284 research outputs found
Crystalline optical cavity at 4 K with thermal noise limited instability and ultralow drift
Crystalline optical cavities are the foundation of today's state-of-the-art
ultrastable lasers. Building on our previous silicon cavity effort, we now
achieve the fundamental thermal noise-limited stability for a 6 cm long silicon
cavity cooled to 4 Kelvin, reaching from 0.8 to 80 seconds.
We also report for the first time a clear linear dependence of the cavity
frequency drift on the incident optical power. The lowest fractional frequency
drift of /s is attained at a transmitted power of 40 nW, with
an extrapolated drift approaching zero in the absence of optical power. These
demonstrations provide a promising direction to reach a new performance domain
for stable lasers, with stability better than and fractional
linear drift below /s
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
A Conceptual Model for a Universal Severity of Emergency Report (USER): An Example in Aviation
In emergency situations, it is important that information be communicated quickly, concisely, and efficiently. Breakdowns can occur when the receiver of the emergency call does not fully understand the information that the person is sending. The purpose of this paper is to present a new model for enhancing communication between the sender and receiver in emergency situations. The Universal Severity of Emergency Report (USER) is a model designed to be used in emergency situations and convey more information about the current state of the person declaring the emergency than is currently offered by emergency communication channels. USER provides three key pieces of vital information: severity of the situation, capabilities of the sender, and ability to communicate. Severity identifies the level of the emergency on a scale of 1, 2, or 3. Capabilities use the colors white, yellow, and red to indicate the current self-determined capabilities of the individual. Communicate notifies the receiver if the individual is able to communicate or is unable to communicate. This paper presents this concept in an aviation context, but USER has the potential to be used in any number of industries, including medical, military, shipping, transportation, space flight, and law enforcement
Realizing spin squeezing with Rydberg interactions in a programmable optical clock
Neutral-atom arrays trapped in optical potentials are a powerful platform for
studying quantum physics, combining precise single-particle control and
detection with a range of tunable entangling interactions. For example, these
capabilities have been leveraged for state-of-the-art frequency metrology as
well as microscopic studies of entangled many-particle states. In this work, we
combine these applications to realize spin squeezing - a widely studied
operation for producing metrologically useful entanglement - in an optical
atomic clock based on a programmable array of interacting optical qubits. In
this first demonstration of Rydberg-mediated squeezing with a neutral-atom
optical clock, we generate states that have almost 4 dB of metrological gain.
Additionally, we perform a synchronous frequency comparison between independent
squeezed states and observe a fractional frequency stability of at one-second averaging time, which is 1.94(1) dB below the standard
quantum limit, and reaches a fractional precision at the level
during a half-hour measurement. We further leverage the programmable control
afforded by optical tweezer arrays to apply local phase shifts in order to
explore spin squeezing in measurements that operate beyond the relative
coherence time with the optical local oscillator. The realization of this
spin-squeezing protocol in a programmable atom-array clock opens the door to a
wide range of quantum-information inspired techniques for optimal phase
estimation and Heisenberg-limited optical atomic clocks.Comment: 13 pages, 4 figures; Supplementary Informatio
A tweezer clock with half-minute atomic coherence at optical frequencies and high relative stability
The preparation of large, low-entropy, highly coherent ensembles of identical
quantum systems is foundational for many studies in quantum metrology,
simulation, and information. Here, we realize these features by leveraging the
favorable properties of tweezer-trapped alkaline-earth atoms while introducing
a new, hybrid approach to tailoring optical potentials that balances
scalability, high-fidelity state preparation, site-resolved readout, and
preservation of atomic coherence. With this approach, we achieve trapping and
optical clock excited-state lifetimes exceeding seconds in ensembles of
approximately atoms. This leads to half-minute-scale atomic coherence
on an optical clock transition, corresponding to quality factors well in excess
of . These coherence times and atom numbers reduce the effect of
quantum projection noise to a level that is on par with leading atomic systems,
yielding a relative fractional frequency stability of
for synchronous clock comparisons
between sub-ensembles within the tweezer array. When further combined with the
