A frequency comb stabilized Ti:Sa laser as a self-reference for ion-trap experiments with a 40Ca+ ion

In this study, we report on the stabilization of a continuous-wave Ti:Sa laser to an optical frequency comb. The laser is emitting at 866 nm to address one of the transitions required for Doppler cooling of a single ⁴⁰Ca⁺ ion in a linear Paul trap (²D_3/2 ↔P1/22). The stabilized Ti:Sa laser is utilized to calibrate an ultra-accurate wavelength meter. We certify this self-reference laser source by comparing the results from monitoring the laser-cooled ⁴⁰Ca⁺ ion in the linear Paul trap, with those obtained when a HeNe laser is used for calibration. The use of this self-reference is compatible with the simultaneous use of the comb for precision spectroscopy in the same ion-trap experiment.

Coherent manipulation of an Andreev spin qubit

Two promising architectures for solid-state quantum information processing are based on electron spins electrostatically confined in semiconductor quantum dots and the collective electrodynamic modes of superconducting circuits. Superconducting electrodynamic qubits involve macroscopic numbers of electrons and offer the advantage of larger coupling, whereas semiconductor spin qubits involve individual electrons trapped in microscopic volumes but are more difficult to link. We combined beneficial aspects of both platforms in the Andreev spin qubit: the spin degree of freedom of an electronic quasiparticle trapped in the supercurrent-carrying Andreev levels of a Josephson semiconductor nanowire. We performed coherent spin manipulation by combining single-shot circuit-quantum-electrodynamics readout and spin-flipping Raman transitions and found a spin-flip time T _S = 17 microseconds and a spin coherence time T _2E = 52 nanoseconds. These results herald a regime of supercurrent-mediated coherent spin-photon coupling at the single-quantum level.

Low Field Nano-NMR via Three-Level System Control

Conventional control strategies for nitrogen-vacancy centers in quantum sensing are based on a two-level model of their triplet ground state. However, this approach fails in regimes of weak bias magnetic fields or strong microwave pulses, as we demonstrate. To overcome this limitation, we propose a novel control sequence that exploits all three levels by addressing a hidden Raman configuration with microwave pulses tuned to the zero-field transition. We report excellent performance in typical dynamical decoupling sequences, opening up the possibility for nano-NMR operation in low field environments.

Publisher's Note: Driven Open Quantum Systems and Floquet Stroboscopic Dynamics [Phys. Rev. Lett. 117, 250401 (2016)]

This corrects the article DOI: 10.1103/PhysRevLett.117.250401.

Driven Open Quantum Systems and Floquet Stroboscopic Dynamics

We provide an analytic solution to the problem of system-bath dynamics under the effect of high-frequency driving that has applications in a large class of settings, such as driven-dissipative many-body systems. Our method relies on discrete symmetries of the system-bath Hamiltonian and provides the time evolution operator of the full system, including bath degrees of freedom, without weak-coupling or Markovian assumptions. An interpretation of the solution in terms of the stroboscopic evolution of a family of observables under the influence of an effective static Hamiltonian is proposed, which constitutes a flexible simulation procedure of nontrivial Hamiltonians. We instantiate the result with the study of the spin-boson model with time-dependent tunneling amplitude. We analyze the class of Hamiltonians that may be stroboscopically accessed for this example and illustrate the dynamics of system and bath degrees of freedom.

Pulsed laser cooling for cavity optomechanical resonators

A pulsed cooling scheme for optomechanical systems is presented that is capable of cooling at much faster rates, shorter overall cooling times, and for a wider set of experimental scenarios than is possible by conventional methods. The proposed scheme can be implemented for both strongly and weakly coupled optomechanical systems in both weakly and highly dissipative cavities. We study analytically its underlying working mechanism, which is based on interferometric control of optomechanical interactions, and we demonstrate its efficiency with pulse sequences that are obtained by using methods from optimal control. The short time in which our scheme approaches the optomechanical ground state allows for a significant relaxation of current experimental constraints. Finally, the framework presented here can be used to create a rich variety of optomechanical interactions and hence offers a novel, readily available toolbox for fast optomechanical quantum control.

Fast and robust laser cooling of trapped systems

We present a robust and fast laser cooling scheme suitable for trapped ions, atoms, or cantilevers. Based on quantum interference, generated by a special laser configuration, it is able to rapidly cool the system such that the final phonon occupation vanishes to zeroth order in the Lamb-Dicke parameter in contrast to existing cooling schemes. Furthermore, it is robust under conditions of fluctuating laser intensity and frequency, thus making it a viable candidate for experimental applications.