79 research outputs found
Self-testing through EPR-steering
The verification of quantum devices is an important aspect of quantum information, especially with the emergence of more advanced experimental implementations of quantum computation and secure communication. Within this, the theory of device-independent robust self-testing via Bell tests has reached a level of maturity now that many quantum states and measurements can be verified without direct access to the quantum systems: interaction with the devices is solely classical. However, the requirements for this robust level of verification are daunting and require high levels of experimental accuracy. In this paper we discuss the possibility of self-testing where we only have direct access to one part of the quantum device. This motivates the study of self-testing via EPR-steering, an intermediate form of entanglement verification between full state tomography and Bell tests. Quantum non-locality implies EPR-steering so results in the former can apply in the latter, but we ask what advantages may be gleaned from the latter over the former given that one can do partial state tomography? We show that in the case of self-testing a maximally entangled two-qubit state, or ebit, EPR-steering allows for simpler analysis and better error tolerance than in the case of full device-independence. On the other hand, this improvement is only a constant improvement and (up to constants) is the best one can hope for. Finally, we indicate that the main advantage in self-testing based on EPR-steering could be in the case of self-testing multi-partite quantum states and measurements. For example, it may be easier to establish a tensor product structure for a particular partyâs Hilbert space even if we do not have access to their part of the global quantum system
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Orthographic facilitation in oral vocabulary acquisition
An experiment investigated whether exposure to orthography facilitates oral vocabulary learning. A total of 58 typically developing children aged 8-9 years were taught 12 nonwords. Children were trained to associate novel phonological forms with pictures of novel objects. Pictures were used as referents to represent novel word meanings. For half of the nonwords children were additionally exposed to orthography, although they were not alerted to its presence, nor were they instructed to use it. After this training phase a nonword-picture matching posttest was used to assess learning of nonword meaning, and a spelling posttest was used to assess learning of nonword orthography. Children showed robust learning for novel spelling patterns after incidental exposure to orthography. Further, we observed stronger learning for nonword-referent pairings trained with orthography. The degree of orthographic facilitation observed in posttests was related to children's reading levels, with more advanced readers showing more benefit from the presence of orthography
Rigidity of quantum steering and one-sided device-independent verifiable quantum computation
The relationship between correlations and entanglement has played a major
role in understanding quantum theory since the work of Einstein, Podolsky and
Rosen (1935). Tsirelson (1980) proved that Bell states, shared among two
parties, when measured suitably, achieve the maximum non-local correlations
allowed by quantum mechanics. Conversely, Reichardt, Unger and Vazirani (2013)
showed that observing the maximal correlation value over a sequence of repeated
measurements, implies that the underlying quantum state is close to a tensor
product of maximally entangled states and, moreover, that it is measured
according to an ideal strategy. However, this strong rigidity result comes at a
high price, requiring a large number of entangled pairs to be tested. In this
paper, we present a significant improvement in terms of the overhead by instead
considering quantum steering where the device of the one side is trusted. We
first demonstrate a robust one-sided device-independent version of
self-testing, which characterises the shared state and measurement operators of
two parties up to a certain bound. We show that this bound is optimal up to
constant factors and we generalise the results for the most general attacks.
This leads us to a rigidity theorem for maximal steering correlations. As a key
application we give a one-sided device-independent protocol for verifiable
delegated quantum computation, and compare it to other existing protocols, to
highlight the cost of trust assumptions. Finally, we show that under reasonable
assumptions, the states shared in order to run a certain type of verification
protocol must be unitarily equivalent to perfect Bell states.Comment: Journal version. We acknowledge discussions with Matty J Hoban on his
and Ivan \v{S}upi\'c's independent work on self-testing using quantum
steering, arXiv:1601.0155
Exploring concepts of health with male prisoners in three category-C English prisons
Lay understandings of health and illness have a well established track record and a plethora of research now exists which has examined these issues. However, there is a dearth of research which has examined the perspectives of those who are imprisoned. This paper attempts to address this research gap. The paper is timely given that calls have been made to examine lay perspectives in different geographical locations and a need to re-examine health promotion approaches in prison settings. Qualitative data from thirty-six male sentenced prisoners from three prisons in England were collected. The data was analysed in accordance with Attride-Stirling's (2001) thematic network approach. Although the men's perceptions of health were broadly similar to the general population, some interesting findings emerged which were directly related to prison life and its associated structures. These included access to the outdoors and time out of their prison cell, as well as maintaining relationships with family members through visits. The paper proposes that prisoners' lay views should be given higher priority given that prison health has traditionally been associated with medical treatment and the bio-medical paradigm more generally. It also suggests that in order to fulfil the World Health Organization's (WHO) vision of viewing prisons as health promoting settings, lay views should be recognised to shape future health promotion policy and practice
Can multinational companies foster institutional change and sustainable development in emerging countries? A case study.