microscopic control and readout available in this system, these results pave
the way towards long-lived engineered entanglement on an optical clock
transition in tailored atom arrays.Comment: 11 pages, 5 figures (main text); 17 pages, 7 figures (supplemental
materials
Crystalline optical cavity at 4 K with thermal-noise-limited instability and ultralow drift
Crystalline optical cavities are the foundation of today’s state-of-the-art ultrastable lasers. Building on our previous silicon cavity effort, we now achieve the fundamental thermal-noise-limited stability for a 6 cm long silicon cavity cooled to 4 K, reaching 6.5×10−17 from 0.8 s to 80 s. We also report for the first time, to the best of our knowledge, a clear linear dependence of the cavity frequency drift on incident optical power. The lowest fractional frequency drift of −3×10−19/s is attained at a transmitted power of 40 nW, with an extrapolated drift approaching zero in the absence of optical power. These demonstrations provide a promising direction to reach a new performance domain for stable lasers, with stability better than 1×10−17 and fractional linear drift below 1×10−19/s
Precision Metrology Meets Cosmology: Improved Constraints on Ultralight Dark Matter from Atom-Cavity Frequency Comparisons
We conduct frequency comparisons between a state-of-the-art strontium optical
lattice clock, a cryogenic crystalline silicon cavity, and a hydrogen maser to
set new bounds on the coupling of ultralight dark matter to Standard Model
particles and fields in the mass range of eV. The key
advantage of this two-part ratio comparison is the differential sensitivities
to time variation of both the fine-structure constant and the electron mass,
achieving a substantially improved limit on the moduli of ultralight dark
matter, particularly at higher masses than typical atomic spectroscopic
results. Furthermore, we demonstrate an extension of the search range to even
higher masses by use of dynamical decoupling techniques. These results
highlight the importance of using the best performing atomic clocks for
fundamental physics applications as all-optical timescales are increasingly
integrated with, and will eventually supplant, existing microwave timescales.Comment: 11 pages, 10 figure
Disentangling Pauli blocking of atomic decay from cooperative radiation and atomic motion in a 2D Fermi gas
The observation of Pauli blocking of atomic spontaneous decay via direct measurements of the atomic population requires the use of long-lived atomic gases where quantum statistics, atom recoil and cooperative radiative processes are all relevant. We develop a theoretical framework capable of simultaneously accounting for all these effects in a regime where prior theoretical approaches based on semi-classical non-interacting or interacting frozen atom approximations fail. We apply it to atoms in a single 2D pancake or arrays of pancakes featuring an effective A level structure (one excited and two degenerate ground states). We identify a parameter window in which a factor of two extension in the atomic lifetime clearly attributable to Pauli blocking should be experimentally observable in deeply degenerate gases with~103 atoms. Our predictions are supported by observation of a number-dependent excited state decay rate on the 1S0 - 3P1 transition in 87Sr atoms.Physic
Maternal–Fetal Microtransfusions and HIV-1 Mother-to-Child Transmission in Malawi
Background: Between 25% and 35% of infants born to HIV-infected mothers become HIV-1 infected. One potential route of mother-to-child transmission (MTCT) could be through a breakdown in the placental barrier (i.e., maternal–fetal microtransfusions). Methods and Findings: Placental alkaline phosphatase (PLAP) is a 130-kD maternal enzyme that cannot cross the intact placental barrier. We measured PLAP activity in umbilical vein serum as an indicator of maternal–fetal microtransfusion, and related this to the risk of HIV-1 MTCT. A case-cohort study was conducted of 149 women randomly selected from a cohort of HIV-1-infected pregnant Malawians; these women served as a reference group for 36 cases of in utero MTCT and 43 cases of intrapartum (IP) MTCT. Cord PLAP activity was measured with an immunocatalytic assay. Infant HIV status was determined by real-time PCR. The association between cord PLAP activity and HIV-1 MTCT was measured with logistic regression using generalized estimating equations. Among vaginal deliveries, PLAP was associated with IP MTCT (risk ratio, 2.25 per ng/ml PLAP; 95% confidence interval, 0.95–5.32) but not in utero MTCT. In a multivariable model adjusted for HIV-1 RNA load, chorioamnionitis, and self-reported fever, the risk of IP MTCT almost tripled for every increase in cord PLAP activity (risk ratio, 2.87; 95% confidence interval, 1.05–7.83). Conclusion: These results suggest that during vaginal deliveries, placental microtransfusions are a risk factor for IP HIV-1 MTCT. Future studies are needed to identify factors that increase the risk for microtransfusions in order to prevent IP HIV-1 MTCT
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