Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session K09: Quantum Thermodynamics and Non-equiibrium Dynamics |
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Sponsoring Units: DQI Chair: Hossein Sadeghpour, Harvard College Observatory Room: Grand H |
Wednesday, May 30, 2018 2:00PM - 2:30PM |
K09.00001: Quantum fluctuation theorems go Quantum Computers Invited Speaker: Sebastian Deffner Near term quantum hardware promises unprecedented computational advantage. Crucial in its development is the characterization and minimization of computational errors. We will review recent developments in informational quantum fluctuation theorems and propose the use of them to characterize the performance of quantum annealers. We will see that this versatile tool provides simple means to determine whether the quantum dynamics are unital, unitary, and adiabatic, or whether the system is prone to thermal noise. Our proposal was experimentally tested on two generations of the DWave machine, which illustrates the sensitivity of the fluctuation theorem to the smallest aberrations from ideal annealing.\\ \\ References: \begin{itemize} \item[[1]] Kafri and Deffner, Phys. Rev. A \textbf{86}, 044302 (2012) \item[[2]] Gardas and Deffner, arXiv:1801.06925 \end{itemize} [Preview Abstract] |
Wednesday, May 30, 2018 2:30PM - 3:00PM |
K09.00002: Thermodynamics experiments on single-electron circuits and superconducting qubits Invited Speaker: Jukka Pekola Thermodynamics of quantum systems and processes has attracted increased attention in the past years due to the fundamental interest in physics of small systems and the possibilities provided by advanced fabrication and measurement techniques. In particular time-resolved detection of single electrons and the possibility to directly measure heat via sensitive and fast thermometry in low temperature nanostructures have opened a new avenue in stochastic thermodynamics. Advances in superconducting qubit research provide further new opportunities in quantum thermodynamics. Here I review our experiments on non-equilibrium fluctuation relations, on externally controlled and autonomous Maxwell’s demons and our first steps in using superconducting qubits as working substance in quantum heat engines and refrigerators. [Preview Abstract] |
Wednesday, May 30, 2018 3:00PM - 3:30PM |
K09.00003: Quantum Double-Well Dynamics of Trapped Ion Crystals near a Structural Phase Transition Invited Speaker: Paul C Haljan In a linear radio-frequency Paul trap, relaxing the transverse confinement beyond a critical value will cause laser-cooled, trapped ions to undergo a symmetry–breaking structural transition from a linear to a two-dimensional zigzag configuration. I will discuss our current investigations of dynamics near this linear-zigzag transition at temperatures corresponding to a few quanta or less of thermal energy in the vibrations of the ion array. The second-order nature of the ideal linear-zigzag transition, and the resulting symmetric double-well potential that develops as the critical point for the transition is crossed, offer the possibility to explore a variety of quantum effects, in particular tunneling phenomena near the critical point. Using Raman sideband techniques, we probe spectroscopically the shape of the double well and assess the decoherence near the transition for our system of Yb$^+$ ions in a four-rod linear Paul trap. We are ultimately interested to see whether superposition states of the zig and zag symmetry-broken configurations can be prepared, and how the decoherence of such states depends on the number of ions. [Preview Abstract] |
Wednesday, May 30, 2018 3:30PM - 4:00PM |
K09.00004: Atomic Friction and Dynamics of Topological Defects in Ion Coulomb Crystals Invited Speaker: Tanja Mehlstaubler Topological defects in ion Coulomb crystals (kinks) have been proposed for studies of quantum-mechanical effects with solitons and as carriers of quantum information. Defects form when a symmetry breaking phase transition is crossed nonadiabatically and the finite speed of information prevents different regions from coordinating the choice of the symmetry broken state. Where such local choices are incompatible, defects will form with densities predicted to follow a power law scaling in the rate of the transition. The importance of this Kibble-Zurek mechanism (KZM) ranges from cosmology to condensed matter. In inhomogeneous systems, the propagation of the critical front enhances the role of causality and steepens scaling of defect density with the transition rate. We use laser-cooled trapped ions in a harmonic trap to produce stable topological defects and demonstrate scaling with the transition rate across the linear to zigzag phase. Implementing mass defects and electric fields we demonstrated first steps towards a controlled kink soliton preparation and manipulation for studies of nonlinear physics in ion Coulomb crystals. Based on these findings we study the dynamics of topological defects and use them to emulate nanofriction of two atomically flat layers with back-action. With the help of phonon mode spectroscopy and high-resolution imaging we show that an ion Coulomb crystal with a defect exhibits a sticking-to-sliding transition with Aubry-type signatures. We demonstrate the measurement of the soft vibrational mode driving the transition and the order parameter, that quantifies the symmetry-breaking of the crystal configuration. Numerically we find that the soft mode frequency and the order parameter exhibit critical scaling near the transition. This model system can be used to investigate the tribological behaviour of self-organized structures in the classical and in the quantum regime. [Preview Abstract] |
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