25 research outputs found
Spectroscopy On Aluminum Monochloride (alcl) For Laser Cooling And Trapping
Cooling atoms to the ultracold regime has allowed for studies of physics, ranging from many-body physics of quantum degenerate gases, quantum computing, precision measurements and tests of fundamental symmetries. Extending these experiments to polar molecules has the prospect of enhancing the sensitivity of such tests and of enabling novel studies, such as cold controlled chemistry. However, applying traditional laser cooling techniques to molecules is rendered difficult due their additional degrees of freedom which result in a limited photon scattering budget. Here we study aluminum monochloride (AlCl) as a promising candidate for laser cooling and trapping. The cooling transition at 261 nm () has a theoretical Franck-Condon factor of 99.88\% which allows for scattering ~800 photons with a single laser before the molecule enters an excited vibrational state. We use a frequency-tripled (SHG + SFG) Titanium-Sapphire laser and generate AlCl via laser ablation in a cryogenic helium buffer gas beam source. We will present our spectroscopy results on AlCl and the measured molecular constants of the state and compare them with ab-initio calculations. We will also discuss our estimates on the Franck-Condon factors
Algebraic synthesis of time-optimal unitaries in SU(2) with alternating controls
We present an algebraic framework to study the time-optimal synthesis of
arbitrary unitaries in SU(2), when the control set is restricted to rotations
around two non-parallel axes in the Bloch sphere. Our method bypasses commonly
used control-theoretical techniques, and easily imposes necessary conditions on
time-optimal sequences. In a straightforward fashion, we prove that
time-optimal sequences are solely parametrized by three rotation angles and
derive general bounds on those angles as a function of the relative rotation
speed of each control and the angle between the axes. Results are substantially
different whether both clockwise and counterclockwise rotations about the given
axes are allowed, or only clockwise rotations. In the first case, we prove that
any finite time-optimal sequence is composed at most of five control
concatenations, while for the more restrictive case, we present scaling laws on
the maximum length of any finite time-optimal sequence. The bounds we find for
both cases are stricter than previously published ones and severely constrain
the structure of time-optimal sequences, allowing for an efficient numerical
search of the time-optimal solution. Our results can be used to find the
time-optimal evolution of qubit systems under the action of the considered
control set, and thus potentially increase the number of realizable unitaries
before decoherence
Engineering vibrationally-assisted energy transfer in a trapped-ion quantum simulator
Many important chemical and biochemical processes in the condensed phase are
notoriously difficult to simulate numerically. Often this difficulty arises
from the complexity of simulating dynamics resulting from coupling to
structured, mesoscopic baths, for which no separation of time scales exists and
statistical treatments fail. A prime example of such a process is vibrationally
assisted charge or energy transfer. A quantum simulator, capable of
implementing a realistic model of the system of interest, could provide insight
into these processes in regimes where numerical treatments fail. We take a
first step towards modeling such transfer processes using an ion trap quantum
simulator. By implementing a minimal model, we observe vibrationally assisted
energy transport between the electronic states of a donor and an acceptor ion
augmented by coupling the donor ion to its vibration. We tune our simulator
into several parameter regimes and, in particular, investigate the transfer
dynamics in the nonperturbative regime often found in biochemical situations
Radio Frequency Magneto-Optical Trapping of CaF with High Density
We demonstrate significantly improved magneto-optical trapping of molecules
using a very slow cryogenic beam source and RF modulated and DC magnetic
fields. The RF MOT confines CaF molecules at a density of
cm, which is an order of magnitude greater than
previous molecular MOTs. Near Doppler-limited temperatures of K
are attained. The achieved density enables future work to directly load optical
tweezers and create optical arrays for quantum simulation.Comment: 5 Pages, 4 Figure
One dimensional magneto-optical compression of a cold CaF molecular beam
We demonstrate with a RF-MOT the one dimensional, transverse magneto-optical
compression of a cold beam of calcium monofluoride (CaF). By continually
alternating the magnetic field direction and laser polarizations of the
magneto-optical trap, a photon scattering rate of 0.4 MHz is
achieved. A 3D model for this RF-MOT, validated by agreement with data,
predicts a 3D RF-MOT capture velocity for CaF of 5 m/s
Achieving translational symmetry in trapped cold ion rings
Spontaneous symmetry breaking is a universal concept throughout science. For
instance, the Landau-Ginzburg paradigm of translational symmetry breaking
underlies the classification of nearly all quantum phases of matter and
explains the emergence of crystals, insulators, and superconductors. Usually,
the consequences of translational invariance are studied in large systems to
suppress edge effects which cause undesired symmetry breaking. While this
approach works for investigating global properties, studies of local
observables and their correlations require access and control of the individual
constituents. Periodic boundary conditions, on the other hand, could allow for
translational symmetry in small systems where single particle control is
achievable. Here, we crystallize up to fifteen 40Ca+ ions in a microscopic ring
with inherent periodic boundary conditions. We show the ring's translational
symmetry is preserved at millikelvin temperatures by delocalizing the Doppler
laser cooled ions. This establishes an upper bound for undesired symmetry
breaking at a level where quantum control becomes feasible. These findings pave
the way towards studying quantum many-body physics with translational symmetry
at the single particle level in a variety of disciplines from simulation of
Hawking radiation to exploration of quantum phase transitions.Comment: 15 pages, 4 figure
Laser slowing of CaF molecules to near the capture velocity of a molecular MOT
Laser slowing of CaF molecules down to the capture velocity of a
magneto-optical trap (MOT) for molecules is achieved. Starting from a two-stage
buffer gas beam source, we apply frequency-broadened "white-light" slowing and
observe approximately 6x10^4 CaF molecules with velocities near 10\,m/s. CaF is
a candidate for collisional studies in the mK regime. This work represents a
significant step towards magneto-optical trapping of CaF