a new type of sub-micron waist resonator recently developed in the Simon/Schuster collaboration at Stanford. We will start by developing physical intuition for cooperativity, the figure of merit that controls performance of light/matter coupled systems including photon collection efficiency, cavity-mediated information exchange fidelity, and even coherence of interactions of photonic quasi-particle. Maximizing cooperativity will push us in either of two directions; (1) high finesses or (2) small mode waists. The high-finesse route is well explored by many leaders in the field of cQED, so I will emphasize the quest to small mode waist resonators, motivating near-concentric resonators, bow-tie resonators, and finally, our lens cavities. These lens cavities sport mode waists below a micron, entering the strong coupling regime at finesses well below 100. I’ll share preliminary data demonstrating single-atom coupling to such a cavity, and a test-bench demonstration of an array of small waist cavities that we intend to integrate with an atom array.

Please join us for this week’s AMO/QI Seminar for Dr. Jermey Axelrod’s Dissertation Celebration! Congratulations!! He will give a talk titled: A Laser Phase Plate for Transmission Electron Microscopy

Abstract: 

Low image contrast is a major limitation in transmission electron microscopy, since samples with low atomic number only weakly phase-modulate the illuminating electron beam, and beam-induced sample damage limits the usable electron dose. The contrast can be increased by converting the electron beam's phase modulation into amplitude modulation using a phase plate, a device that applies a pi/2 radian phase shift to part of the electron beam after it has passed through the sample. Previous phase plate designs rely on material placed in or near the electron beam to provide this phase shift. This results in image aberrations, an inconsistent time-varying phase shift, and resolution loss when the electron beam charges, damages, or is scattered from the material.

In this seminar, I will present the theory, design, and implementation of the laser phase plate, which instead uses a focused continuous-wave laser beam to phase shift the electron beam. A near-concentric Fabry-Perot optical cavity focuses and resonantly enhances the power of the laser beam in order to achieve the high intensity required to provide the phase shift. We demonstrate that the cavity can surpass this requirement and generate a record-high continuous-wave laser intensity of 590 GW/cm^2. By integrating the cavity into a transmission electron microscope, we show that the ponderomotive potential of the laser beam applies a spatially selective phase shift to the electron beam. This enables us to make the first experimental observation of the relativistic reversal of the ponderomotive potential.

We then theoretically analyze the properties of the contrast transfer function generated by the laser phase plate. We experimentally determine that resolution loss caused by thermal magnetic field noise emanating from electrically conductive materials in the cavity can be eliminated by designing the cavity with a sufficiently large electron beam aperture. Finally, we show that the laser phase plate provides a stable pi/2 phase shift and concomitant contrast enhancement when imaging frozen hydrated biological macromolecules. We use these images to successfully determine the structure of the molecules. This demonstrates the laser phase plate as the first stable and lossless phase plate for transmission electron microscopy.