Multi-site integrated optical addressing of trapped ions.

One of the most effective ways to advance the performance of quantum computers and quantum sensors is to increase the number of qubits or quantum resources in the system. A major technical challenge that must be solved to realize this goal for trapped-ion systems is scaling the delivery of optical signals to many individual ions. In this paper we demonstrate an approach employing waveguides and multi-mode interferometer splitters to optically address multiple 171Yb+ ions in a surface trap by delivering all wavelengths required for full qubit control. Measurements of hyperfine spectra and Rabi flopping were performed on the E2 clock transition, using integrated waveguides for delivering the light needed for Doppler cooling, state preparation, coherent operations, and detection. We describe the use of splitters to address multiple ions using a single optical input per wavelength and use them to demonstrate simultaneous Rabi flopping on two different transitions occurring at distinct trap sites. This work represents an important step towards the realization of scalable integrated photonics for atomic clocks and trapped-ion quantum information systems.

The stiffness adjustable wheel mechanism based on compliant spoke deformation.

This study proposes a variable-stiffness mechanism for non-pneumatic tires such that can actively adapt to various environments. Non-pneumatic tire is a compliant wheel structure that offers superior robustness and adaptability compared to pneumatic tires. However, the tire designed for certain terrain exhibits relatively high rolling resistance and inadequate suspension. To address these problems, a stiffness-adjustable wheel (SAW) that can modify the force applied to the contact surface is introduced in this study. In addition, the shape of SAW is optimized to maintain a desirable range of stiffness under different conditions. The optimization is conducted with experimental method, because nonlinear response of material and interference between components make it difficult to predict the characteristic of the wheel at large deformation. The SAW has potential for application in various mobile platforms to provide adequate stiffness for a variety of terrains and driving conditions.

Spontaneous emission of matter waves from a tunable open quantum system.

The decay of an excited atom undergoing spontaneous photon emission into the fluctuating quantum-electrodynamic vacuum is an emblematic  example of the dynamics of an open quantum system. Recent experiments have demonstrated that the gapped photon dispersion in periodic structures, which prevents photons in certain frequency ranges from propagating, can give rise to unusual spontaneous-decay behaviour, including the formation of dissipative bound states1-3. So far, these effects have been restricted to the optical domain. Here we demonstrate similar behaviour in a system of artificial emitters, realized using ultracold atoms in an optical lattice, which decay by emitting matter-wave, rather than optical, radiation into free space. By controlling vacuum coupling and the excitation energy, we directly observe exponential and partly reversible non-Markovian dynamics and detect a tunable bound state that contains evanescent matter waves. Our system provides a flexible platform for simulating open-system quantum electrodynamics and for studying dissipative many-body physics with ultracold atoms4-6.