scholarly journals Computational Collapse of Quantum State with Application to Oblivious Transfer

2003 ◽  
Vol 10 (37) ◽  
Author(s):  
Claude Crépeau ◽  
Paul Dumais ◽  
Dominic Mayers ◽  
Louis Salvail
Keyword(s):  
Quantum State ◽  
Polynomial Time ◽  
Quantum Measurement ◽  
Oblivious Transfer ◽  
Black Box ◽  
The State ◽  
Natural Question ◽  
Full Information ◽  
Classical Counterpart ◽  
Commitment Scheme

Quantum 2-party cryptography differs from its classical counterpart in at least one important way: Given black-box access to a perfect commitment scheme there exists a secure 1-2 <em>quantum</em> oblivious transfer. This reduction proposed by Crépeau and Kilian was proved secure against any receiver by Yao, in the case where perfect commitments are used. However, quantum commitments would normally be based on computational assumptions. A natural question therefore arises: What happens to the security of the above reduction when computationally secure commitments are used instead of perfect ones?<br /> <br />In this paper, we address the security of 1-2 QOT when computationally binding string commitments are available. In particular, we analyse the security of a primitive called <em>Quantum Measurement Commitment</em> when it is constructed from unconditionally concealing but computationally binding commitments. As measuring a quantum state induces an irreversible collapse, we describe a QMC as an instance of ``computational collapse of a quantum state''. In a QMC a state appears to be collapsed to a polynomial time observer who cannot extract full information about the state without breaking a computational assumption.<br /> <br />We reduce the security of QMC to a <em>weak</em> binding criteria for the string commitment. We also show that <em>secure</em> QMCs implies QOT using a straightforward variant of the reduction above.

scholarly journals Adaptive quantum state tomography with neural networks

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yihui Quek ◽  
Stanislav Fort ◽  
Hui Khoon Ng
Keyword(s):  
Machine Learning ◽  
Quantum State ◽  
The State ◽  
Learning To Learn ◽  
Seamless Integration ◽  
Quantum State Tomography ◽  
Flexible Machine ◽  
Meta Learning ◽  
Long Time ◽  
State Tomography

AbstractCurrent algorithms for quantum state tomography (QST) are costly both on the experimental front, requiring measurement of many copies of the state, and on the classical computational front, needing a long time to analyze the gathered data. Here, we introduce neural adaptive quantum state tomography (NAQT), a fast, flexible machine-learning-based algorithm for QST that adapts measurements and provides orders of magnitude faster processing while retaining state-of-the-art reconstruction accuracy. As in other adaptive QST schemes, measurement adaptation makes use of the information gathered from previous measured copies of the state to perform a targeted sensing of the next copy, maximizing the information gathered from that next copy. Our NAQT approach allows for a rapid and seamless integration of measurement adaptation and statistical inference, using a neural-network replacement of the standard Bayes’ update, to obtain the best estimate of the state. Our algorithm, which falls into the machine learning subfield of “meta-learning” (in effect “learning to learn” about quantum states), does not require any ansatz about the form of the state to be estimated. Despite this generality, it can be retrained within hours on a single laptop for a two-qubit situation, which suggests a feasible time-cost when extended to larger systems and potential speed-ups if provided with additional structure, such as a state ansatz.

scholarly journals Hayden-Preskill decoding from noisy Hawking radiation

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Ning Bao ◽  
Yuta Kikuchi
Keyword(s):  
Black Hole ◽  
Quantum State ◽  
Hawking Radiation ◽  
Thought Experiment ◽  
Natural Question ◽  
Early Radiation

Abstract In the Hayden-Preskill thought experiment, the Hawking radiation emitted before a quantum state is thrown into the black hole is used along with the radiation collected later for the purpose of decoding the quantum state. A natural question is how the recoverability is affected if the stored early radiation is damaged or subject to decoherence, and/or the decoding protocol is imperfectly performed. We study the recoverability in the thought experiment in the presence of decoherence or noise in the storage of early radiation.

scholarly journals Purification and redistribution of entanglement via single local filtering

