15 research outputs found
Generating distributed entanglement from electron currents
This work is partially supported by a Royal Society University Research FellowshipSeveral recent experiments have demonstrated the viability of a passive device that can generate spin-entangled currents in two separate leads. However, manipulation and measurement of individual flying qubits in a solid state system has yet to be achieved. This is particularly difficult when a macroscopic number of these indistinguishable qubits are present. In order to access such an entangled current resource, we therefore show how to use it to generate distributed, static entanglement. The spatial separation between the entangled static pair can be much higher than that achieved by only exploiting the tunnelling effects between quantum dots. Our device is completely passive, and requires only weak Coulomb interactions between static and flying spins. We show that the entanglement generated is robust to decoherence for large enough currents.Publisher PDFPeer reviewe
Experimental Hamiltonian Identification for Qubits subject to Multiple Independent Control Mechanisms
We consider a qubit subject to various independent control mechanisms and
present a general strategy to identify both the internal Hamiltonian and the
interaction Hamiltonian for each control mechanism, relying only on a single,
fixed readout process such as measurements.Comment: submitted to Proceedings of the QCMC04 (4 pages RevTeX, 5 figures
Measurement-based approach to entanglement generation in coupled quantum dots
Measurements provide a novel mechanism for generating the entanglement
resource necessary for performing scalable quantum computation. Recently, we
proposed a method for performing parity measurements in a coupled quantum dot
system. In this paper we generalise this scheme and perform a comprehensive
analytic and numerical study of environmental factors. We calculate the effects
of possible error sources including non-ideal photon detectors, ineffective
spin-selective excitation and dot distinguishability (both spatial and
spectral). Furthermore, we present an experimental approach for verifying the
success of the parity measurement
Snakes of Telangana: An annotated checklist with new locality records and notes on natural history
With every growing human population and the resultant shrinkage of natural habitats, snakes are frequently encountered in and around human settlements, leading to widespread human-wildlife conflict. Conservation efforts involve rescue & relocation of 'stray' snakes, to mitigate snakebites, human deaths & snake mortality. We utilized snake rescue data of Friends of Snakes Society, Hyderabad, Telangana, recorded between the years 1995 and 2020, to present an annotated snake checklist for Telangana, along with their distribution. Further, opportunistic encounters and temporary captive care of the rescued species yielded significant insights into habitat preferences, dietary choices, aposematic responses, breeding cycles, etc., of various species of this region
Electronic excitation dynamics in multichromophoric systems described via a polaron-representation master equation
We derive a many-site version of the non-Markovian time-convolutionless
polaron master equation [S. Jang et al., J. Chem Phys. 129, 101104 (2008)] to
describe electronic excitation dynamics in multichromophoric systems. By
treating electronic and vibrational degrees of freedom in a combined frame
(polaron frame), this theory is capable of interpolating between weak and
strong exciton-phonon coupling and is able to account for initial
non-equilibrium bath states and spatially correlated environments. Besides
outlining a general expression for the expected value of any electronic system
observable in the original frame, we also discuss implications of the Markovian
and secular approximations highlighting that they need not hold in the
untransformed frame despite being strictly satisfied in the polaron frame. The
key features of the theory are illustrated using as an example a four-site
subsystem of the Fenna-Mathew-Olson light-harvesting complex. For a spectral
density including a localised high-energy mode, we show that oscillations of
site populations may only be observed when non-equilibrium bath effects are
taken into account. Furthermore, we illustrate how this formalism allows us to
identify the electronic or vibrational origin of the oscillatory dynamics.Comment: 13 pages, 6 figures; minor corrections made; accepted for publication
in Journal of Chemical Physic
Large Spin Entangled Current from a Passive Device
We show that a large entangled current can be produced from a very simple
passive device: a cluster of three resonant quantum dots, tunnel coupled to one
input lead and two output leads. The device can function in a `clean' mode,
when almost all emitted electrons are paired in Bell states, or a `dirty' mode
with a far higher emission rate but a significant portion of non-entangled
electrons. Subsequent charge detection can enhance performance by identifying
the pairs that are most likely to be entangled. The device is robust to
specific choice of system parameters and therefore lends itself to immediate
experimental demonstration. Applications include quantum repeaters and
unconditionally secure interfaces.Comment: 9 pages, 4 figures; Minor corrections made to text and now submitted
to New Journal of Physic
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
Generating distributed entanglement from electron currents
Several recent experiments have demonstrated the viability of a passive
device that can generate spin-entangled currents in two separate leads.
However, manipulation and measurement of individual flying qubits in a solid
state system has yet to be achieved. This is particularly difficult when a
macroscopic number of these indistinguishable qubits are present. In order to
access such an entangled current resource, we therefore show how to use it to
generate distributed, static entanglement. The spatial separation between the
entangled static pair can be much higher than that achieved by only exploiting
the tunnelling effects between quantum dots. Our device is completely passive,
and requires only weak Coulomb interactions between static and flying spins. We
show that the entanglement generated is robust to decoherence for large enough
currents.Comment: 13 pages, 7 figure
LES of transient turbulent flow in a pipe
Parity measurements on qubits can generate the entanglement resource necessary for scalable quantum computation. Here we describe a method for fast optical parity measurements on electron spin qubits within coupled quantum dots. The measurement scheme, which can be realized with existing technology, consists of the optical excitation of excitonic states followed by monitored relaxation. Conditional on the observation of a photon, the system is projected into the odd/even-parity subspaces. Our model incorporates all the primary sources of error, including detector inefficiency, effects of spatial separation and nonresonance of the dots, and also unwanted excitations. Through an analytical treatment we establish that the scheme is robust to such effects. Two applications are presented: a realization of a controlled-NOT gate, and a technique for growing large scale graph states