1,374 research outputs found
Development and operation of the twin radio frequency single electron transistor for solid state qubit readout
Ultra-sensitive detectors and readout devices based on the radio frequency
single electron transistor (rf-SET) combine near quantum-limited sensitivity
with fast operation. Here we describe a twin rf-SET detector that uses two
superconducting rf-SETs to perform fast, real-time cross-correlated
measurements in order to distinguish sub-electron signals from charge noise on
microsecond time-scales. The twin rf-SET makes use of two tuned resonance
circuits to simultaneously and independently address both rf-SETs using
wavelength division multiplexing (WDM) and a single cryogenic amplifier. We
focus on the operation of the twin rf-SET as a charge detector and evaluate the
cross-talk between the two resonance circuits. Real time suppression of charge
noise is demonstrated by cross correlating the signals from the two rf-SETs.
For the case of simultaneous operation, the rf-SETs had charge sensitivities of
and .Comment: Updated version, including new content. Comments most welcome:
[email protected] or [email protected]
The Evolution of X-ray Bursts in the "Bursting Pulsar" GRO J1744-28
GRO J1744-28, commonly known as the `Bursting Pulsar', is a low mass X-ray
binary containing a neutron star and an evolved giant star. This system,
together with the Rapid Burster (MXB 1730-33), are the only two systems that
display the so-called Type II X-ray bursts. These type of bursts, which last
for 10s of seconds, are thought to be caused by viscous instabilities in the
disk; however the Type II bursts seen in GRO J1744-28 are qualitatively very
different from those seen in the archetypal Type II bursting source the Rapid
Burster. To understand these differences and to create a framework for future
study, we perform a study of all X-ray observations of all 3 known outbursts of
the Bursting Pulsar which contained Type II bursts, including a population
study of all Type II X-ray bursts seen by RXTE. We find that the bursts from
this source are best described in four distinct phenomena or `classes' and that
the characteristics of the bursts evolve in a predictable way. We compare our
results with what is known for the Rapid Burster and put out results in the
context of models that try to explain this phenomena.Comment: Accepted to MNRAS Aug 17 201
Conducting Effective Research into State Complicity in Human Rights Abuses
This paper explores how to conduct effective research into state complicity in human rights abuses. This type of research is challenging: the secretive nature of state violence presents considerable difficulties for the researcher, in terms of both access to evidence, and the safety and security of the researcher and victims. Recent developments in the methods and types of data available present new opportunities for strengthening research. Drawing on our own experience, specifically our work to map the CIA’s rendition, detention and interrogation programme, we aim to show how we have navigated the difficult terrain of human rights investigation. The paper begins by exploring a number of challenges involved. We then discuss recent developments in human rights investigation techniques, as well as the emerging body of critical scholarship that is beginning to shape this kind of work among practitioners and academics alike. We consider some of the imbalances of power that affect this type of research. We then demonstrate how we tried to embrace new opportunities, while being mindful of the risks involved and the limitations of what we can achieve. We close with some reflections on ways forward for this type of research
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