Realistic fast quantum gates with hot trapped ions

The "pushing gate" proposed by Cirac and Zoller in 2000 for quantum logic in ion traps is discussed, in which a force is used to give a controlled push to a pair of trapped ions and thus realize a phase gate. The original proposal had a weakness in that it involved a hidden extreme sensitivity to the size of the force. Also, the physical origin of this force was not fully addressed. Here, we discuss the sensitivity and present a way to avoid it by choosing the spatial form of the pushing force in an optimal way. We also analyse the effect of imperfections in a pair of pi pulses which are used to implement a "spin-echo" to cancel correlated errors. We present a physical model for the force, namely the dipole force, and discuss the impact of unwanted photon scattering, and of finite temperature of the ions. The main effect of the temperature is to blur the phase of the gate owing to the ions exploring a range of values of the force. When the distance scale of the force profile is smaller than the ion separation, this effect is more important than the high-order terms in the Coulomb repulsion which were originally discussed. Overall, we find that whereas the "pushing gate" is not as resistant to imperfections as was supposed, it remains a significant candidate for ion trap quantum computing since it does not require ground state cooling, and in some cases it does not require the Lamb-Dicke limit, while the gate rate is fast, close to (rather than small compared to) the trap vibrational frequency.Comment: 24 pages, 9 figures, revtex

Learning Feature Detectors Using Genetic Programming With Multiple Sensors

In this thesis, we describe the use of Genetic Programming (GP) to learn obstacle detectors to be used for obstacle avoidance on a mobile robot. The first group of experiments focus on learning visual feature detectors for this task. We provide experimental results across a number of different environments, each with different characteristics, and draw conclusions about the performance of the learned feature detector and the training data used to learn such detectors. We also explore the utility of seeding the initial population with previously evolved individuals and subtrees, and discuss the performance of the resulting individuals. We then include sensory data from a laser range-finder and a camera and discuss the performance of resulting individuals as we use just laser data, just image data, and both in combination

The 'new normal' and 'new normalisations' in early childhood education policy in Aotearoa New Zealand: Learnings from Covid-19

When New Zealand entered pandemic alert level 3 and early childhood centres were being ‘nudged’ to re-open in order to offer support for parents returning to work, the Ministry of Health advised both Early Childhood centres and parents that children were not at risk of catching or spreading the virus. Fast-forward to Level 1 and the Ministry of Health has advised that an infant, who arrived into the country from overseas together with its parents, had the virus and was in a managed quarantine. This paper discusses this apparent policy contradiction between guidelines and evidence by collecting and analysing discourses that the nation has received from government agencies regarding children and early childhood education. This paper uses these discourses to explore the 'body' of knowledge regarding childhood and early childhood education, discourses that make childhood and early childhood education possible. We then apply a range of theoretical and conceptual tools to suggest some possible conditions of early childhood education (leading up to, during, and post-Covid-19). We employ health and medical metaphors to highlight ongoing tensions for early childhood education as a patient for whom neither education nor health Ministries take sufficient responsibility. The use of a health as a metaphor additionally focuses this paper on the new ‘normal’ of early childhood education and education policy

The 'new normal' and 'new normalisations' in early childhood education policy in Aotearoa New Zealand: Learnings from Covid-19

When New Zealand entered pandemic alert level 3 and early childhood centres were being ‘nudged’ to re-open in order to offer support for parents returning to work, the Ministry of Health advised both Early Childhood centres and parents that children were not at risk of catching or spreading the virus. Fast-forward to Level 1 and the Ministry of Health has advised that an infant, who arrived into the country from overseas together with its parents, had the virus and was in a managed quarantine. This paper discusses this apparent policy contradiction between guidelines and evidence by collecting and analysing discourses that the nation has received from government agencies regarding children and early childhood education. This paper uses these discourses to explore the 'body' of knowledge regarding childhood and early childhood education, discourses that make childhood and early childhood education possible. We then apply a range of theoretical and conceptual tools to suggest some possible conditions of early childhood education (leading up to, during, and post-Covid-19). We employ health and medical metaphors to highlight ongoing tensions for early childhood education as a patient for whom neither education nor health Ministries take sufficient responsibility. The use of a health as a metaphor additionally focuses this paper on the new ‘normal’ of early childhood education and education policy

