652 research outputs found
Multiple membrane cavity optomechanics
We investigate theoretically the extension of cavity optomechanics to
multiple membrane systems. We describe such a system in terms of the coupling
of the collective normal modes of the membrane array to the light fields. We
show these modes can be optically addressed individually and be cooled, trapped
and characterized, e.g. via quantum nondemolition measurements. Analogies
between this system and a linear chain of trapped ions or dipolar molecules
imply the possibility of related applications in the quantum regime.Comment: 4 pages, 2 figure
Unitary transformation approach for the trapped ion dynamics
We present a way of treating the problem of the interaction of a single
trapped ion with laser beams based on successive aplications of unitary
transformations onto the Hamiltonian. This allows the diagonalization of the
Hamiltonian, by means of recursive relations, without performing the Lamb-Dicke
approximation.Comment: 8 page
Observation of the 1S0 - 3P0 clock transition in 27Al+
We report for the first time, laser spectroscopy of the 1S0 - 3P0 clock
transition in 27Al+. A single aluminum ion and a single beryllium ion are
simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb
repulsion. This coupling allows the beryllium ion to sympathetically cool the
aluminum ion, and also enables transfer of the aluminum's electronic state to
the beryllium's hyperfine state, which can be measured with high fidelity.
These techniques are applied to a measurement of the clock transition
frequency, \nu = 1 121 015 393 207 851(8) Hz. They are also used to measure the
lifetime of the metastable clock state, \tau = 20.6 +/- 1.4 s, the ground state
1S0 g-factor, g_S = -0.00079248(14), and the excited state 3P0 g-factor, g_P =
-0.00197686(21), in units of the Bohr magneton.Comment: 4 pages, 2 figures; updated author lis
Creating maximally entangled atomic states in a Bose-Einstein condensate
We propose a protocol to create maximally entangled pairs, triplets,
quartiles, and other clusters of Bose condensed atoms starting from a
condensate in the Mott insulator state. The essential element is to drive
single atom Raman transitions using laser pulses. Our scheme is simple,
efficient, and can be readily applied to the recent experimental system as
reported by Greiner {\it et al.} [ Nature {\bf 413}, 44 (2002)].Comment: 4 pages, 2 figures. revised version as to be publishe
Superfast Cooling
Currently laser cooling schemes are fundamentally based on the weak coupling
regime. This requirement sets the trap frequency as an upper bound to the
cooling rate. In this work we present a numerical study that shows the
feasibility of cooling in the strong coupling regime which then allows cooling
rates that are faster than the trap frequency with state of the art
experimental parameters. The scheme we present can work for trapped atoms or
ions as well as mechanical oscillators. It can also cool medium size ions
chains close to the ground state.Comment: 5 pages 4 figure
Cooling the Collective Motion of Trapped Ions to Initialize a Quantum Register
We report preparation in the ground state of collective modes of motion of
two trapped 9Be+ ions. This is a crucial step towards realizing quantum logic
gates which can entangle the ions' internal electronic states. We find that
heating of the modes of relative ion motion is substantially suppressed
relative to that of the center-of-mass modes, suggesting the importance of
these modes in future experiments.Comment: 5 pages, including 3 figures. RevTeX. PDF and PostScript available at
http://www.bldrdoc.gov/timefreq/ion/qucomp/papers.htm . final (published)
version. Eq. 1 and Table 1 slightly different from original submissio
Quantum state preparation and control of single molecular ions
Preparing molecules at rest and in a highly pure quantum state is a long
standing dream in chemistry and physics, so far achieved only for a select set
of molecules in dedicated experimental setups. Here, a quantum-limited
combination of mass spectrometry and Raman spectroscopy is proposed that should
be applicable to a wide range of molecular ions. Excitation of electrons in the
molecule followed by uncontrolled decay and branching into several lower energy
states is avoided. Instead, the molecule is always connected to rotational
states within the electronic and vibrational ground-state manifold, while a
co-trapped atomic ion provides efficient entropy removal and allows for
extraction of information on the molecule. The outlined techniques might enable
preparation, manipulation and measurement of a large multitude of molecular ion
species with the same instrument, with applications including, but not limited
to, precise determination of molecular properties and fundamental tests of
physics.Comment: 12 pages, 2 figures, reformatted for resubmissio
Decoherence of tripartite states - a trapped ion coupled to an optical cavity
We investigate the non-dissipative decoherence of three qubit system obtained
by manipulating the state of a trapped two-level ion coupled to an optical
cavity. Modelling the environment as a set of noninteracting harmonic
oscillators, analytical expressions for the state operator of tripartite
composite system, the probability of generating maximally entangled GHZ state,
and the population inversion have been obtained. The pointer observable is the
energy of the isolated quantum system. Coupling to environment results in
exponential decay of off diagonal matrix elements of the state operator with
time as well as a phase decoherence of the component states.
Numerical calculations to examine the time evolution of GHZ state generation
probability and population inversion for different system environment coupling
strengths are performed. Using negativity as an entanglement measure and linear
entropy as a measure of mixedness, the entanglement dynamics of the tripartite
system in the presence of decoherence is analysed.Comment: Revised version, errors corrected and references added. 12 pages, 6
figures, Presented at ICSSUR May 2005, Besancon, Franc
Randomized Benchmarking of Quantum Gates
A key requirement for scalable quantum computing is that elementary quantum
gates can be implemented with sufficiently low error. One method for
determining the error behavior of a gate implementation is to perform process
tomography. However, standard process tomography is limited by errors in state
preparation, measurement and one-qubit gates. It suffers from inefficient
scaling with number of qubits and does not detect adverse error-compounding
when gates are composed in long sequences. An additional problem is due to the
fact that desirable error probabilities for scalable quantum computing are of
the order of 0.0001 or lower. Experimentally proving such low errors is
challenging. We describe a randomized benchmarking method that yields estimates
of the computationally relevant errors without relying on accurate state
preparation and measurement. Since it involves long sequences of randomly
chosen gates, it also verifies that error behavior is stable when used in long
computations. We implemented randomized benchmarking on trapped atomic ion
qubits, establishing a one-qubit error probability per randomized pi/2 pulse of
0.00482(17) in a particular experiment. We expect this error probability to be
readily improved with straightforward technical modifications.Comment: 13 page
Single-qubit rotations in two-dimensional optical lattices with multiqubit addressing
Published versio
- …