Emerging countries present institutional necessities that hinder their sustainable
development. In the face of this challenge, companies, and in particular multinational
companies (MNCs), can foster sustainable development through their corporate social
responsibility (CSR) initiatives. This study focuses on the role of institutional change in
transforming CSR into sustainable development in emerging countries. To this end, we
propose a view of CSR focused on its institutional determinants and outcomes from a
social and developmental perspective. By using quantitative and qualitative data, we
analyse the case of three MNCs from different industries based in Europe and operating in Mexico. The case study shows how firms can stimulate institutional change in
developing economies and contribute to their sustainable development as measured
by the sustainable development goals. Various mechanisms about how this process is
made are devised: institutional entrepreneurship, multistakeholder initiatives, interconnection of different institutional dimensions, and subsidiary entrepreneurship. The case
study highlights the interaction among MNCs, developing countries, and institutions
and how firms' sustainable actions scale up to the macro level.post-print399 K
Robustness and device independence of verifiable blind quantum computing
Recent advances in theoretical and experimental quantum computing bring us
closer to scalable quantum computing devices. This makes the need for protocols
that verify the correct functionality of quantum operations timely and has led
to the field of quantum verification. In this paper we address key challenges
to make quantum verification protocols applicable to experimental
implementations. We prove the robustness of the single server verifiable
universal blind quantum computing protocol of Fitzsimons and Kashefi (2012) in
the most general scenario. This includes the case where the purification of the
deviated input state is in the hands of an adversarial server. The proved
robustness property allows the composition of this protocol with a
device-independent state tomography protocol that we give, which is based on
the rigidity of CHSH games as proposed by Reichardt, Unger and Vazirani (2013).
The resulting composite protocol has lower round complexity for the
verification of entangled quantum servers with a classical verifier and, as we
show, can be made fault tolerant.Comment: Shortly before uploading the first version on the arxiv, the authors
became aware of parallel and independent research by Hajdusek, Perez-Delgado
and Fitzsimons, which also addresses device-independent verifiable blind
quantum computing and appeared the same day on the arxi
Quantum Tasks in Minkowski Space
The fundamental properties of quantum information and its applications to
computing and cryptography have been greatly illuminated by considering
information-theoretic tasks that are provably possible or impossible within
non-relativistic quantum mechanics. I describe here a general framework for
defining tasks within (special) relativistic quantum theory and illustrate it
with examples from relativistic quantum cryptography and relativistic
distributed quantum computation. The framework gives a unified description of
all tasks previously considered and also defines a large class of new questions
about the properties of quantum information in relation to Minkowski causality.
It offers a way of exploring interesting new fundamental tasks and
applications, and also highlights the scope for a more systematic understanding
of the fundamental information-theoretic properties of relativistic quantum
theory
Investigation of the effect of relative humidity on polymers by depth sensing indentation
This article was published in the serial, Journal of Materials Science [© Springer]. The definitive version is available from: http://www.springerlink.com/content/y2g413h8h2l6044m/Stereolithography (SL) resins absorb varying
amounts of moisture dependent on the relative humidities,
which can significantly affect the mechanical properties. In
this work, the influence of relative humidity (RH) on the
mechanical behaviour of an SL resin is investigated using
depth sensing indentation (DSI). The samples were conditioned
by two methods. In the first method, samples were
pre-conditioned at 33.5, 53.8, 75.3 and 84.5% RH using
saturated salt solutions. These preconditioned samples
were tested at 33.5% RH, using a humidity control unit
(HCU) to control RH in the DSI system. In the second
method, samples were conditioned and tested at 33.5, 53.8,
75.3 and 84.5% RH by regulating humidity in the DSI
system using the HCU. Temperature was kept constant at
22.5 C for the conditioning and DSI testing. It was seen
that hardness and modulus decreased with increasing RH
and conditioning time but recovered significantly when
tested after drying. This study demonstrates that RH needs
to be taken into account during the DSI testing of
polymers
Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system
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