50 research outputs found
Scalable arrays of micro-Penning traps for quantum computing and simulation
We propose the use of 2-dimensional Penning trap arrays as a scalable
platform for quantum simulation and quantum computing with trapped atomic ions.
This approach involves placing arrays of micro-structured electrodes defining
static electric quadrupole sites in a magnetic field, with single ions trapped
at each site and coupled to neighbors via the Coulomb interaction. We solve for
the normal modes of ion motion in such arrays, and derive a generalized
multi-ion invariance theorem for stable motion even in the presence of trap
imperfections. We use these techniques to investigate the feasibility of
quantum simulation and quantum computation in fixed ion lattices. In
homogeneous arrays, we show that sufficiently dense arrays are achievable, with
axial, magnetron and cyclotron motions exhibiting inter-ion dipolar coupling
with rates significantly higher than expected decoherence. With the addition of
laser fields these can realize tunable-range interacting spin Hamiltonians. We
also show how local control of potentials allows isolation of small numbers of
ions in a fixed array and can be used to implement high fidelity gates. The use
of static trapping fields means that our approach is not limited by power
requirements as system size increases, removing a major challenge for scaling
which is present in standard radio-frequency traps. Thus the architecture and
methods provided here appear to open a path for trapped-ion quantum computing
to reach fault-tolerant scale devices.Comment: 21 pages, 10 figures Changes include adding section IX
(Implementation Example) and substantially rewriting section X (Scaling
Robust dynamical exchange cooling with trapped ions
We investigate theoretically the possibility for robust and fast cooling of a
trapped atomic ion by transient interaction with a pre-cooled ion. The
transient coupling is achieved through dynamical control of the ions'
equilibrium positions. To achieve short cooling times we make use of shortcuts
to adiabaticity by applying invariant-based engineering. We design these to
take account of imperfections such as stray fields, and trap frequency offsets.
For settings appropriate to a currently operational trap in our laboratory, we
find that robust performance could be achieved down to motional cycles,
comprising for ions with a trap
frequency. This is considerably faster than can be achieved using laser cooling
in the weak coupling regime, which makes this an attractive scheme in the
context of quantum computing.Comment: 34 pages, 9 figures; added reference, changed title to emphasize
robustnes
Integrated optical multi-ion quantum logic
Practical and useful quantum information processing (QIP) requires
significant improvements with respect to current systems, both in error rates
of basic operations and in scale. Individual trapped-ion qubits' fundamental
qualities are promising for long-term systems, but the optics involved in their
precise control are a barrier to scaling. Planar-fabricated optics integrated
within ion trap devices can make such systems simultaneously more robust and
parallelizable, as suggested by previous work with single ions. Here we use
scalable optics co-fabricated with a surface-electrode ion trap to achieve
high-fidelity multi-ion quantum logic gates, often the limiting elements in
building up the precise, large-scale entanglement essential to quantum
computation. Light is efficiently delivered to a trap chip in a cryogenic
environment via direct fibre coupling on multiple channels, eliminating the
need for beam alignment into vacuum systems and cryostats and lending
robustness to vibrations and beam pointing drifts. This allows us to perform
ground-state laser cooling of ion motion, and to implement gates generating
two-ion entangled states with fidelities . This work demonstrates
hardware that reduces noise and drifts in sensitive quantum logic, and
simultaneously offers a route to practical parallelization for high-fidelity
quantum processors. Similar devices may also find applications in neutral atom
and ion-based quantum-sensing and timekeeping
"‘We just want to be treated with respect!’: Using restorative approaches and the dramatic arts to build positive relationships between the police and young people"
This article explores the application of an ambitious arts-based restorative intervention that has been applied in a direct response to perceived issues with procedural justice, legitimacy and community relations between police and young people. The research focuses on a series of Youth Forums that took place in the West of England, employed as an attempt to improve strained relationships between both parties. It reports on detailed ethnographic research of the Forum processes and procedures presenting this primary evidence in light of the existing literature on police legitimacy and procedural justice in police-youth encounters. The findings suggest that community-based arts programmes can be a powerful and effective tool for challenging entrenched views with the potential to improve future encounters between police and young people; and that the relevance and effectiveness of arts-based interventions can be increased by combining with restorative justice principles