We present a fully operational ultra-stable-laser system for cooling, trapping and manipulating Rydberg states in optical tweezer arrays of neutral Sr-atoms. Some CW-lasers are phase-coherently disciplined by an ultra-low-noise comb referenced to a sub-Hz ultra-stable-laser.
Quantum technologies are nowadays emerging as enabling tools for practical applications, such as quantum sensing, quantum computing and quantum metrology. Lasers play a central role in many of these technological platforms, e.g. for atomic clocks, ion-based or neutral atom-based quantum computers or atom interferometers. Here we present a complete laser system to cool, trap and control strontium atoms in an optical lattice or in tweezer arrays. A sub-Hz linewidth master laser, locked to a high-finesse optical cavity provides the frequency reference for an ultra-low noise comb. The rack-mounted laser system consists of all cooling, repumping, and clock lasers stabilized to the optical frequency comb. Each of the involved laser frequencies can therefore be tuned and mapped in the frequency domain with a high degree of stability. The system is controlled via a software interface, allowing to operate the cold-atom-based physics package autonomously. The system is tailored for the operation of 88Sr or 87Sr optical lattice clocks, or for quantum computing applications, but other sub-Hz lasers could be obtained by phase locking additional clock laser frequencies to the ultra-stable comb, enabling convenient and accurate optical frequency ratio measurements. The laser system architecture and the relevant characterization measurements will be presented, proposing some user-cases such as quantum computing and atom interferometry on strontium atoms. This represents a technological leap for quantum optics, allowing to explore further applications of quantum sensors outside a traditional lab.
Subwavelength atomic tweezer arrays, in which atoms can be positioned at distances smaller than their emission wavelength, have been proposed as a versatile platform to study collective emission phenomena, such as superradiance and subradiance. Experimentally, the realization of such arrays has been a challenge as typical emission wavelengths in the visible or near-infrared are short compared to typical tweezer spacings in the micrometer range. Here, we use 88Sr atoms in optical tweezer arrays to access a mid-infrared transition at 2,923 nm (5s5p3P2→5s4d3D3). We identify a magic trapping wavelength at 597.14(3) nm and demonstrate single-atom preparation and imaging with high fidelity. In addition, using 2,923 nm light, we demonstrate resolved-sideband cooling of tweezer-trapped strontium. Beyond enabling studies of collective emission phenomena in flexible arrangements of atoms, our platform opens novel opportunities for dipolar many-body physics and enhanced control over Rydberg dynamics and the strontium fine-structure qubit.
Quantum technologies, spanning from sensing and metrology to simulations and computing, rely upon precise and low noise laser systems. Currently, we are witnessing a paradigm shift, where laboratory-based experiments are engineered such to develop reliable operating devices. The goal of providing continuous operation is key to enable their deployment for, e.g., PNT applications or cloud-based quantum computing services. Ultra-low noise laser systems are becoming integral part of these quantum devices due to their pivotal role in the effective functioning of the physics package. In fact, the performance are fundamentally linked to the noise properties of the driving laser fields, imposing the need of a careful choice of the appropriate sources, their spectral properties, and their stabilization. Here we present some of our recent ultra-stable laser system engineered for enabling several applications, we will describe ultra-stable comb and laser systems for quantum computing using neutral Yb, Sr, Rb, or Cs atoms, electric field sensing with Rydberg Rb atoms, and portable compact comb systems to enable uninterrupted operation of optical clocks in the field. A detailed noise analysis of the systems will be presented.
Neutral atoms are a ubiquitous platform for various quantum sciences with applications in quantum computing, simulation, and metrology across many different atomic species. In these systems, control over the electronic states is given by suitable laser pulses typically applied at the single-particle level. Here, we present fast coherent control over the meta-stable clock states in bosonic strontium-88 using two- and three-photon couplings. Compared to the direct single-photon drive on these transitions, the realistically achievable Rabi frequencies are substantially higher at significantly relaxed magnetic field strength. By applying a magnetic quantization axis under a judiciously chosen angle with respect to the linear trap polarization, we realize an optical qutrit comprising the ground state 1S0 as well as both clock states 3P0 and 3P2, and characterize in detail the coherence of the system. Remarkably, the observed coherence time on the fine-structure qubit (given by the 3P0 and 3P2,mj=0 states) of 715(30) ms demonstrates, for the first time, that state-of-the-art coherence times are compatible with tweezer-based polarizability-engineered trapping potentials, which is applicable across a broad range of wavelengths and atomic species. We identify laser phase noise as the main limitation of the current operation fidelity and discuss methods for characterizing, modelling, and compensating optical phase noise. The multi-photon couplings not only allow for substantially faster Rabi frequencies under realistic experimental conditions, but additionally offer controlled dissipation via the 3P1 state, which we use to demonstrate a measurement-free qubit reset. Combined with three-photon couplings to the 3P2 clock state, we realize resolved sideband cooling in an optical lattice potential and benchmark the fine-structure qubit at various infrared wavelengths. In addition, we introduce a hybrid lattice-tweezer setup and demonstrate the preparation of programmable atom configurations in a single plane of the two-dimensional optical lattice potential. Using single-site addressing with optical tweezers, we present a protocol for the iterative assembly of large-scale atom arrays. Furthermore, we use the lattice-tweezer combination to continuously operate a configurable atom array, which provides means to overcome scaling limitations by repeatedly adding atoms to the system and enables entirely novel approaches to operating neutral-atom arrays. To enable reliable image processing with a fast reconstruction of the lattice occupation, we introduce a novel algorithm based on a convolutional neural network, which provides a rapid and noise-resilient reconstruction compatible with arbitrary lattice geometries. Moreover, we benchmark a new phase-only spatial light modulator based on a micromirror array, which paves the way towards holographic beam shaping at fast update rates compatible with a broad range of wavelengths, including the ultraviolet spectral range.
Neutral atoms for quantum computing applications show promise in terms of scalability and connectivity. We demonstrate the realization of a versatile apparatus capable of stochastically loading a 5x5 array of optical tweezers with single 88Sr atoms featuring flexible magnetic field control and excellent optical access. A custom-designed oven, spin-flip Zeeman slower, and deflection stage produce a controlled flux of Sr directed to the science chamber. In the science chamber, featuring a vacuum pressure of 3×10−11 mbar, the Sr is cooled using two laser cooling stages, resulting in ∼3×105 atoms at a temperature of 5(1) μK. The optical tweezers feature a 1/e2 waist of 0.81(2) μm, and loaded atoms can be imaged with a fidelity of ∼0.997 and a survival probability of 0.99−0.02+0.01. The atomic array presented here forms the core of a full-stack quantum computing processor targeted for quantum chemistry computational problems.