Atomic Physics

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Continuous real-time tracking of a quantum phase below the standard quantum limit (1809.08216v3)

Athreya Shankar, Graham P. Greve, Baochen Wu, James K. Thompson, Murray Holland

2018-09-21

We propose a scheme for continuously measuring the evolving quantum phase of a collective spin composed of pseudospins. Quantum non-demolition measurements of a lossy cavity mode interacting with an atomic ensemble are used to directly probe the phase of the collective atomic spin without converting it into a population difference. Unlike traditional Ramsey measurement sequences, our scheme allows for real-time tracking of time-varying signals. As a bonus, spin-squeezed states develop naturally, providing real-time phase estimation significantly more precise than the standard quantum limit of radians.

Resonant single-photon double ionization driven by combined intra- and interatomic electron correlations (1906.08123v1)

A. Eckey, A. B. Voitkiv, C. Müller

2019-06-19

Double ionization of an atom by single-photon absorption in the presence of a neighbouring atom is studied. The latter is, first, resonantly photoexcited and, afterwards, transfers the excitation energy radiationlessly to the other atom, leading to its double ionization. The process relies on the combined effect of interatomic and intraatomic electron correlations. It can dominate over the direct double photoionization by several orders of magnitude at interatomic distances up to few nanometers. The relative position of the neighbouring atom is shown to exert a characteristic influence on the angular distribution of emitted electrons.

Quantum dynamics of atomic Rydberg excitation in strong laser fields (1906.08093v1)

Shilin Hu, Xiaolei Hao, Hang Lv, Mingqing Liu, Tianxiang Yang, Haifeng Xu, Mingxing Jin, Dajun Ding, Qianguang Li, Weidong Li, Wilhelm Becker, Jing Chen

2019-06-19

Neutral atoms have been observed to survive intense laser pulses in high Rydberg states with surprisingly large probability. Only with this Rydberg-state excitation (RSE) included is the picture of intense-laser-atom interaction complete. Various mechanisms have been proposed to explain the underlying physics. However, neither one can explain all the features observed in experiments and in time-dependent Schr"{o}dinger equation (TDSE) simulations. Here we propose a fully quantum-mechanical model based on the strong-field approximation (SFA). It well reproduces the intensity dependence of RSE obtained by the TDSE, which exhibits a series of modulated peaks. They are due to recapture of the liberated electron and the fact that the pertinent probability strongly depends on the position and the parity of the Rydberg state. We also present measurements of RSE in xenon at 800 nm, which display the peak structure consistent with the calculations.

Quantifying and controlling prethermal nonergodicity in interacting Floquet matter (1809.05554v4)

Kevin Singh, Cora J. Fujiwara, Zachary A. Geiger, Ethan Q. Simmons, Mikhail Lipatov, Alec Cao, Peter Dotti, Shankari V. Rajagopal, Ruwan Senaratne, Toshihiko Shimasaki, Markus Heyl, André Eckardt, David M. Weld

2018-09-14

The use of periodic driving for synthesizing many-body quantum states depends crucially on the existence of a prethermal regime, which exhibits drive-tunable properties while forestalling the effects of heating. This motivates the search for direct experimental probes of the underlying localized nonergodic nature of the wave function in this metastable regime. We report experiments on a many-body Floquet system consisting of atoms in an optical lattice subjected to ultrastrong sign-changing amplitude modulation. Using a double-quench protocol we measure an inverse participation ratio quantifying the degree of prethermal localization as a function of tunable drive parameters and interactions. We obtain a complete prethermal map of the drive-dependent properties of Floquet matter spanning four square decades of parameter space. Following the full time evolution, we observe sequential formation of two prethermal plateaux, interaction-driven ergodicity, and strongly frequency-dependent dynamics of long-time thermalization. The complete experimental control and quantitative characterization of prethermal Floquet matter demonstrated here opens a new frontier for probing far-from-equilibrium quantum statistical mechanics and new possibilities for dynamical quantum engineering.

Engineering Quantum States of Matter for Atomic Clocks in Shallow Optical Lattices (1903.02498v2)

Ross B. Hutson, Akihisa Goban, G. Edward Marti, Lindsay Sonderhouse, Christian Sanner, Jun Ye

2019-03-06

We investigate the effects of stimulated scattering of optical lattice photons on atomic coherence times in a state-of-the art optical lattice clock. Such scattering processes are found to limit the achievable coherence times to less than 12 s (corresponding to a quality factor of ), significantly shorter than the predicted 145(40) s lifetime of 's excited clock state. We suggest that shallow, state-independent optical lattices with increased lattice constants can give rise to sufficiently small lattice photon scattering and motional dephasing rates as to enable coherence times on the order of the clock transition's natural lifetime. Not only should this scheme be compatible with the relatively high atomic density associated with Fermi-degenerate gases in three-dimensional optical lattices, but we anticipate that certain properties of various quantum states of matter can be used to suppress dephasing due to tunneling.

