81 research outputs found
Floquet Prethermalization in a Bose-Hubbard System
Periodic driving has emerged as a powerful tool in the quest to engineer new
and exotic quantum phases. While driven many-body systems are generically
expected to absorb energy indefinitely and reach an infinite-temperature state,
the rate of heating can be exponentially suppressed when the drive frequency is
large compared to the local energy scales of the system -- leading to
long-lived 'prethermal' regimes. In this work, we experimentally study a
bosonic cloud of ultracold atoms in a driven optical lattice and identify such
a prethermal regime in the Bose-Hubbard model. By measuring the energy
absorption of the cloud as the driving frequency is increased, we observe an
exponential-in-frequency reduction of the heating rate persisting over more
than 2 orders of magnitude. The tunability of the lattice potentials allows us
to explore one- and two-dimensional systems in a range of different interacting
regimes. Alongside the exponential decrease, the dependence of the heating rate
on the frequency displays features characteristic of the phase diagram of the
Bose-Hubbard model, whose understanding is additionally supported by numerical
simulations in one dimension. Our results show experimental evidence of the
phenomenon of Floquet prethermalization, and provide insight into the
characterization of heating for driven bosonic systems
A subradiant optical mirror formed by a single structured atomic layer
Efficient and versatile interfaces for the interaction of light with matter
are an essential cornerstone for quantum science. A fundamentally new avenue of
controlling light-matter interactions has been recently proposed based on the
rich interplay of photon-mediated dipole-dipole interactions in structured
subwavelength arrays of quantum emitters. Here we report on the direct
observation of the cooperative subradiant response of a two-dimensional (2d)
square array of atoms in an optical lattice. We observe a spectral narrowing of
the collective atomic response well below the quantum-limited decay of
individual atoms into free space. Through spatially resolved spectroscopic
measurements, we show that the array acts as an efficient mirror formed by only
a single monolayer of a few hundred atoms. By tuning the atom density in the
array and by changing the ordering of the particles, we are able to control the
cooperative response of the array and elucidate the interplay of spatial order
and dipolar interactions for the collective properties of the ensemble. Bloch
oscillations of the atoms out of the array enable us to dynamically control the
reflectivity of the atomic mirror. Our work demonstrates efficient optical
metamaterial engineering based on structured ensembles of atoms and paves the
way towards the controlled many-body physics with light and novel light-matter
interfaces at the single quantum level.Comment: 8 pages, 5 figures + 12 pages Supplementary Infomatio
Integrated tunneling sensor for nanoelectromechanical systems
Transducers based on quantum mechanical tunneling provide an extremely sensitive sensor principle, especially for nanoelectromechanical systems. For proper operation a gap between the electrodes of below 1nm is essential, requiring the use of structures with a mobile electrode. At such small distances, attractive van der Waals and capillary forces become sizable, possibly resulting in snap-in of the electrodes. The authors present a comprehensive analysis and evaluation of the interplay between the involved forces and identify requirements for the design of tunnelingsensors. Based on this analysis, a tunnelingsensor is fabricated by Si micromachiningtechnology and its proper operation is demonstrated
Scale up your In-Memory Accelerator: Leveraging Wireless-on-Chip Communication for AIMC-based CNN Inference
Analog In-Memory Computing (AIMC) is emerging as a disruptive paradigm for heterogeneous computing, potentially delivering orders of magnitude better peak performance and efficiency over traditional digital signal processing architectures on Matrix-Vector multiplication. However, to sustain this throughput in real-world applications, AIMC tiles must be supplied with data at very high bandwidth and low latency; this poses an unprecedented pressure on the on-chip communication infrastructure, which becomes the system's performance and efficiency bottleneck. In this context, the performance and plasticity of emerging on-chip wireless communication paradigms provide the required breakthrough to up-scale on-chip communication in large AIMC devices. This work presents a many-tile AIMC architecture with inter-tile wireless communication that integrates multiple heterogeneous computing clusters, embedding a mix of parallel RISC-V cores and AIMC tiles. We perform an extensive design space exploration of the proposed architecture and discuss the benefits of exploiting emerging on-chip communication technologies such as wireless transceivers in the millimeter-wave and terahertz band
ABSense: Sensing Electromagnetic Waves on Metasurfaces via Ambient Compilation of Full Absorption
Metasurfaces constitute effective media for manipulating and transforming
impinging EM waves. Related studies have explored a series of impactful MS
capabilities and applications in sectors such as wireless communications,
medical imaging and energy harvesting. A key-gap in the existing body of work
is that the attributes of the EM waves to-be-controlled (e.g., direction,
polarity, phase) are known in advance. The present work proposes a practical
solution to the EM wave sensing problem using the intelligent and networked MS
counterparts-the HyperSurfaces (HSFs), without requiring dedicated field
sensors. An nano-network embedded within the HSF iterates over the possible MS
configurations, finding the one that fully absorbs the impinging EM wave, hence
maximizing the energy distribution within the HSF. Using a distributed
consensus approach, the nano-network then matches the found configuration to
the most probable EM wave traits, via a static lookup table that can be created
during the HSF manufacturing. Realistic simulations demonstrate the potential
of the proposed scheme. Moreover, we show that the proposed workflow is the
first-of-its-kind embedded EM compiler, i.e., an autonomic HSF that can
translate high-level EM behavior objectives to the corresponding, low-level EM
actuation commands.Comment: Publication: Proceedings of ACM NANOCOM 2019. This work was funded by
the European Union via the Horizon 2020: Future Emerging Topics call
(FETOPEN), grant EU736876, project VISORSURF (http://www.visorsurf.eu
Realizing distance-selective interactions in a Rydberg-dressed atom array
Measurement-based quantum computing relies on the rapid creation of
large-scale entanglement in a register of stable qubits. Atomic arrays are well
suited to store quantum information, and entanglement can be created using
highly-excited Rydberg states. Typically, isolating pairs during gate operation
is difficult because Rydberg interactions feature long tails at large
distances. Here, we engineer distance-selective interactions that are strongly
peaked in distance through off-resonant laser coupling of molecular potentials
between Rydberg atom pairs. Employing quantum gas microscopy, we verify the
dressed interactions by observing correlated phase evolution using many-body
Ramsey interferometry. We identify atom loss and coupling to continuum modes as
a limitation of our present scheme and outline paths to mitigate these effects,
paving the way towards the creation of large-scale entanglement.Comment: 5 pages, 4 figures + supplementary informatio
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