Relational Approach to Knowledge Engineering for POMDP-based Assistance Systems as a Translation of a Psychological Model

Assistive systems for persons with cognitive disabilities (e.g. dementia) are difficult to build due to the wide range of different approaches people can take to accomplishing the same task, and the significant uncertainties that arise from both the unpredictability of client's behaviours and from noise in sensor readings. Partially observable Markov decision process (POMDP) models have been used successfully as the reasoning engine behind such assistive systems for small multi-step tasks such as hand washing. POMDP models are a powerful, yet flexible framework for modelling assistance that can deal with uncertainty and utility. Unfortunately, POMDPs usually require a very labour intensive, manual procedure for their definition and construction. Our previous work has described a knowledge driven method for automatically generating POMDP activity recognition and context sensitive prompting systems for complex tasks. We call the resulting POMDP a SNAP (SyNdetic Assistance Process). The spreadsheet-like result of the analysis does not correspond to the POMDP model directly and the translation to a formal POMDP representation is required. To date, this translation had to be performed manually by a trained POMDP expert. In this paper, we formalise and automate this translation process using a probabilistic relational model (PRM) encoded in a relational database. We demonstrate the method by eliciting three assistance tasks from non-experts. We validate the resulting POMDP models using case-based simulations to show that they are reasonable for the domains. We also show a complete case study of a designer specifying one database, including an evaluation in a real-life experiment with a human actor

Formalizing Kant’s Rules

This paper formalizes part of the cognitive architecture that Kant develops in the Critique of Pure Reason. The central Kantian notion that we formalize is the rule. As we interpret Kant, a rule is not a declarative conditional stating what would be true if such and such conditions hold. Rather, a Kantian rule is a general procedure, represented by a conditional imperative or permissive, indicating which acts must or may be performed, given certain acts that are already being performed. These acts are not propositions; they do not have truth-values. Our formalization is related to the input/ output logics, a family of logics designed to capture relations between elements that need not have truth-values. In this paper, we introduce KL3 as a formalization of Kant’s conception of rules as conditional imperatives and permissives. We explain how it differs from standard input/output logics, geometric logic, and first-order logic, as well as how it translates natural language sentences not well captured by first-order logic. Finally, we show how the various distinctions in Kant’s much-maligned Table of Judgements emerge as the most natural way of dividing up the various types and sub-types of rule in KL3. Our analysis sheds new light on the way in which normative notions play a fundamental role in the conception of logic at the heart of Kant’s theoretical philosophy

Topological Hunds rules and the electronic properties of a triple lateral quantum dot molecule

We analyze theoretically and experimentally the electronic structure and charging diagram of three coupled lateral quantum dots filled with electrons. Using the Hubbard model and real-space exact diagonalization techniques we show that the electronic properties of this artificial molecule can be understood using a set of topological Hunds rules. These rules relate the multi-electron energy levels to spin and the inter-dot tunneling $t$, and control charging energies. We map out the charging diagram for up to N=6 electrons and predict a spin-polarized phase for two holes. The theoretical charging diagram is compared with the measured charging diagram of the gated triple-dot device.Comment: 31 pages, 7 figures, accepted to March 15, 2007 issue of Phys. Rev. B, vol. 7

A large conductance, Ca2+-activated K+ channel in a human lung epithelial cell line (A549)

AbstractA large conductance, Ca2+-activated K+ channel in a human lung epithelial cell line (A549) was identified using the single channel patch clamp technique. Channel conductance was 242±33 pS (n=67) in symmetrical KCl (140 mM). The channel was activated by membrane depolarization and increased cytosolic Ca2+. High selectivity was observed for K+ over Rb+(0.49)>Cs+(0.14)>Na+(0.09). Open probability was significantly decreased by Ba2+ (5 mM) and quinidine (5 mM) to either surface, but TEA (5 mM) was only effective when added to the external surface. All effects were reversible. Increasing cytosolic Ca2+ concentration from 10−7 to 10−6 M caused an increase in open probability from near zero to fully activated. ATP decreased open probability at ∼2 mM, but the effect was variable. The channel was almost always observed together with a smaller conductance channel, although they could both be seen individually. We conclude that A549 cells contain large conductance Ca2+-activated K+ channels which could explain a major fraction of the K+ conductance in human alveolar epithelial membranes