The generation of a register of highly coherent, but independent, qubits is a prerequisite to performing universal quantum computation. Here we introduce a qubit encoded in two nuclear spin states of a single 87Sr atom and demonstrate coherence approaching the minute-scale within an assembled register of individually-controlled qubits. While other systems have shown impressive coherence times through some combination of shielding, careful trapping, global operations, and dynamical decoupling, we achieve comparable coherence times while individually driving multiple qubits in parallel. We highlight that even with simultaneous manipulation of multiple qubits within the register, we observe coherence in excess of 105 times the current length of the operations, with [Formula: see text] seconds. We anticipate that nuclear spin qubits will combine readily with the technical advances that have led to larger arrays of individually trapped neutral atoms and high-fidelity entangling operations, thus accelerating the realization of intermediate-scale quantum information processors.

Submitted for the DAMOP19 Meeting of The American Physical Society A New Apparatus for Deterministic Atom Arrays in Photonic Crystal Waveguides ALEXANDER BURGERS, XINGSHENG LUAN, JEANBAPTISTE BEGUIN, ZHONGZHONG QIN, LUCAS PENG, H JEFF KIMBLE, Caltech — Integrating ultracold atoms with nanophotonics enables the exploration of new paradigms in quantum optics and many body physics. Advanced fabrication capabilities for low-loss dielectrics materials provide powerful tools to engineer band structure and light-matter coupling of photons and atoms. For example, dispersionengineered photonic crystal waveguides (PCWs) permit not only stable trapping and probing of ultracold neutral atoms via interactions with guided mode (GM) light, but also the possibility to study the physics of strong, photon-mediated interactions between atoms, as well as atom mediated photon-photon interactions. Our current Caltech system to explore such phenomena consists of a quasi-one-dimensional PCW whose band structure arises from periodic modulation of the dielectric structure. Our upgraded system utilizes a silicate bonding technique to adhere the chip containing the PCWs to a glass cell for large optical access and ultra-high vacuum operation. With the improved optical access and small glass cell we are able to deterministically couple single atoms to the PCWs using an optical tweezer. The extension of the single tweezer to arrays of atoms in optical tweezers allows us to investigate the string atom-light interactions mediated by the PCW. Alexander Burgers Caltech Date submitted: 31 Jan 2019 Electronic form version 1.4

Integrating cold atoms with nanophotonics enables the exploration of new paradigms in quantum optics and many body physics. Advanced fabrication capabilities for low-loss dielectric materials provide powerful tools to engineer band structure and light-matter couplings between photons and atoms. The current system at Caltech to explore such phenomena consists of a quasi-one-dimensional photonic crystal waveguide whose band structure arises from periodic modulation of the dielectric structure [1, 2]. The waveguide design gives rise to stable trap sites for atoms at each unit cell of the crystal (150 sites for the 1D waveguide). Atoms localized in these traps will interact with one another via guided modes of the waveguide creating a versatile system that can be utilized for both quantum memories and quantum simulation[3–5]. A detailed understanding of the atomic delivery near the device is required before any trap sites within the waveguide can be loaded [6]. To deliver atoms to the structure they are first confined into a 1D lattice using two counter-propagating, free-space dipole beams. By chirping the frequency of a single lattice beam the atoms are transported to the structure 2 cm from the lattice loading site. A guided mode probe, resonant with the atoms, in the photonic crystal structure signals the atom arrival to the device. The intensity maxima of the 1D lattice (where the atoms are trapped) pass through the device at a temporal spacing given by the inverse of the chirp frequency. So, by temporally registering the probe data between the lattice intensity maxima we build a histogram of the atom arrival in one lattice period. These time vs. detuning spectra convey important information about atomic trajectories near the device and inform the ultimate goal of trapping along the photonic crystal waveguide. To better understand the atomic delivery we conducted detailed simulations of atomic trajectories near the structure including calculations of the atomic spectra in the presence of guided mode fields. These guided mode fields will ultimately be used to create the desired trapping potentials, so a detailed understanding of the atomic interaction with such fields and drawing direct correspondence between simulation and experiment is essential. Fig. 1 shows the comparison between simulation and experiment for a single guided mode field used to Stark shift atoms interacting with different regions of the device. The direct correspondence between simulation and experiment is apparent in these data; moreover, the data indicate a clear separation of the atomic sample into different classes of atoms experiencing the Stark shifting beam at different arrival times to the structure. I