528 research outputs found
Resonant coupling of a Bose-Einstein condensate to a micromechanical oscillator
We report experiments in which the vibrations of a micromechanical oscillator
are coupled to the motion of Bose-condensed atoms in a trap. The interaction
relies on surface forces experienced by the atoms at about one micrometer
distance from the mechanical structure. We observe resonant coupling to several
well-resolved mechanical modes of the condensate. Coupling via surface forces
does not require magnets, electrodes, or mirrors on the oscillator and could
thus be employed to couple atoms to molecular-scale oscillators such as carbon
nanotubes.Comment: 9 pages, 4 figure
Atom chip based generation of entanglement for quantum metrology
Atom chips provide a versatile `quantum laboratory on a microchip' for
experiments with ultracold atomic gases. They have been used in experiments on
diverse topics such as low-dimensional quantum gases, cavity quantum
electrodynamics, atom-surface interactions, and chip-based atomic clocks and
interferometers. A severe limitation of atom chips, however, is that techniques
to control atomic interactions and to generate entanglement have not been
experimentally available so far. Such techniques enable chip-based studies of
entangled many-body systems and are a key prerequisite for atom chip
applications in quantum simulations, quantum information processing, and
quantum metrology. Here we report experiments where we generate multi-particle
entanglement on an atom chip by controlling elastic collisional interactions
with a state-dependent potential. We employ this technique to generate
spin-squeezed states of a two-component Bose-Einstein condensate and show that
they are useful for quantum metrology. The observed 3.7 dB reduction in spin
noise combined with the spin coherence imply four-partite entanglement between
the condensate atoms and could be used to improve an interferometric
measurement by 2.5 dB over the standard quantum limit. Our data show good
agreement with a dynamical multi-mode simulation and allow us to reconstruct
the Wigner function of the spin-squeezed condensate. The techniques
demonstrated here could be directly applied in chip-based atomic clocks which
are currently being set up
An optical lattice on an atom chip
Optical dipole traps and atom chips are two very powerful tools for the
quantum manipulation of neutral atoms. We demonstrate that both methods can be
combined by creating an optical lattice potential on an atom chip. A
red-detuned laser beam is retro-reflected using the atom chip surface as a
high-quality mirror, generating a vertical array of purely optical oblate
traps. We load thermal atoms from the chip into the lattice and observe cooling
into the two-dimensional regime where the thermal energy is smaller than a
quantum of transverse excitation. Using a chip-generated Bose-Einstein
condensate, we demonstrate coherent Bloch oscillations in the lattice.Comment: 3 pages, 2 figure
Quantum computing implementations with neutral particles
We review quantum information processing with cold neutral particles, that
is, atoms or polar molecules. First, we analyze the best suited degrees of
freedom of these particles for storing quantum information, and then we discuss
both single- and two-qubit gate implementations. We focus our discussion mainly
on collisional quantum gates, which are best suited for atom-chip-like devices,
as well as on gate proposals conceived for optical lattices. Additionally, we
analyze schemes both for cold atoms confined in optical cavities and hybrid
approaches to entanglement generation, and we show how optimal control theory
might be a powerful tool to enhance the speed up of the gate operations as well
as to achieve high fidelities required for fault tolerant quantum computation.Comment: 19 pages, 12 figures; From the issue entitled "Special Issue on
Neutral Particles
Inferring and perturbing cell fate regulomes in human brain organoids
Self-organizing neural organoids grown from pluripotent stem cells(1-3) combined with single-cell genomic technologies provide opportunities to examine gene regulatory networks underlying human brain development. Here we acquire single-cell transcriptome and accessible chromatin data over a dense time course in human organoids covering neuroepithelial formation, patterning, brain regionalization and neurogenesis, and identify temporally dynamic and brain-region-specific regulatory regions. We developed Pando-a flexible framework that incorporates multi-omic data and predictions of transcription-factor-binding sites to infer a global gene regulatory network describing organoid development. We use pooled genetic perturbation with single-cell transcriptome readout to assess transcription factor requirement for cell fate and state regulation in organoids. We find that certain factors regulate the abundance of cell fates, whereas other factors affect neuronal cell states after differentiation. We show that the transcription factor GLI3 is required for cortical fate establishment in humans, recapitulating previous research performed in mammalian model systems. We measure transcriptome and chromatin accessibility in normal or GLI3-perturbed cells and identify two distinct GLI3 regulomes that are central to telencephalic fate decisions: one regulating dorsoventral patterning with HES4/5 as direct GLI3 targets, and one controlling ganglionic eminence diversification later in development. Together, we provide a framework for how human model systems and single-cell technologies can be leveraged to reconstruct human developmental biology
