1,556 research outputs found
Deterministic reordering of 40Ca+ ions in a linear segmented Paul trap
In the endeavour to scale up the number of qubits in an ion-based quantum
computer several groups have started to develop miniaturized ion traps for
extended spatial control and manipulation of the ions. Shuttling and separation
of ion strings have been the foremost issues in linear-trap arrangements and
some prototypes of junctions have been demonstrated for the extension of ion
motion to two dimensions (2D). While junctions require complex trap structures,
small extensions to the 1D motion can be accomplished in simple linear trap
arrangements. Here, control of the extended field in a planar, linear chip trap
is used to shuttle ions in 2D. With this approach, the order of ions in a
string is deterministically reversed. Optimized potentials are theoretically
derived and simulations show that the reordering can be carried out
adiabatically. The control over individual ion positions in a linear trap
presents a new tool for ion-trap quantum computing. The method is also expected
to work with mixed crystals of different ion species and as such could have
applications for sympathetic cooling of an ion string.Comment: 18 pages, 9 figures. Added section on possibility of adiabatic turn.
Added appendix on point charge model. Other minor alterations/clarifications.
Version now published (http://www.iop.org/EJ/abstract/1367-2630/11/10/103008
Realisation of a programmable two-qubit quantum processor
The universal quantum computer is a device capable of simulating any physical
system and represents a major goal for the field of quantum information
science. Algorithms performed on such a device are predicted to offer
significant gains for some important computational tasks. In the context of
quantum information, "universal" refers to the ability to perform arbitrary
unitary transformations in the system's computational space. The combination of
arbitrary single-quantum-bit (qubit) gates with an entangling two-qubit gate is
a gate set capable of achieving universal control of any number of qubits,
provided that these gates can be performed repeatedly and between arbitrary
pairs of qubits. Although gate sets have been demonstrated in several
technologies, they have as yet been tailored toward specific tasks, forming a
small subset of all unitary operators. Here we demonstrate a programmable
quantum processor that realises arbitrary unitary transformations on two
qubits, which are stored in trapped atomic ions. Using quantum state and
process tomography, we characterise the fidelity of our implementation for 160
randomly chosen operations. This universal control is equivalent to simulating
any pairwise interaction between spin-1/2 systems. A programmable multi-qubit
register could form a core component of a large-scale quantum processor, and
the methods used here are suitable for such a device.Comment: 7 pages, 4 figure
Sideband cooling and coherent dynamics in a microchip multi-segmented ion trap
Miniaturized ion trap arrays with many trap segments present a promising
architecture for scalable quantum information processing. The miniaturization
of segmented linear Paul traps allows partitioning the microtrap in different
storage and processing zones. The individual position control of many ions -
each of them carrying qubit information in its long-lived electronic levels -
by the external trap control voltages is important for the implementation of
next generation large-scale quantum algorithms.
We present a novel scalable microchip multi-segmented ion trap with two
different adjacent zones, one for the storage and another dedicated for the
processing of quantum information using single ions and linear ion crystals: A
pair of radio-frequency driven electrodes and 62 independently controlled DC
electrodes allows shuttling of single ions or linear ion crystals with
numerically designed axial potentials at axial and radial trap frequencies of a
few MHz. We characterize and optimize the microtrap using sideband spectroscopy
on the narrow S1/2 D5/2 qubit transition of the 40Ca+ ion, demonstrate
coherent single qubit Rabi rotations and optical cooling methods. We determine
the heating rate using sideband cooling measurements to the vibrational ground
state which is necessary for subsequent two-qubit quantum logic operations. The
applicability for scalable quantum information processing is proven.Comment: 17 pages, 11 figure
Microfabricated Ion Traps
Ion traps offer the opportunity to study fundamental quantum systems with
high level of accuracy highly decoupled from the environment. Individual atomic
ions can be controlled and manipulated with electric fields, cooled to the
ground state of motion with laser cooling and coherently manipulated using
optical and microwave radiation. Microfabricated ion traps hold the advantage
of allowing for smaller trap dimensions and better scalability towards large
ion trap arrays also making them a vital ingredient for next generation quantum
technologies. Here we provide an introduction into the principles and operation
of microfabricated ion traps. We show an overview of material and electrical
considerations which are vital for the design of such trap structures. We
provide guidance in how to choose the appropriate fabrication design, consider
different methods for the fabrication of microfabricated ion traps and discuss
previously realized structures. We also discuss the phenomenon of anomalous
heating of ions within ion traps, which becomes an important factor in the
miniaturization of ion traps
Arrays of individually controlled ions suitable for two-dimensional quantum simulations
A precisely controlled quantum system may reveal a fundamental understanding of another, less accessible system of interest. A universal quantum computer is currently out of reach, but an analogue quantum simulator that makes relevant observables, interactions and states of a quantum model accessible could permit insight into complex dynamics. Several platforms have been suggested and proof-of-principle experiments have been conducted. Here, we operate two-dimensional arrays of three trapped ions in individually controlled harmonic wells forming equilateral triangles with side lengths 40 and 80 μm. In our approach, which is scalable to arbitrary two-dimensional lattices, we demonstrate individual control of the electronic and motional degrees of freedom, preparation of a fiducial initial state with ion motion close to the ground state, as well as a tuning of couplings between ions within experimental sequences. Our work paves the way towards a quantum simulator of two-dimensional systems designed at will
The development of microfabricated ion traps towards quantum information and simulation
Trapped ions within Paul traps have shown to be a promising architecture in the realisation
of a quantum information processor together with the ability of providing quantum
simulations. Linear Paul traps have demonstrated long coherence times with ions being
well isolated from the environment, single and multi-qubit gates and the high fidelity
detection of states. The scalability to large number of qubits, incorporating all the previous
achievements requires an array of linear ion traps. Microfabrication techniques allow
for fabrication and micron level accuracy of the trap electrode dimensions through photolithography
techniques.
The first part of this thesis presents the experiential setup and trapping of Yb+ ions
needed to test large ion trap arrays. This include vacuum systems that can host advanced
symmetric and asymmetric ion traps with up to 90 static voltage control electrodes.
Demonstration of a single trapped Yb+ ion within a two-layer macroscopic ion
trap is presented. with an ion-electrode distance of 310(10) ÎĽm. The anomalous heating
rate and spectral noise density of the trap was measured, a main form of decoherence
within ion traps.
The second half of this thesis presents the design and fabrication of multi-layer asymmetric
ion traps. This allows for isolated electrodes that cannot be accessed via surface
pathways, allowing for higher density of electrodes as well as creating novel trap designs
that allow for the potential of quantum simulations to be demonstrated. These include
two-dimensional lattices and ring trap designs in which the isolated electrodes provide
more control in the ion position.
For the microfabrication of these traps I present a novel high-aspect ratio electroplated electrode design that provides shielding of the dielectric layer. This provides a means to mitigate stray electric field due to charge build up on the dielectric surfaces. Electrical testing of the trap structures was performed to test bulk breakdown and surface flashover of the ion trap architectures. Results showed sufficient isolation between electrodes for both radio frequency and static breakdown. Surface flashover voltage measurements over the dielectric layer showed an improvement of more than double over previous results using
a new fabrication technique. This will allow for more powerful ion trap chips needed for the next generation of microfabricated ion trap arrays for scalable quantum technologies
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