Distance scaling and polarization of electric-field noise in a surface ion trap (1906.06489v2)

Da An, Clemens Matthiesen, Erik Urban, Hartmut Häffner

2019-06-15

We probe electric-field noise in a surface ion trap for ion-surface distances between 50 and 300 in the normal and planar directions. We find the noise distance dependence to scale as in our trap and a frequency dependence which is consistent with noise. Simulations of the electric-field noise specific to our trap geometry provide evidence that we are not limited by technical noise sources. Our distance scaling data is consistent with a noise correlation length of about 100 at the trap surface, and we discuss how patch potentials of this size would be modified by the electrode geometry.

Blackbody radiation shift for the S--P optical clock transition in zinc and cadmium atoms (1906.07853v1)

Vladimir A. Dzuba, Andrei Derevianko

2019-06-19

Black-body radiation (BBR) shifts of clock transition in divalent atoms Cd and Zn are evaluated using accurate relativistic many-body techniques of atomic structure. Static polarizabilities of the clock levels and relevant electric-dipole matrix elements are computed. We also present a comparative overview of the BBR shifts in optical clocks based on neutral divalent atoms trapped in optical lattices.

Single-beam Zeeman slower and magneto-optical trap using a nanofabricated grating (1811.09180v3)

D. S. Barker, E. B. Norrgard, N. N. Klimov, J. A. Fedchak, J. Scherschligt, S. Eckel

2018-11-22

We demonstrate a compact (0.25 L) system for laser cooling and trapping atoms from a heated dispenser source. Our system uses a nanofabricated diffraction grating to generate a magneto-optical trap (MOT) using a single input laser beam. An aperture in the grating allows atoms from the dispenser to be loaded from behind the chip, increasing the interaction distance of atoms with the cooling light. To take full advantage of this increased distance, we extend the magnetic field gradient of the MOT to create a Zeeman slower. The MOT traps approximately Li atoms emitted from an effusive source with loading rates in excess of s. Our design is portable to a variety of atomic and molecular species and could be a principal component of miniaturized cold-atom-based technologies.

Atomic Resonant Single-Mode Squeezed Light from Four-Wave Mixing through Feedforward (1906.07666v1)

Saesun Kim, Alberto M. Marino

2019-06-18

Squeezed states of light have received renewed attention due to their applicability to quantum-enhanced sensing. To take full advantage of their reduced noise properties to enhance atomic-based sensors, it is necessary to generate narrowband near or on atomic resonance single-mode squeezed states of light. We have previously generated bright two-mode squeezed states of light, or twin beams, that can be tuned to resonance with the D1 line of Rb with a non-degenerate four-wave mixing (FWM) process in a double-lambda configuration in a Rb vapor cell. Here we report on the use of feedforward to transfer the amplitude quantum correlations present in the twin beams to a single beam for the generation of single-mode amplitude squeezed light. With this technique we obtain a single-mode squeezed state with a squeezing level of dB when it is tuned off-resonance and a level of dB when it is tuned on resonance with the D1 to transition of Rb.

Floquet engineering of optical lattices with spatial features and periodicity below the diffraction limit (1906.07646v1)

S. Subhankar, P. Bienias, P. Titum, T-C. Tsui, Y. Wang, A. V. Gorshkov, S. L. Rolston, J. V. Porto

2019-06-18

Floquet engineering or coherent time periodic driving of quantum systems has been successfully used to synthesize Hamiltonians with novel properties. In ultracold atomic systems, this has led to experimental realizations of artificial gauge fields, topological band structures, and observation of dynamical localization, to name just a few. Here we present a Floquet-based framework to stroboscopically engineer Hamiltonians with spatial features and periodicity below the diffraction limit of light used to create them by time-averaging over various configurations of a 1D optical Kronig-Penney (KP) lattice. The KP potential is a lattice of narrow subwavelength barriers spaced by half the optical wavelength () and arises from the non-linear optical response of the atomic dark state. Stroboscopic control over the strength and position of this lattice requires time-dependent adiabatic manipulation of the dark state spin composition. We investigate adiabaticity requirements and shape our time-dependent light fields to respect the requirements. We apply this framework to show that a -spaced lattice can be synthesized using realistic experimental parameters as an example, discuss mechanisms that limit lifetimes in these lattices, explore candidate systems and their limitations, and treat adiabatic loading into the ground band of these lattices.

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