Coupling ultracold atoms to mechanical oscillators
In this article we discuss and compare different ways to engineer an
interface between ultracold atoms and micro- and nanomechanical oscillators. We
start by analyzing a direct mechanical coupling of a single atom or ion to a
mechanical oscillator and show that the very different masses of the two
systems place a limit on the achievable coupling constant in this scheme. We
then discuss several promising strategies for enhancing the coupling:
collective enhancement by using a large number of atoms in an optical lattice
in free space, coupling schemes based on high-finesse optical cavities, and
coupling to atomic internal states. Throughout the manuscript we discuss both
theoretical proposals and first experimental implementations.Comment: 19 pages, 9 figure
Characterization of RNA content in individual phase-separated coacervate microdroplets
Condensates formed by complex coacervation are hypothesized to have played a crucial part during the origin-of-life. In living cells, condensation organizes biomolecules into a wide range of membraneless compartments. Although RNA is a key component of biological condensates and the central component of the RNA world hypothesis, little is known about what determines RNA accumulation in condensates and to which extend single condensates differ in their RNA composition. To address this, we developed an approach to read the RNA content from single synthetic and protein-based condensates using high-throughput sequencing. We find that certain RNAs efficiently accumulate in condensates. These RNAs are strongly enriched in sequence motifs which show high sequence similarity to short interspersed elements (SINEs). We observe similar results for protein-derived condensates, demonstrating applicability across different in vitro reconstituted membraneless organelles. Thus, our results provide a new inroad to explore the RNA content of phase-separated droplets at single condensate resolution
Inductively guided circuits for ultracold dressed atoms
Recent progress in optics, atomic physics and material science has paved the way to study quantum effects in ultracold atomic alkali gases confined to non-trivial geometries. Multiply connected traps for cold atoms can be prepared by combining inhomogeneous distributions of DC and radio-frequency electromagnetic fields with optical fields that require complex systems for frequency control and stabilization. Here we propose a flexible and robust scheme that creates closed quasi-one-dimensional guides for ultracold atoms through the ‘dressing’ of hyperfine sublevels of the atomic ground state, where the dressing field is spatially modulated by inductive effects over a micro-engineered conducting loop. Remarkably, for commonly used atomic species (for example, 7Li and 87Rb), the guide operation relies entirely on controlling static and low-frequency fields in the regimes of radio-frequency and microwave frequencies. This novel trapping scheme can be implemented with current technology for micro-fabrication and electronic control
Scalable Neutral Atom Quantum Computer with Interaction on Demand: Proposal for Selective Application of Two-Qubit Gate
We propose a scalable neutral atom quantum computer with an on-demand
interaction through a selective two-qubit gate operation. Atoms are trapped by
a lattice of near field Fresnel diffraction lights so that each trap captures a
single atom. One-qubit gate operation is implemented by a gate control laser
beam which is applied to an individual atom. Two-qubit gate operation between
an arbitrary pair of atoms is implemented by sending these atoms to a
state-dependent optical lattice and making them collide so that a particular
two-qubit state acquires a dynamical phase. We give numerical evaluations
corresponding to these processes, from which we estimate the upper bound of a
two-qubit gate operation time and corresponding gate fidelity. Our proposal is
feasible within currently available technology developed in cold atom gas,
MEMS, nanolithography, and various areas in optics.Comment: 10 pages, 9 figur
Matter-wave interferometry in a double well on an atom chip
Matter-wave interference experiments enable us to study matter at its most
basic, quantum level and form the basis of high-precision sensors for
applications such as inertial and gravitational field sensing. Success in both
of these pursuits requires the development of atom-optical elements that can
manipulate matter waves at the same time as preserving their coherence and
phase. Here, we present an integrated interferometer based on a simple,
coherent matter-wave beam splitter constructed on an atom chip. Through the use
of radio-frequency-induced adiabatic double-well potentials, we demonstrate the
splitting of Bose-Einstein condensates into two clouds separated by distances
ranging from 3 to 80 microns, enabling access to both tunnelling and isolated
regimes. Moreover, by analysing the interference patterns formed by combining
two clouds of ultracold atoms originating from a single condensate, we measure
the deterministic phase evolution throughout the splitting process. We show
that we can control the relative phase between the two fully separated samples
and that our beam splitter is phase-preserving
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