24 research outputs found
Heteronuclear molecules in an optical lattice: Theory and experiment
We study properties of two different atoms at a single optical lattice site
at a heteronuclear atomic Feshbach resonance. We calculate the energy spectrum,
the efficiency of rf association and the lifetime as a function of magnetic
field and compare the results with the experimental data obtained for K-40 and
Rb-87 [C. Ospelkaus et al., Phys. Rev. Lett. 97, 120402 (2006)]. We treat the
interaction in terms of a regularized delta function pseudopotential and
consider the general case of particles with different trap frequencies, where
the usual approach of separating center-of-mass and relative motion fails. We
develop an exact diagonalization approach to the coupling between
center-of-mass and relative motion and numerically determine the spectrum of
the system. At the same time, our approach allows us to treat the anharmonicity
of the lattice potential exactly. Within the pseudopotential model, the center
of the Feshbach resonance can be precisely determined from the experimental
data.Comment: 9 pages, 7 figures, revised discussion of transfer efficienc
Elementary laser-less quantum logic operations with (anti-)protons in Penning traps
Static magnetic field gradients superimposed on the electromagnetic trapping
potential of a Penning trap can be used to implement laser-less spin-motion
couplings that allow the realization of elementary quantum logic operations in
the radio-frequency regime. An important scenario of practical interest is the
application to -factor measurements with single (anti-)protons to test the
fundamental charge, parity, time reversal (CPT) invariance as pursued in the
BASE collaboration [Smorra et al., Eur. Phys. J. Spec. Top. 224, 3055-3108
(2015), Smorra et al., Nature 550, 371-374 (2017), Schneider et al., Science
358, 1081-1084 (2017)]. We discuss the classical and quantum behavior of a
charged particle in a Penning trap with a superimposed magnetic field gradient.
Using analytic and numerical calculations, we find that it is possible to carry
out a SWAP gate between the spin and the motional qubit of a single
(anti-)proton with high fidelity, provided the particle has been initialized in
the motional ground state. We discuss the implications of our findings for the
realization of quantum logic spectroscopy in this system.Comment: 10 pages, 4 figures, 1 table; published versio
Initialization of quantum simulators by sympathetic cooling
Simulating computationally intractable many-body problems on a quantum simulator holds great potential to deliver insights into physical, chemical, and biological systems. While the implementation of Hamiltonian dynamics within a quantum simulator has already been demonstrated in many experiments, the problem of initialization of quantum simulators to a suitable quantum state has hitherto remained mostly unsolved. Here, we show that already a single dissipatively driven auxiliary particle can efficiently prepare the quantum simulator in a low-energy state of largely arbitrary Hamiltonians. We demonstrate the scalability of our approach and show that it is robust against unwanted sources of decoherence. While our initialization protocol is largely independent of the physical realization of the simulation device, we provide an implementation example for a trapped ion quantum simulator
Optical stimulated-Raman sideband spectroscopy of a single 9Be+ ion in a Penning trap
We demonstrate optical sideband spectroscopy of a single 9Be+ ion in a cryogenic 5 tesla Penning trap using two-photon stimulated-Raman transitions between the two Zeeman sublevels of the 1s22s ground state manifold. By applying two complementary coupling schemes, we accurately measure Raman resonances with and without contributions from motional sidebands. From the latter we obtain an axial sideband spectrum with an effective mode temperature of (3.1±0.4) mK. These results are a key step for quantum logic operations in Penning traps, applicable to high-precision matter-antimatter comparison tests in the baryonic sector of the standard model
Resolved-sideband cooling of a single Be ion in a Penning trap
Manipulating individual trapped ions at the single quantum level has become
standard practice in radio-frequency ion traps, enabling applications from
quantum information processing to precision metrology. The key ingredient is
ground-state cooling of the particle's motion through resolved-sideband laser
cooling. Ultra-high-presicion experiments using Penning ion traps will greatly
benefit from the reduction of systematic errors offered by full motional
control, with applications to atomic masses and -factor measurements,
determinations of fundamental constants or related tests of fundamental
physics. In addition, it will allow to implement quantum logic spectroscopy, a
technique that has enabled a new class of precision measurements in
radio-frequency ion traps. Here we demonstrate resolved-sideband laser cooling
of the axial motion of a single Be ion in a cryogenic 5 Tesla Penning
trap system using a two-photon stimulated-Raman process, reaching a mean phonon
number of . This is a fundamental step in the
implementation of quantum logic spectroscopy for matter-antimatter comparison
tests in the baryonic sector of the Standard Model and a key step towards
improved precision experiments in Penning traps operating at the quantum limit.Comment: 6 pages, 5 figure
Unit cell of a Penning micro-trap quantum processor
Trapped ions in radio-frequency traps are among the leading approaches for
realizing quantum computers, due to high-fidelity quantum gates and long
coherence times. However, the use of radio-frequencies presents a number of
challenges to scaling, including requiring compatibility of chips with high
voltages, managing power dissipation and restricting transport and placement of
ions. By replacing the radio-frequency field with a 3 T magnetic field, we here
realize a micro-fabricated Penning ion trap which removes these restrictions.
We demonstrate full quantum control of an ion in this setting, as well as the
ability to transport the ion arbitrarily in the trapping plane above the chip.
This unique feature of the Penning micro-trap approach opens up a modification
of the Quantum CCD architecture with improved connectivity and flexibility,
facilitating the realization of large-scale trapped-ion quantum computing,
quantum simulation and quantum sensing
Quantum logic inspired techniques for spacetime-symmetry tests with (anti-)protons
Cosmological observations as well as theoretical approaches to physics beyond the standard model provide strong motivations for experimental tests of fundamental symmetries, such as CPT invariance. In this context, the availability of cold baryonic antimatter at CERN has opened an avenue for ultrahigh-precision comparisons of protons and antiprotons in Penning traps. This work discusses an experimental method inspired by quantum logic techniques that will improve particle localization and readout speed in such experiments. The method allows for sympathetic cooling of the (anti-)proton to its quantum-mechanical ground state as well as the readout of its spin alignment, replacing the commonly used continuous Stern–Gerlach effect. Both of these features are achieved through coupling to a laser-cooled 'logic' ion co-trapped in a double-well potential. This technique will boost the measurement sampling rate and will thus provide results with lower statistical uncertainty, contributing to stringent searches for time dependent variations in the data. Such measurements ultimately yield extremely high sensitivities to CPT violating coefficients acting on baryons in the standard-model extension, will allow the exploration of previously unmeasured types of symmetry violations, and will enable antimatter-based axion-like dark matter searches with improved mass resolution
Formation of Two-Ion Crystals by Injection from a Paul-Trap Source into a High-Magnetic-Field Penning Trap
Two-ion crystals constitute a platform for investigations of quantum nature
that can be extended to any ion species or charged particle provided one of the
ions in the crystal can be directly laser-cooled and manipulated with laser
radiation. This paper presents the formation of two-ion crystals for quantum
metrology in a 7-tesla open-ring Penning trap. Ca ions are produced
either internally by photoionization or externally in a (Paul-trap) source,
transported through the strong magnetic field gradient of the superconducting
solenoid, and captured in-flight with a mean kinetic energy of a few
electronvolts with respect to the minimum of the Penning-trap potential well.
Laser cooling of the two-ion crystal in a strong magnetic field towards
reaching the quantum regime is also presented with particular emphasis on the
cooling of the radial modes