24 research outputs found
Improved bounds on Lorentz violation from composite-pulse Ramsey spectroscopy in a trapped ion
In attempts to unify the four known fundamental forces in a single
quantum-consistent theory, it is suggested that Lorentz symmetry may be broken
at the Planck scale. Here we search for Lorentz violation at the low-energy
limit by comparing orthogonally oriented atomic orbitals in a
Michelson-Morley-type experiment. We apply a robust radiofrequency composite
pulse sequence in the manifold of an Yb ion, extending the
coherence time from 200 s to more than 1 s. In this manner, we fully
exploit the high intrinsic susceptibility of the state and take
advantage of its exceptionally long lifetime. We match the stability of the
previous best Lorentz symmetry test nearly an order of magnitude faster and
improve the constraints on the symmetry breaking coefficients to the 10
level. These results represent the most stringent test of this type of Lorentz
violation. The demonstrated method can be further extended to ion Coulomb
crystals
Towards a transportable aluminium ion quantum logic optical clock
With the advent of optical clocks featuring fractional frequency uncertainties on the order of 10-17 and below, new applications such as chronometric leveling with few-centimeter height resolution emerge. We are developing a transportable optical clock based on a single trapped aluminum ion, which is interrogated via quantum logic spectroscopy. We employ singly charged calcium as the logic ion for sympathetic cooling, state preparation, and readout. Here, we present a simple and compact physics and laser package for manipulation of 40Ca+. Important features are a segmented multilayer trap with separate loading and probing zones, a compact titanium vacuum chamber, a near-diffraction-limited imaging system with high numerical aperture based on a single biaspheric lens, and an all-in-fiber 40Ca+ repump laser system. We present preliminary estimates of the trap-induced frequency shifts on 27Al+, derived from measurements with a single calcium ion. The micromotion-induced second-order Doppler shift for 27Al+ has been determined to be δνEMMν=-0.4-0.3 +0.4Ă10-18 and the black-body radiation shift is δνBBR/ν = (-4.0 Âą 0.4) Ă 10-18. Moreover, heating rates of 30 (7) quanta per second at trap frequencies of Ďrad,Ca+ â 2Ď Ă 2.5 MHz (Ďax,Ca+ â 2Ď Ă 1.5 MHz) in radial (axial) direction have been measured, enabling interrogation times of a few hundreds of milliseconds
Sideband thermometry of ion crystals
Coulomb crystals of cold trapped ions are a leading platform for the
realisation of quantum processors and quantum simulations and, in quantum
metrology, for the construction of optical atomic clocks and for fundamental
tests of the Standard Model. For these applications, it is not only essential
to cool the ion crystal in all its degrees of freedom down to the quantum
ground state, but also to be able to determine its temperature with a high
accuracy. However, when a large ground-state cooled crystal is interrogated for
thermometry, complex many-body interactions take place, making it challenging
to accurately estimate the temperature with established techniques. In this
work we present a new thermometry method tailored for ion crystals. The method
is applicable to all normal modes of motion and does not suffer from a
computational bottleneck when applied to large ion crystals. We test the
temperature estimate with two experiments, namely with a 1D linear chain of 4
ions and a 2D crystal of 19 ions and verify the results, where possible, using
other methods. The results show that the new method is an accurate and
efficient tool for thermometry of ion crystals.Comment: 12+5 pages, 9+2 figures, Fig.3(b) was correcte
A high-precision rf trap with minimized micromotion for an In+ multiple-ion clock
We present an experiment to characterize our new linear ion trap designed for
the operation of a many-ion optical clock using 115-In^+ as clock ions. For the
characterization of the trap as well as the sympathetic cooling of the clock
ions we use 172-Yb^+. The trap design has been derived from finite element
method (FEM) calculations and a first prototype based on glass-reinforced
thermoset laminates was built. This paper details on the trap manufacturing
process and micromotion measurement. Excess micromotion is measured using
photon-correlation spectroscopy with a resolution of 1.1nm in motional
amplitude, and residual axial rf fields in this trap are compared to FEM
calculations. With this method, we demonstrate a sensitivity to systematic
clock shifts due to excess micromotion of |({\Delta}{\nu}/{\nu})| = 8.5x10^-20.
Based on the measurement of axial rf fields of our trap, we estimate a number
of twelve ions that can be stored per trapping segment and used as an optical
frequency standard with a fractional inaccuracy of \leq 1x10^-18 due to
micromotion.Comment: 19 pages with 14 picture