73 research outputs found
Coherent storage and manipulation of broadband photons via dynamically controlled Autler-Townes splitting
The coherent control of light with matter, enabling storage and manipulation
of optical signals, was revolutionized by electromagnetically induced
transparency (EIT), which is a quantum interference effect. For strong
electromagnetic fields that induce a wide transparency band, this quantum
interference vanishes, giving rise to the well-known phenomenon of
Autler-Townes splitting (ATS). To date, it is an open question whether ATS can
be directly leveraged for coherent control as more than just a case of "bad"
EIT. Here, we establish a protocol showing that dynamically controlled
absorption of light in the ATS regime mediates coherent storage and
manipulation that is inherently suitable for efficient broadband quantum memory
and processing devices. We experimentally demonstrate this protocol by storing
and manipulating nanoseconds-long optical pulses through a collective spin
state of laser-cooled Rb atoms for up to a microsecond. Furthermore, we show
that our approach substantially relaxes the technical requirements intrinsic to
established memory schemes, rendering it suitable for broad range of platforms
with applications to quantum information processing, high-precision
spectroscopy, and metrology.Comment: 14 pages with 6 figures; 3 pages supplementary info with 2
supplementary figure
Complete unitary qutrit control in ultracold atoms
Physical quantum systems are commonly composed of more than two levels and
offer the capacity to encode information in higher-dimensional spaces beyond
the qubit, starting with the three-level qutrit. Here, we encode neutral-atom
qutrits in an ensemble of ultracold Rb and demonstrate arbitrary
single-qutrit SU(3) gates. We generate a full set of gates using only two
resonant microwave tones, including synthesizing a gate that effects a direct
coupling between the two disconnected levels in the three-level
-scheme. Using two different gate sets, we implement and characterize
the Walsh-Hadamard Fourier transform, and find similar final-state fidelity and
purity from both approaches. This work establishes the ultracold neutral-atom
qutrit as a promising platform for qutrit-based quantum information processing,
extensions to -dimensional qudits, and explorations in multilevel quantum
state manipulations with nontrivial geometric phases.Comment: 5 pages and 4 figures, plus 7 pages supplementary material. Updated
to published version, journal reference now include
Demonstration of Floquet engineered non-Abelian geometric phase for holonomic quantum computing
Holonomic quantum computing (HQC) functions by transporting an adiabatically
degenerate manifold of computational states around a closed loop in a
control-parameter space; this cyclic evolution results in a non-Abelian
geometric phase which may couple states within the manifold. Realizing the
required degeneracy is challenging, and typically requires auxiliary levels or
intermediate-level couplings. One potential way to circumvent this is through
Floquet engineering, where the periodic driving of a nondegenerate Hamiltonian
leads to degenerate Floquet bands, and subsequently non-Abelian gauge
structures may emerge. Here we present an experiment in ultracold Rb
atoms where atomic spin states are dressed by modulated RF fields to induce
periodic driving of a family of Hamiltonians linked through a fully tuneable
parameter space. The adiabatic motion through this parameter space leads to the
holonomic evolution of the degenerate spin states in , characterized by
a non-Abelian connection. We study the holonomic transformations of spin
eigenstates in the presence of a background magnetic field, characterizing the
fidelity of these gate operations. Results indicate that while the Floquet
engineering technique removes the need for explicit degeneracies, it inherits
many of the same limitations present in degenerate systems
Longitudinal Research on Aging Drivers (LongROAD): study design and methods
Background:
As an important indicator of mobility, driving confers a host of social and health benefits to older adults. Despite the importance of safe mobility as the population ages, longitudinal data are lacking about the natural history and determinants of driving safety in older adults.
Methods:
The Longitudinal Research on Aging Drivers (LongROAD) project is a multisite prospective cohort study designed to generate empirical data for understanding the role of medical, behavioral, environmental and technological factors in driving safety during the process of aging.
Results:
A total of 2990 active drivers aged 65–79 years at baseline have been recruited through primary care clinics or health care systems in five study sites located in California, Colorado, Maryland, Michigan, and New York. Consented participants were assessed at baseline with standardized research protocols and instruments, including vehicle inspection, functional performance tests, and “brown-bag review” of medications. The primary vehicle of each participant was instrumented with a small data collection device that records detailed driving data whenever the vehicle is operating and detects when a participant is driving. Annual follow-up is being conducted for up to three years with a telephone questionnaire at 12 and 36 months and in-person assessment at 24 months. Medical records are reviewed annually to collect information on clinical diagnoses and healthcare utilization. Driving records, including crashes and violations, are collected annually from state motor vehicle departments. Pilot testing was conducted on 56 volunteers during March–May 2015. Recruitment and enrollment were completed between July 2015 and March 2017.
Conclusions:
Results of the LongROAD project will generate much-needed evidence for formulating public policy and developing intervention programs to maintain safe mobility while ensuring well-being for older adults
Investigating Mercury's Environment with the Two-Spacecraft BepiColombo Mission
The ESA-JAXA BepiColombo mission will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric dynamics at Mercury as well as their interactions with the solar wind, radiation, and interplanetary dust. Many scientific instruments onboard the two spacecraft will be completely, or partially devoted to study the near-space environment of Mercury as well as the complex processes that govern it. Many issues remain unsolved even after the MESSENGER mission that ended in 2015. The specific orbits of the two spacecraft, MPO and Mio, and the comprehensive scientific payload allow a wider range of scientific questions to be addressed than those that could be achieved by the individual instruments acting alone, or by previous missions. These joint observations are of key importance because many phenomena in Mercury's environment are highly temporally and spatially variable. Examples of possible coordinated observations are described in this article, analysing the required geometrical conditions, pointing, resolutions and operation timing of different BepiColombo instruments sensors.Peer reviewe
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