54 research outputs found
Recommended from our members
Ultracold Collisions and Fundamental Physics with Strontium
The success of strontium-based optical lattice clocks in the last five years has led to a recommendation by BIPM of strontium as a future standard of frequency and time. Due to the excellent agreement between three international labs, the strontium optical clock transition is the best agreed-upon optical frequency to date. We use the international optical clock data to limit present-day drift of fundamental constants and their coupling to the ambient gravitational potential. Strontium lattice clocks are still making rapid progress and promise a large signal-to-noise improvement over single-ion-based frequency standards by employing O(104) atoms. Reaching quantum-projection-noise limited measurement requires a careful study and control of the many-body interactions in the system. We measure interactions between ultracold fermions at the 10-17 level and relate them to s-wave collisions due to a loss of indistinguishability during the spectroscopic process. This new understanding of the many-body effects will increase the precision of current optical lattice clock systems and can lead to the accuracy level that has so far been pioneered only in single particle (trapped ion) systems. A second generation strontium system is used to control ultracold interactions in an otherwise ideal gas of bosonic 88Sr via the optical Feshbach resonance effect. These new measurement and control capabilities pave the way to reach atomic shot-noise limited optical clock performance without detrimental effects from large atom numbers
Site-resolved imaging of a fermionic Mott insulator
The complexity of quantum many-body systems originates from the interplay of
strong interactions, quantum statistics, and the large number of
quantum-mechanical degrees of freedom. Probing these systems on a microscopic
level with single-site resolution offers important insights. Here we report
site-resolved imaging of two-component fermionic Mott insulators, metals, and
band insulators using ultracold atoms in a square lattice. For strong repulsive
interactions we observe two-dimensional Mott insulators containing over 400
atoms. For intermediate interactions, we observe a coexistence of phases. From
comparison to theory we find trap-averaged entropies per particle of
. In the band-insulator we find local entropies as low as
. Access to local observables will aid the understanding
of fermionic many-body systems in regimes inaccessible by modern theoretical
methods.Comment: 6+7 page
Computational Capabilities and Compiler Development for Neutral Atom Quantum Processors: Connecting Tool Developers and Hardware Experts
Neutral Atom Quantum Computing (NAQC) emerges as a promising hardware
platform primarily due to its long coherence times and scalability.
Additionally, NAQC offers computational advantages encompassing potential
long-range connectivity, native multi-qubit gate support, and the ability to
physically rearrange qubits with high fidelity. However, for the successful
operation of a NAQC processor, one additionally requires new software tools to
translate high-level algorithmic descriptions into a hardware executable
representation, taking maximal advantage of the hardware capabilities.
Realizing new software tools requires a close connection between tool
developers and hardware experts to ensure that the corresponding software tools
obey the corresponding physical constraints. This work aims to provide a basis
to establish this connection by investigating the broad spectrum of
capabilities intrinsic to the NAQC platform and its implications on the
compilation process. To this end, we first review the physical background of
NAQC and derive how it affects the overall compilation process by formulating
suitable constraints and figures of merit. We then provide a summary of the
compilation process and discuss currently available software tools in this
overview. Finally, we present selected case studies and employ the discussed
figures of merit to evaluate the different capabilities of NAQC and compare
them between two hardware setups.Comment: 32 pages, 13 figures, 2 table
Systematic study of the Sr clock transition in an optical lattice
With ultracold Sr confined in a magic wavelength optical lattice, we
present the most precise study (2.8 Hz statistical uncertainty) to-date of the
- optical clock transition with a detailed analysis of
systematic shifts (20 Hz uncertainty) in the absolute frequency measurement of
429 228 004 229 867 Hz. The high resolution permits an investigation of the
optical lattice motional sideband structure. The local oscillator for this
optical atomic clock is a stable diode laser with its Hz-level linewidth
characterized across the optical spectrum using a femtosecond frequency comb.Comment: 4 pages, 4 figures, 1 tabl
Optical atomic coherence at the one-second time scale
Highest resolution laser spectroscopy has generally been limited to single
trapped ion systems due to rapid decoherence which plagues neutral atom
ensembles. Here, precision spectroscopy of ultracold neutral atoms confined in
a trapping potential shows superior optical coherence without any deleterious
effects from motional degrees of freedom, revealing optical resonance
linewidths at the hertz level with an excellent signal to noise ratio. The
resonance quality factor of 2.4 x 10^{14} is the highest ever recovered in any
form of coherent spectroscopy. The spectral resolution permits direct
observation of the breaking of nuclear spin degeneracy for the 1S0 and 3P0
optical clock states of 87Sr under a small magnetic bias field. This optical
NMR-like approach allows an accurate measurement of the differential Lande
g-factor between the two states. The optical atomic coherence demonstrated for
collective excitation of a large number of atoms will have a strong impact on
quantum measurement and precision frequency metrology.Comment: in press (2006
Geodesy and metrology with a transportable optical clock
partially_open24openGrotti, Jacopo; Koller, Silvio; Vogt, Stefan; Häfner, Sebastian; Sterr, Uwe; Lisdat, Christian; Denker, Heiner; Voigt, Christian; Timmen, Ludger; Rolland, Antoine; Baynes, Fred N.; Margolis, Helen S.; Zampaolo, Michel; Thoumany, Pierre; Pizzocaro, Marco; Rauf, Benjamin; Bregolin, Filippo; Tampellini, Anna; Barbieri, Piero; Zucco, Massimo; Costanzo, Giovanni A.; Clivati, Cecilia; Levi, Filippo; Calonico, DavideGrotti, Jacopo; Koller, Silvio; Vogt, Stefan; Häfner, Sebastian; Sterr, Uwe; Lisdat, Christian; Denker, Heiner; Voigt, Christian; Timmen, Ludger; Rolland, Antoine; Baynes, Fred N.; Margolis, Helen S.; Zampaolo, Michel; Thoumany, Pierre; Pizzocaro, Marco; Rauf, Benjamin; Bregolin, Filippo; Tampellini, Anna; Barbieri, Piero; Zucco, Massimo; Costanzo, Giovanni A.; Clivati, Cecilia; Levi, Filippo; Calonico, David
Feshbach resonances and mesoscopic phase separation near a quantum critical point in multiband FeAs-based superconductors
High Tc superconductivity in FeAs-based multilayers (pnictides), evading
temperature decoherence effects in a quantum condensate, is assigned to a
Feshbach resonance (called also shape resonance) in the exchange-like interband
pairing. The resonance is switched on by tuning the chemical potential at an
electronic topological transition (ETT) near a band edge, where the Fermi
surface topology of one of the subbands changes from 1D to 2D topology. We show
that the tuning is realized by changing i) the misfit strain between the
superconducting planes and the spacers ii) the charge density and iii) the
disorder. The system is at the verge of a catastrophe i.e. near a structural
and magnetic phase transition associated with the stripes (analogous to the 1/8
stripe phase in cuprates) order to disorder phase transition. Fine tuning of
both the chemical potential and the disorder pushes the critical temperature Ts
of this phase transition to zero giving a quantum critical point. Here the
quantum lattice and magnetic fluctuations promote the Feshbach resonance of the
exchange-like anisotropic pairing. This superconducting phase that resists to
the attacks of temperature is shown to be controlled by the interplay of the
hopping energy between stripes and the quantum fluctuations. The
superconducting gaps in the multiple Fermi surface spots reported by the recent
ARPES experiment of D. V. Evtushinsky et al. arXiv:0809.4455 are shown to
support the Feshbach scenario.Comment: 31 pages, 7 figure
- …