1,847 research outputs found
Engineering spin squeezing in a 3D optical lattice with interacting spin-orbit-coupled fermions
One of the most important tasks in modern quantum science is to coherently
control and entangle many-body systems, and to subsequently use these systems
to realize powerful quantum technologies such as quantum-enhanced sensors.
However, many-body entangled states are difficult to prepare and preserve since
internal dynamics and external noise rapidly degrade any useful entanglement.
Here, we introduce a protocol that counterintuitively exploits inhomogeneities,
a typical source of dephasing in a many-body system, in combination with
interactions to generate metrologically useful and robust many-body entangled
states. Motivated by current limitations in state-of-the-art three-dimensional
(3D) optical lattice clocks (OLCs) operating at quantum degeneracy, we use
local interactions in a Hubbard model with spin-orbit coupling to achieve a
spin-locking effect. In addition to prolonging inter-particle spin coherence,
spin-locking transforms the dephasing effect of spin-orbit coupling into a
collective spin-squeezing process that can be further enhanced by applying a
modulated drive. Our protocol is fully compatible with state-of-the-art 3D OLC
interrogation schemes and may be used to improve their sensitivity, which is
currently limited by the intrinsic quantum noise of independent atoms. We
demonstrate that even with realistic experimental imperfections, our protocol
may generate -- dB of spin squeezing in second with
-- atoms. This capability allows OLCs to enter a new era of
quantum enhanced sensing using correlated quantum states of driven
non-equilibrium systems.Comment: 20 pages, 12 figure
High-fidelity imaging of a band insulator in a three-dimensional optical lattice clock
We report on the observation of a high-density, band insulating state in a
three-dimensional optical lattice clock. Filled with a nuclear-spin polarized
degenerate Fermi gas of 87Sr, the 3D lattice has one atom per site in the
ground motional state, thus guarding against frequency shifts due to contact
interactions. At this high density where the average distance between atoms is
comparable to the probe wavelength, standard imaging techniques suffer from
large systematic errors. To spatially probe frequency shifts in the clock and
measure thermodynamic properties of this system, accurate imaging techniques at
high optical depths are required. Using a combination of highly saturated
fluorescence and absorption imaging, we confirm the density distribution in our
3D optical lattice in agreement with a single spin band insulating state.
Combining our clock platform with this high filling fraction opens the door to
studying new classes of long-lived, many-body states arising from dipolar
interactions.Comment: 10 pages, 8 figure
Observation of mHz-level cooperative Lamb shifts in an optical atomic clock
We report on the direct observation of resonant electric dipole-dipole
interactions in a cubic array of atoms in the many-excitation limit. The
interactions, mediated by single-atom couplings to the shared electromagnetic
vacuum, are shown to produce spatially-dependent cooperative Lamb shifts when
spectroscopically interrogating the mHz-wide optical clock transition in
strontium-87. We show that the ensemble-averaged shifts can be suppressed below
the level of evaluated systematic uncertainties for state-of-the-art optical
atomic clocks. Additionally, we demonstrate that excitation of the atomic
dipoles near a Bragg angle can enhance these effects by nearly an order of
magnitude compared to non-resonant geometries. Given the remarkable precision
of frequency measurements and the high accuracy of the modeled response, our
work demonstrates that such a clock is a novel platform for studies of the
quantum many-body physics of spins with long-range interactions mediated by
propagating photons
Cold collisions of OH and Rb. I: the free collision
We have calculated elastic and state-resolved inelastic cross sections for
cold and ultracold collisions in the Rb() + OH() system,
including fine-structure and hyperfine effects. We have developed a new set of
five potential energy surfaces for Rb-OH() from high-level {\em ab
initio} electronic structure calculations, which exhibit conical intersections
between covalent and ion-pair states. The surfaces are transformed to a
quasidiabatic representation. The collision problem is expanded in a set of
channels suitable for handling the system in the presence of electric and/or
magnetic fields, although we consider the zero-field limit in this work.
Because of the large number of scattering channels involved, we propose and
make use of suitable approximations. To account for the hyperfine structure of
both collision partners in the short-range region we develop a
frame-transformation procedure which includes most of the hyperfine
Hamiltonian. Scattering cross sections on the order of cm are
predicted for temperatures typical of Stark decelerators. We also conclude that
spin orientation of the partners is completely disrupted during the collision.
Implications for both sympathetic cooling of OH molecules in an environment of
ultracold Rb atoms and experimental observability of the collisions are
discussed.Comment: 20 pages, 16 figure
The formation of homogentisate in the biosynthesis of tocopherol and plastoquinone in spinach chloroplasts
Homogentisate is the precursor in the biosynthesis of -tocopherol and plastoquinone-9 in chloroplasts. It is formed of 4-hydroxyphenylpyruvate of the shikimate pathway by the 4-hydroxyphenylpyruvate dioxygenase. In experiments with spinach the dioxygenase was shown to be localized predominatedly in the chloroplasts. Envelope membranes exhibit the highest specific activity, however, because of the high stromal portion of chloroplasts, 60–80% of the total activity is housed in the stroma. The incorporation of 4-hydroxyphenylpyruvate into 2-methyl-6-phytylquinol as the first intermediate in the tocopherol synthesis by the two-step-reaction: 4-Hydroxyphenylpyruvate Homogentisate 2-Methyl-6-phytylquinol was demonstrated by using envelope membranes. Homogentisate originates directly from 4-hydroxyphenylpyruvate of the shikimate pathway. Additionally, a bypass exists in chloroplasts which forms 4-hydroxyphenylpyruvate from tyrosine by an L-amino-acid oxidase of the thylakoids and in peroxisomes by a transaminase reaction. Former results about the dioxygenase in peroxisomes were verified
Inversion of Randomly Corrugated Surfaces Structure from Atom Scattering Data
The Sudden Approximation is applied to invert structural data on randomly
corrugated surfaces from inert atom scattering intensities. Several expressions
relating experimental observables to surface statistical features are derived.
The results suggest that atom (and in particular He) scattering can be used
profitably to study hitherto unexplored forms of complex surface disorder.Comment: 10 pages, no figures. Related papers available at
http://neon.cchem.berkeley.edu/~dan
Long beating wavelength in the Schwarz-Hora effect
Thirty years ago, H.Schwarz has attempted to modulate an electron beam with
optical frequency. When a 50-keV electron beam crossed a thin crystalline
dielectric film illuminated with laser light, electrons produced the
electron-diffraction pattern not only at a fluorescent target but also at a
nonfluorescent target. In the latter case the pattern was of the same color as
the laser light (the Schwarz-Hora effect). This effect was discussed
extensively in the early 1970s. However, since 1972 no reports on the results
of further attempts to repeat those experiments in other groups have appeared,
while the failures of the initial such attempts have been explained by Schwarz.
The analysis of the literature shows there are several unresolved up to now
contradictions between the theory and the Schwarz experiments. In this work we
consider the interpretation of the long-wavelength spatial beating of the
Schwarz-Hora radiation. A more accurate expression for the spatial period has
been obtained, taking into account the mode structure of the laser field within
the dielectric film. It is shown that the discrepancy of more than 10% between
the experimental and theoretical results for the spatial period cannot be
reduced by using the existing quantum models that consider a collimated
electron beam.Comment: 3 pages, RevTe
- …