41 research outputs found
Programmable N-body interactions with trapped ions
Trapped atomic ion qubits or effective spins are a powerful quantum platform
for quantum computation and simulation, featuring densely connected and
efficiently programmable interactions between the spins. While native
interactions between trapped ion spins are typically pairwise, many quantum
algorithms and quantum spin models naturally feature couplings between
triplets, quartets or higher orders of spins. Here we formulate and analyze a
mechanism that extends the standard M\o{}lmer-S\o{}rensen pairwise entangling
gate and generates a controllable and programmable coupling between spins
of trapped ions. We show that spin-dependent optical forces applied at twice
the motional frequency generate a coordinate-transformation of the collective
ion motion in phase-space, rendering displacement forces that are nonlinear in
the spin operators. We formulate a simple framework that enables a systematic
and faithful construction of high-order spin Hamiltonians and gates, including
the effect of multiple modes of motion, and characterize the performance of
such operations under realistic conditions
Micromotion-induced Limit to Atom-Ion Sympathetic Cooling in Paul Traps
We present and derive analytic expressions for a fundamental limit to the
sympathetic cooling of ions in radio-frequency traps using cold atoms. The
limit arises from the work done by the trap electric field during a long-range
ion-atom collision and applies even to cooling by a zero-temperature atomic gas
in a perfectly compensated trap. We conclude that in current experimental
implementations this collisional heating prevents access to the regimes of
single-partial-wave atom-ion interaction or quantized ion motion. We determine
conditions on the atom-ion mass ratio and on the trap parameters for reaching
the s-wave collision regime and the trap ground state
Observation of a Strong Atom-Dimer Attraction in a Mass-Imbalanced Fermi-Fermi Mixture
We investigate a mixture of ultracold fermionic K atoms and weakly
bound LiK dimers on the repulsive side of a heteronuclear atomic
Feshbach resonance. By radio-frequency spectroscopy we demonstrate that the
normally repulsive atom-dimer interaction is turned into a strong attraction.
The phenomenon can be understood as a three-body effect in which two heavy
K fermions exchange the light Li atom, leading to attraction in
odd partial-wave channels (mainly p-wave). Our observations show that mass
imbalance in a fermionic system can profoundly change the character of
interactions as compared to the well-established mass-balanced case
Demonstration of three- and four-body interactions between trapped-ion spins
Quantum processors use the native interactions between effective spins to
simulate Hamiltonians or execute quantum gates. In most processors, the native
interactions are pairwise, limiting the efficiency of controlling entanglement
between many qubits. Here we experimentally demonstrate a new class of native
interactions between trapped-ion qubits, extending conventional pairwise
interactions to higher order. We realize three- and four-body spin interactions
as examples, showing that high-order spin polynomials may serve as a new
toolbox for quantum information applications
Bright Source of Cold Ions for Surface-Electrode Traps
We produce large numbers of low-energy ions by photoionization of
laser-cooled atoms inside a surface-electrode-based Paul trap. The
isotope-selective trap loading rate of Yb ions/s exceeds
that attained by photoionization (electron impact ionization) of an atomic beam
by four (six) orders of magnitude. Traps as shallow as 0.13 eV are easily
loaded with this technique. The ions are confined in the same spatial region as
the laser-cooled atoms, which will allow the experimental investigation of
interactions between cold ions and cold atoms or Bose-Einstein condensates.Comment: Paper submitted to PRL for review on 2/1/0
Observation of Cold Collisions between Trapped Ions and Trapped Atoms
We demonstrate a double-trap system well suited to study cold collisions
between trapped ions and trapped atoms. Using Yb ions confined in a Paul
trap and Yb atoms in a magneto-optical trap, we investigate charge-exchange
collisions of several isotopes for collision energies down to 400 neV (5 mK).
The measured rate coefficient of cms, constant
over four orders of magnitude in collision energy, is in good agreement with
that derived from a semiclassical Langevin model for an atomic polarizability
of 143 a.u.Comment: 4 pages, 4 figures; Revision 1/V2: Revised in response to PRL
Referees' comment
One-dimensional array of ion chains coupled to an optical cavity
We present a novel hybrid system where an optical cavity is integrated with a
microfabricated planar-electrode ion trap. The trap electrodes produce a
tunable periodic potential allowing the trapping of up to 50 separate ion
chains spaced by 160 m along the cavity axis. Each chain can contain up to
20 individually addressable Yb\textsuperscript{+} ions coupled to the cavity
mode. We demonstrate deterministic distribution of ions between the sites of
the electrostatic periodic potential and control of the ion-cavity coupling.
The measured strength of this coupling should allow access to the strong
collective coupling regime with 10 ions. The optical cavity could
serve as a quantum information bus between ions or be used to generate a strong
wavelength-scale periodic optical potential.Comment: 15 pages, 6 figures, submitted to New Journal of Physic