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2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Guillermo Ballesteros ◽  
Sebastián Céspedes ◽  
Luca Santoni

Abstract We study the generation of a large power spectrum, necessary for primordial black hole formation, within the effective theory of single-field inflation. The mechanisms we consider include a transition into a ghost-inflation-like phase and scenarios where an exponentially growing mode is temporarily turned on. In the cases we discuss, the enhancement in the power spectrum results from either a swift change in some effective coupling or a modification of the dispersion relation for the perturbations, while the background evolution remains unchanged and approximately de Sitter throughout inflation. The robustness of the results is guaranteed thanks to a weakly broken galileon symmetry, which protects the effective couplings against large quantum corrections. We discuss how the enhancement of the power spectrum is related to the energy scale of the operators with weakly broken galileon invariance, and study the limits imposed by strong coupling and the validity of the perturbative expansion.


Entropy ◽  
2021 ◽  
Vol 24 (1) ◽  
pp. 49
Author(s):  
Dmitry Makarov ◽  
Yuliana Tsykareva

It is well known that the waveguide beam splitter can be used as a source for the quantum entanglement of photons. The analysis of such quantum entanglement is a difficult problem even for monochromatic photons, since the system under study is multiparametric. This paper will show that quantum entanglement can be represented in a simple form not only for monochromatic photons but also for non-monochromatic ones. It will be shown that quantum entanglement for non-monochromatic photons can be very different from monochromatic photons, which can be used to create large quantum entanglement.


Author(s):  
Wai-Keong Mok ◽  
Leong-Chuan Kwek

The ability to control the flow of quantum information deterministically is useful for scaling up quantum computation. In this paper, we demonstrate a controllable quantum switchboard which directs the teleportation protocol to one of two targets, fully dependent on the sender’s choice. The quantum switchboard additionally acts as a optimal quantum cloning machine. We also provide a physical implementation of the proposal using a coupled-cavity array. The proposed switchboard can be utilized for the efficient routing of quantum information in a large quantum network.


Author(s):  
Steven Carlip

Abstract Wheeler's conjectured "spacetime foam" -- large quantum fluctuations of spacetime at the Planck scale -- could have important implications for quantum gravity, perhaps even explaining why the cosmological constant seems so small. Here I explore this problem in a midisuperspace model consisting of metrics with local spherical symmetry. Classically, an infinite class of ``foamy'' initial data can be constructed, in which cancellations between expanding and contracting regions lead to a small average expansion even if Λ is large. Quantum mechanically, the model admits corresponding stationary states, for which the probability current is also nearly zero. These states appear to describe a self-reproducing spacetime foam with very small average expansion, effectively hiding the cosmological constant.


Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2743
Author(s):  
I-Hsiang Wang ◽  
Po-Yu Hong ◽  
Kang-Ping Peng ◽  
Horng-Chih Lin ◽  
Thomas George ◽  
...  

Semiconductor-based quantum registers require scalable quantum-dots (QDs) to be accurately located in close proximity to and independently addressable by external electrodes. Si-based QD qubits have been realized in various lithographically-defined Si/SiGe heterostructures and validated only for milli-Kelvin temperature operation. QD qubits have recently been explored in germanium (Ge) materials systems that are envisaged to operate at higher temperatures, relax lithographic-fabrication requirements, and scale up to large quantum systems. We report the unique scalability and tunability of Ge spherical-shaped QDs that are controllably located, closely coupled between each another, and self-aligned with control electrodes, using a coordinated combination of lithographic patterning and self-assembled growth. The core experimental design is based on the thermal oxidation of poly-SiGe spacer islands located at each sidewall corner or included-angle location of Si3N4/Si-ridges with specially designed fanout structures. Multiple Ge QDs with good tunability in QD sizes and self-aligned electrodes were controllably achieved. Spherical-shaped Ge QDs are closely coupled to each other via coupling barriers of Si3N4 spacer layers/c-Si that are electrically tunable via self-aligned poly-Si or polycide electrodes. Our ability to place size-tunable spherical Ge QDs at any desired location, therefore, offers a large parameter space within which to design novel quantum electronic devices.


2021 ◽  
Author(s):  
Kristen Csenkey ◽  
Nina Bindel

Threats against security in the Internet often have a wide-range and can have serious impacts within society. Large quantum computers will be able to break the cryptographic algorithms used to ensure security today, which is known as the quantum threat. Quantum threats are multi-faceted and very complex cybersecurity issues. We use assemblage theory to explore the complexities associated with these threats, including how they are understood within policy and strategy. It is in this way that we explore how the governance of the quantum threat is made visible. Generally, the private and academic sector have been a primary driver in this field, but other actors(especially states) have begun to grapple with the threat and have begun to understand the relation to defence challenges, and pathways to cooperation in order to prepare against the threat. This may pose challenges for traditional avenues of defence cooperation as states attempt to understand and manage the associated technologies and perceived threats. We examine how traditionally cooperating allies attempt to govern the quantum threat by focusing on Australia, Canada, the European Union (EU), New Zealand, the United Kingdom (UK), and the United States (US). We explore the linkages within post-quantum cryptographic assemblages and identify several governmental interventions as attempts to understand and manage the threat and associated technologies. In examining over 40 policy and strategy-related documents between traditionally defence cooperating allies, we identify six main linkages: Infrastructure, Standardization, Education, Partnerships, Economy, and Defence. These linkages highlight the governmental interventions to govern through standardization and regulation as a way to define to contours of the quantum threat.


Author(s):  
Luis Alvarez-Gaume ◽  
Domenico Orlando ◽  
Susanne Reffert

2021 ◽  
Vol 8 (2) ◽  
pp. 1
Author(s):  
Larysa Botha ◽  
Renier Steyn

Background: Psychological contracts, and particularly the honouring of these contracts – are central to employee behaviour and organisational success. The interest of academics and practitioners in this construct is therefore understandable. However, due to the immense amount of information on the topic, a comprehensive review of the literature is necessary. Aim: The aim of this article is to present a critical review on the conceptualisation of the psychological contract, distilling and operationalising the concept, to ensure that debate and future research are linked to a dominant body of knowledge. Setting: Present literature on psychological contracts is fragmented as no conceptual standardisation exists. Method: A comprehensive literature review was conducted to obtain a large quantum of conceptualisations of the construct and evaluate these for breadth of adoption, consensus, and operationalisation. Results: After reviewing reputable sources published between 1960 and 2020, a standard definition proposed, the most recognised typologies specified, and sound measures identified. It was found that Rousseau’s (1995) definition and typologies (transactional and relational contracts) are still widely used, and that the measuring scale for transactional and relational contracts by Millward and Hopkins (1998) demonstrates good psychometric properties and broadly utilised. Conclusion: Since its inception, several amended definitions, typologies, and measurement of the psychological contract have been presented. Nonetheless, the original conceptualisations still seem to prevail. Managerial implications: Researchers and practitioners are now aware of the most widely adopted definitions, typologies and measuring instruments relating to psychological contract and these should guide them in future discussions and research in the field.


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