83 research outputs found
Adaptive versus non-adaptive strategies for quantum channel discrimination
We provide a simple example that illustrates the advantage of adaptive over
non-adaptive strategies for quantum channel discrimination. In particular, we
give a pair of entanglement-breaking channels that can be perfectly
discriminated by means of an adaptive strategy that requires just two channel
evaluations, but for which no non-adaptive strategy can give a perfect
discrimination using any finite number of channel evaluations.Comment: 11 page
Quantum state restoration and single-copy tomography
Given a single copy of an n qubit quantum state |psi>, the no-cloning theorem
greatly limits the amount of information which can be extracted from it.
Moreover, given only a procedure which verifies the state, for example a
procedure which measures the operator |psi> in
time polynomial in n . In this paper, we consider the scenario in which we are
given both a single copy of |psi> and the ability to verify it. We show that in
this setting, we can do several novel things efficiently. We present a new
algorithm that we call quantum state restoration which allows us to extend a
large subsystem of |psi> to the full state, and in turn this allows us to copy
small subsystems of |psi>. In addition, we present algorithms that can perform
tomography on small subsystems of |psi>, and we show how to use these
algorithms to estimate the statistics of any efficiently implementable POVM
acting on |psi> in time polynomial in the number of outcomes of the POVM.Comment: edited for clarity; 13 pages, 1 figur
Multiparty hierarchical quantum-information splitting
We propose a scheme for multiparty hierarchical quantum-information splitting
(QIS) with a multipartite entangled state, where a boss distributes a secret
quantum state to two grades of agents asymmetrically. The agents who belong to
different grades have different authorities for recovering boss's secret.
Except for boss's Bell-state measurement, no nonlocal operation is involved.
The presented scheme is also shown to be secure against eavesdropping. Such a
hierarchical QIS is expected to find useful applications in the field of modern
multipartite quantum cryptography.Comment: 6 pages, 2 table
Shared computational principles for language processing in humans and deep language models
Departing from traditional linguistic models, advances in deep learning have resulted in a new type of predictive (autoregressive) deep language models (DLMs). Using a self-supervised next-word prediction task, these models generate appropriate linguistic responses in a given context. In the current study, nine participants listened to a 30-min podcast while their brain responses were recorded using electrocorticography (ECoG). We provide empirical evidence that the human brain and autoregressive DLMs share three fundamental computational principles as they process the same natural narrative: (1) both are engaged in continuous next-word prediction before word onset; (2) both match their pre-onset predictions to the incoming word to calculate post-onset surprise; (3) both rely on contextual embeddings to represent words in natural contexts. Together, our findings suggest that autoregressive DLMs provide a new and biologically feasible computational framework for studying the neural basis of language
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
The Complex Interplay between Nevi and Melanoma: Risk Factors and Precursors
One effort to combat the rising incidence of malignant melanoma is focused on early detection by the clinical and dermoscopic screening of melanocytic nevi. However, the interaction between nevi, which are congenital or acquired benign melanocytic proliferations, and melanoma is still enigmatic. On the one hand, the majority of melanomas are thought to form de novo, as only a third of primary melanomas are associated with a histologically identifiable nevus precursor. On the other hand, an increased number of melanocytic nevi is a strong risk factor for developing melanoma, including melanomas that do not derive from nevi. The formation of nevi is modulated by diverse factors, including pigmentation, genetic risk factors, and environmental sun exposure. While the molecular alterations that occur during the progression of a nevus to melanoma have been well characterized, many unanswered questions remain surrounding the process of nevus to melanoma evolution. In this review, we discuss clinical, histological, molecular, and genetic factors that influence nevus formation and progression to melanoma
CIRCADIAN CLOCK ASSOCIATED1 Transcript Stability and the Entrainment of the Circadian Clock in Arabidopsis1[W][OA]
The circadian clock is an endogenous mechanism that generates rhythms with an approximately 24-h period and enables plants to predict and adapt to daily and seasonal changes in their environment. These rhythms are generated by molecular oscillators that in Arabidopsis (Arabidopsis thaliana) have been shown to consist of interlocking feedback loops involving a number of elements. An important characteristic of circadian oscillators is that they can be entrained by daily environmental changes in light and temperature. Previous work has shown that one possible entrainment point for the Arabidopsis oscillator is the light-mediated regulation of expression of one of the oscillator genes, CIRCADIAN CLOCK ASSOCIATED1 (CCA1). In this article, we have used transgenic plants with constitutive CCA1 expression to show that light also regulates CCA1 transcript stability. Our experiments show that CCA1 messenger RNA is relatively stable in the dark and in far-red light but has a short half-life in red and blue light. Furthermore, using transgenic plants expressing chimeric CCA1 constructs, we demonstrate that the instability determinants in CCA1 transcripts are probably located in the coding region. We suggest that the combination of light regulation of CCA1 transcription and CCA1 messenger RNA degradation is important for ensuring that the Arabidopsis circadian oscillator is accurately entrained by environmental changes
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