8,759 research outputs found
An Experimental Microarchitecture for a Superconducting Quantum Processor
Quantum computers promise to solve certain problems that are intractable for
classical computers, such as factoring large numbers and simulating quantum
systems. To date, research in quantum computer engineering has focused
primarily at opposite ends of the required system stack: devising high-level
programming languages and compilers to describe and optimize quantum
algorithms, and building reliable low-level quantum hardware. Relatively little
attention has been given to using the compiler output to fully control the
operations on experimental quantum processors. Bridging this gap, we propose
and build a prototype of a flexible control microarchitecture supporting
quantum-classical mixed code for a superconducting quantum processor. The
microarchitecture is based on three core elements: (i) a codeword-based event
control scheme, (ii) queue-based precise event timing control, and (iii) a
flexible multilevel instruction decoding mechanism for control. We design a set
of quantum microinstructions that allows flexible control of quantum operations
with precise timing. We demonstrate the microarchitecture and microinstruction
set by performing a standard gate-characterization experiment on a transmon
qubit.Comment: 13 pages including reference. 9 figure
A critical look at power law modelling of the Internet
This paper takes a critical look at the usefulness of power law models of the
Internet. The twin focuses of the paper are Internet traffic and topology
generation. The aim of the paper is twofold. Firstly it summarises the state of
the art in power law modelling particularly giving attention to existing open
research questions. Secondly it provides insight into the failings of such
models and where progress needs to be made for power law research to feed
through to actual improvements in network performance.Comment: To appear Computer Communication
Can involving clients in simulation studies help them solve their future problems? A transfer of learning experiment
It is often stated that involving the client in operational research studies increases conceptual learning about a system which can then be applied repeatedly to other, similar, systems. Our study provides a novel measurement approach for behavioural OR studies that aim to analyse the impact of modelling in long term problem solving and decision making. In particular, our approach is the first to operationalise the measurement of transfer of learning from modelling using the concepts of close and far transfer, and overconfidence. We investigate learning in discrete-event simulation (DES) projects through an experimental study. Participants were trained to manage queuing problems by varying the degree to which they were involved in building and using a DES model of a hospital emergency department. They were then asked to transfer learning to a set of analogous problems. Findings demonstrate that transfer of learning from a simulation study is difficult, but possible. However, this learning is only accessible when sufficient time is provided for clients to process the structural behaviour of the model. Overconfidence is also an issue when the clients who were involved in model building attempt to transfer their learning without the aid of a new model. Behavioural OR studies that aim to understand learning from modelling can ultimately improve our modelling interactions with clients; helping to ensure the benefits for a longer term; and enabling modelling efforts to become more sustainable
Ribosome collisions and Translation efficiency: Optimization by codon usage and mRNA destabilization
Individual mRNAs are translated by multiple ribosomes that initiate
translation with a few seconds interval. The ribosome speed is codon dependant,
and ribosome queuing has been suggested to explain specific data for
translation of some mRNAs in vivo. By modelling the stochastic translation
process as a traffic problem, we here analyze conditions and consequences of
collisions and queuing. The model allowed us to determine the on-rate (0.8 to
1.1 initiations per sec) and the time (1 sec) the preceding ribosome occludes
initiation for Escherichia coli lacZ mRNA in vivo. We find that ribosome
collisions and queues are inevitable consequences of a stochastic translation
mechanism that reduce the translation efficiency substantially on natural
mRNAs. The cells minimize collisions by having its mRNAs being unstable and by
a highly selected codon usage in the start of the mRNA. The cost of mRNA
breakdown is offset by the concomitant increase in translational efficiency.Comment: 5 figures, 3 table
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