188 research outputs found
Quantum Gates and Memory using Microwave Dressed States
Trapped atomic ions have been successfully used for demonstrating basic
elements of universal quantum information processing (QIP). Nevertheless,
scaling up of these methods and techniques to achieve large scale universal
QIP, or more specialized quantum simulations remains challenging. The use of
easily controllable and stable microwave sources instead of complex laser
systems on the other hand promises to remove obstacles to scalability.
Important remaining drawbacks in this approach are the use of magnetic field
sensitive states, which shorten coherence times considerably, and the
requirement to create large stable magnetic field gradients. Here, we present
theoretically a novel approach based on dressing magnetic field sensitive
states with microwave fields which addresses both issues and permits fast
quantum logic. We experimentally demonstrate basic building blocks of this
scheme to show that these dressed states are long-lived and coherence times are
increased by more than two orders of magnitude compared to bare magnetic field
sensitive states. This changes decisively the prospect of microwave-driven ion
trap QIP and offers a new route to extend coherence times for all systems that
suffer from magnetic noise such as neutral atoms, NV-centres, quantum dots, or
circuit-QED systems.Comment: 9 pages, 4 figure
Multi-qubit gate with trapped ions for microwave and laser-based implementation
A proposal for a phase gate and a Mølmer–Sørensen gate in the dressed state basis is presented. In order to perform the multi-qubit interaction, a strong magnetic field gradient is required to couple the phonon-bus to the qubit states. The gate is performed using resonant microwave driving fields together with either a radio-frequency (RF) driving field, or additional detuned microwave driving fields. The gate is robust to ambient magnetic field fluctuations due to an applied resonant microwave driving field. Furthermore, the gate is robust to fluctuations in the microwave Rabi frequency and is decoupled from phonon dephasing due to a resonant RF or a detuned microwave driving field. This makes this new gate an attractive candidate for the implementation of high-fidelity microwave based multi-qubit gates. The proposal can also be realized in laser-based set-ups
Quantum gates using electronic and nuclear spins of Yb in a magnetic field gradient
An efficient scheme is proposed to carry out gate operations on an array of
trapped Yb ions, based on a previous proposal using both electronic and
nuclear degrees of freedom in a magnetic field gradient. For this purpose we
consider the Paschen-Back regime (strong magnetic field) and employ a
high-field approximation in this treatment. We show the possibility to suppress
the unwanted coupling between the electron spins by appropriately swapping
states between electronic and nuclear spins. The feasibility of generating the
required high magnetic field is discussed
Franck-Condon Physics in A Single Trapped Ion
We propose how to explore the Franck-Condon (FC) physics via a single ion
confined in a spin-dependent potential, formed by the combination of a Paul
trap and a magnetic field gradient. The correlation between electronic and
vibrational degrees of freedom, called as electron-vibron coupling, is induced
by a nonzero gradient. For a sufficiently strong electron-vibron coupling, the
FC blockade of low-lying vibronic transitions takes place. We analyze the
feasibility of observing the FC physics in a single trapped ion, and
demonstrate various potential applications of the ionic FC physics in quantum
state engineering and quantum information processing.Comment: 7 pages, 5 figure
Simulation of Quantum Magnetism in Mixed Spin Systems with Impurity Doped Ion Crystal
We propose the realization of linear crystals of cold ions which contain
different atomic species for investigating quantum phase transitions and
frustration effects in spin system beyond the commonly discussed case of
. Mutual spin-spin interactions between ions can be tailored via the
Zeeman effect by applying oscillating magnetic fields with strong gradients.
Further, collective vibrational modes in the mixed ion crystal can be used to
enhance and to vary the strength of spin-spin interactions and even to switch
those forces from a ferro- to an antiferromagnetic character. We consider the
behavior of the effective spin-spin couplings in an ion crystal of spin-1/2
ions doped with high magnetic moment ions with spin S=3. We analyze the ground
state phase diagram and find regions with different spin orders including
ferrimagnetic states. In the most simple non-trivial example we deal with a
linear Ca, Mn, Ca crystal with spins of \{1/2,3,1/2}. To
show the feasibility with current state-of-the-art experiments, we discuss how
quantum phases might be detected using a collective Stern-Gerlach effect of the
ion crystal and high resolution spectroscopy. Here, the state-dependent
laser-induced fluorescence of the indicator spin-1/2 ion, of species
Ca, reveals also the spin state of the simulator spin-3 ions,
Mn as this does not possess suitable levels for optical excitation
and detection.Comment: 15 pages, 5 figure
A trapped-ion local field probe
We introduce a measurement scheme that utilizes a single ion as a local field
probe. The ion is confined in a segmented Paul trap and shuttled around to
reach different probing sites. By the use of a single atom probe, it becomes
possible characterizing fields with spatial resolution of a few nm within an
extensive region of millimeters. We demonstrate the scheme by accurately
investigating the electric fields providing the confinement for the ion. For
this we present all theoretical and practical methods necessary to generate
these potentials. We find sub-percent agreement between measured and calculated
electric field values
Complete devil's staircase and crystal--superfluid transitions in a dipolar XXZ spin chain: A trapped ion quantum simulation
Systems with long-range interactions show a variety of intriguing properties:
they typically accommodate many meta-stable states, they can give rise to
spontaneous formation of supersolids, and they can lead to counterintuitive
thermodynamic behavior. However, the increased complexity that comes with
long-range interactions strongly hinders theoretical studies. This makes a
quantum simulator for long-range models highly desirable. Here, we show that a
chain of trapped ions can be used to quantum simulate a one-dimensional model
of hard-core bosons with dipolar off-site interaction and tunneling, equivalent
to a dipolar XXZ spin-1/2 chain. We explore the rich phase diagram of this
model in detail, employing perturbative mean-field theory, exact
diagonalization, and quasiexact numerical techniques (density-matrix
renormalization group and infinite time evolving block decimation). We find
that the complete devil's staircase -- an infinite sequence of crystal states
existing at vanishing tunneling -- spreads to a succession of lobes similar to
the Mott-lobes found in Bose--Hubbard models. Investigating the melting of
these crystal states at increased tunneling, we do not find (contrary to
similar two-dimensional models) clear indications of supersolid behavior in the
region around the melting transition. However, we find that inside the
insulating lobes there are quasi-long range (algebraic) correlations, opposed
to models with nearest-neighbor tunneling which show exponential decay of
correlations
Thick-film technology for ultra high vacuum interfaces of micro-structured traps
We adopt thick-film technology to produce ultra high vacuum compatible
interfaces for electrical signals. These interfaces permit voltages of hundreds
of Volts and currents of several Amperes and allow for very compact vacuum
setups, useful in quantum optics in general, and especially for quantum
information and quantum simulations using miniaturized traps for ions or
neutral atoms. Such printed circuits can also be useful as pure in-vacuum
devices. We demonstrate a specific interface, which provides eleven current
feedthroughs, more than 70 dc feedthroughs and a feedthrough for radio
frequencies. We achieve a pressure in the low 1e-11mbar range and demonstrate
the full functionality of the interface by trapping chains of cold ytterbium
ions, which requires all of the signals mentioned above being present. In
addition, a versatile multi-channel device for supplying precise time-dependent
voltages has been developed.Comment: 8 pages, 7 figures added references to recent literature about
microwave anipulated ions and fast shuttlin
- …