2,273 research outputs found
A trapped single ion inside a Bose-Einstein condensate
Improved control of the motional and internal quantum states of ultracold
neutral atoms and ions has opened intriguing possibilities for quantum
simulation and quantum computation. Many-body effects have been explored with
hundreds of thousands of quantum-degenerate neutral atoms and coherent
light-matter interfaces have been built. Systems of single or a few trapped
ions have been used to demonstrate universal quantum computing algorithms and
to detect variations of fundamental constants in precision atomic clocks. Until
now, atomic quantum gases and single trapped ions have been treated separately
in experiments. Here we investigate whether they can be advantageously combined
into one hybrid system, by exploring the immersion of a single trapped ion into
a Bose-Einstein condensate of neutral atoms. We demonstrate independent control
over the two components within the hybrid system, study the fundamental
interaction processes and observe sympathetic cooling of the single ion by the
condensate. Our experiment calls for further research into the possibility of
using this technique for the continuous cooling of quantum computers. We also
anticipate that it will lead to explorations of entanglement in hybrid quantum
systems and to fundamental studies of the decoherence of a single, locally
controlled impurity particle coupled to a quantum environment
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A Trapped Single Ion Inside a Bose-Einstein Condensate
In recent years, improved control of the motional and internal quantum states of ultracold neutral atoms and ions has opened intriguing possibilities for quantum simulation and quantum computation. Many-body effects have been explored with hundreds of thousands of quantum-degenerate neutral atoms and coherent light-matter interfaces have been built. Systems of single or a few trapped ions have been used to demonstrate universal quantum computing algorithms and to detect variations of fundamental constants in precision atomic clocks. Now in our experiment we investigate how the two systems can be advantageously combined. We immerse a single trapped Yb+ ion in a Bose-Einstein condensate of Rb atoms. Our hybrid setup consists of a linear RF-Paul trap which is overlapped with a magnetic trap and an optical dipole trap for the neutral atoms.
A first synergetic effect is the sympathetic cooling of the trapped ions to very low temperatures through collisions with the ultracold neutral gas and thus without applying laser light to the ions. We observe the dynamics of this effect by measuring the mean ion energy after having an initially hot ion immersed into the condensate for various interaction times, while at the same time monitoring the effects of the collisions on the condensate. The observed ion cooling effect calls for further research into the possibility of using such hybrid systems for the continuous cooling of quantum computers.
To this end a good understanding of the fundamental interaction processes between the ion and the neutrals is essential. We investigate the energy dependent elastic scattering properties by measuring neutral atom losses and temperature increase from an ultracold thermal cloud of Rb. By comparison with a Monte-Carlo simulation we gain a deeper understanding of how the different parameters affect the collisional effects. Additionally, we observe charge exchange reactions at the single particle level and measure the energy-independent reaction rate constants. The reaction products are identified by in-trap mass spectrometry, revealing the branching ratio between radiative and non-radiative charge exchange processes
Quantum metrology with nonclassical states of atomic ensembles
Quantum technologies exploit entanglement to revolutionize computing,
measurements, and communications. This has stimulated the research in different
areas of physics to engineer and manipulate fragile many-particle entangled
states. Progress has been particularly rapid for atoms. Thanks to the large and
tunable nonlinearities and the well developed techniques for trapping,
controlling and counting, many groundbreaking experiments have demonstrated the
generation of entangled states of trapped ions, cold and ultracold gases of
neutral atoms. Moreover, atoms can couple strongly to external forces and light
fields, which makes them ideal for ultra-precise sensing and time keeping. All
these factors call for generating non-classical atomic states designed for
phase estimation in atomic clocks and atom interferometers, exploiting
many-body entanglement to increase the sensitivity of precision measurements.
The goal of this article is to review and illustrate the theory and the
experiments with atomic ensembles that have demonstrated many-particle
entanglement and quantum-enhanced metrology.Comment: 76 pages, 40 figures, 1 table, 603 references. Some figures bitmapped
at 300 dpi to reduce file siz
Hybrid quantum systems of atoms and ions
In recent years, ultracold atoms have emerged as an exceptionally
controllable experimental system to investigate fundamental physics, ranging
from quantum information science to simulations of condensed matter models.
Here we go one step further and explore how cold atoms can be combined with
other quantum systems to create new quantum hybrids with tailored properties.
Coupling atomic quantum many-body states to an independently controllable
single-particle gives access to a wealth of novel physics and to completely new
detection and manipulation techniques. We report on recent experiments in which
we have for the first time deterministically placed a single ion into an atomic
Bose Einstein condensate. A trapped ion, which currently constitutes the most
pristine single particle quantum system, can be observed and manipulated at the
single particle level. In this single-particle/many-body composite quantum
system we show sympathetic cooling of the ion and observe chemical reactions of
single particles in situ.Comment: ICAP proceeding
Dynamics of a cold trapped ion in a Bose-Einstein condensate
We investigate the interaction of a laser-cooled trapped ion (Ba or
Rb) with an optically confined Rb Bose-Einstein condensate (BEC).
The system features interesting dynamics of the ion and the atom cloud as
determined by their collisions and their motion in their respective traps.
Elastic as well as inelastic processes are observed and their respective cross
sections are determined. We demonstrate that a single ion can be used to probe
the density profile of an ultracold atom cloud.Comment: 4 pages, 5 figure
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
Coupling a single electron to a Bose-Einstein condensate
The coupling of electrons to matter is at the heart of our understanding of
material properties such as electrical conductivity. One of the most intriguing
effects is that electron-phonon coupling can lead to the formation of a Cooper
pair out of two repelling electrons, the basis for BCS superconductivity. Here
we study the interaction of a single localized electron with a Bose-Einstein
condensate (BEC) and show that it can excite phonons and eventually set the
whole condensate into a collective oscillation. We find that the coupling is
surprisingly strong as compared to ionic impurities due to the more favorable
mass ratio. The electron is held in place by a single charged ionic core
forming a Rydberg bound state. This Rydberg electron is described by a
wavefunction extending to a size comparable to the dimensions of the BEC,
namely up to 8 micrometers. In such a state, corresponding to a principal
quantum number of n=202, the Rydberg electron is interacting with several tens
of thousands of condensed atoms contained within its orbit. We observe
surprisingly long lifetimes and finite size effects due to the electron
exploring the wings of the BEC. Based on our results we anticipate future
experiments on electron wavefunction imaging, investigation of phonon mediated
coupling of single electrons, and applications in quantum optics.Comment: 4 pages, 3 figures and supplementary informatio
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