2014 ◽  
Vol 12 (01) ◽  
pp. 1450004 ◽  
Author(s):  
K. O. Yashodamma ◽  
P. J. Geetha ◽  
Sudha
Keyword(s):  
Quantum State ◽  
The State ◽  
Quantum States ◽  
Local Action ◽  
Entanglement Transfer ◽  
Local Filtering

The effect of filtering operation with respect to purification and concentration of entanglement in quantum states are discussed in this paper. It is shown, through examples, that the local action of the filtering operator on a part of the composite quantum state allows for purification of the remaining part of the state. The redistribution of entanglement in the subsystems of a noise affected state is shown to be due to the action of local filtering on the non-decohering part of the system. The varying effects of the filtering parameter, on the entanglement transfer between the subsystems, depending on the choice of the initial quantum state is illustrated.

Security as a Whole-of-Government Project: Risk, Economy, Politics

2019 ◽  
pp. 236-268
Author(s):  
Andrew W. Neal
Keyword(s):  
Economic Growth ◽  
Black Box ◽  
The State ◽  
Project Risk ◽  
Political Rationality ◽  
Government Project ◽  
Work Security ◽  
A Site

This chapter departs from others by focusing on government as a site of politics. It finds the same trend at work: ‘security’ has been migrating out from a ‘black box’ at the dark heart of the state and into the wider reaches of government, encroaching on all policy areas and all government departments. Building on current literatures on risk, the chapter argues that central to this trend is the rise of a risk-based based rationality in government, which supplants the traditional threat-based security logic with one based on possibilities. The chapter argues that this allows ‘security’ to become subordinate to other political goals such as economic growth, relativising its traditional existential claim on political rationality.

Reframing Audience

2014 ◽  
pp. 148-164 ◽  
Author(s):  
G. R. Boynton ◽  
Glenn W. Richardson Jr.
Keyword(s):  
Political Discourse ◽  
Public Domain ◽  
Black Box ◽  
The State ◽  
Evaluative Judgment ◽  
Critical Importance ◽  
The Public ◽  
State Of The Union

Analysis of the audiences for the state of the union addresses on Twitter from 2010-2012 provides analytical leverage in unpacking the concept of audience, which has largely inhabited an analytical “black box,” seen as of critical importance but little understood. The authors frame audience as “co-motion” as it evolves from a broadcast medium to a medium of interaction in three moves: hashtags that establish a space for gathering, retweets that share reading, and sharing of urls that serve to communicate importance, evaluative judgment, and justification. They contrast the response of the congressional audience and the Twitter audience and find, while there was substantial overlap in their applause, members of Congress were less responsive than the Twitter audience to the president's calls for them to meet their responsibilities and less responsive to criticisms of major corporations. The authors find a vibrant political discourse on Twitter reaching a potential audience that rivals in size that of television, as audience becomes the public domain.

scholarly journals Fast Constructive Recognition of Black-Box Unitary Groups

2003 ◽  
Vol 6 ◽  
pp. 162-197 ◽  
Author(s):  
Peter A. Brooksbank
Keyword(s):  
Homomorphic Image ◽  
Polynomial Time ◽  
Unitary Group ◽  
Black Box ◽  
Unitary Groups ◽  
Discrete Logarithms ◽  
Cyclic Groups

AbstractIn this paper, the author presents a new algorithm to recognise, constructively, when a given black-box group is a homomorphic image of the unitary group SU(d, q) for known d and q. The algorithm runs in polynomial time, assuming the existence of oracles for handling SL(2, q) subgroups, and for computing discrete logarithms in cyclic groups of order q ± 1.

Primary state diffusion

1994 ◽  
Vol 447 (1929) ◽  
pp. 189-209 ◽  
Keyword(s):  
Quantum State ◽  
State Vector ◽  
Quantum Dynamics ◽  
Diffusion Theory ◽  
The State ◽  
Classical Dynamics ◽  
State Diffusion ◽  
Quantum State Diffusion ◽  
Spontaneous Localization ◽  
Ordinary Quantum

Primary quantum state diffusion (PSD) theory is an alternative quantum theory from which classical dynamics, quantum dynamics and localization dynamics are derived. It is based on four principles, that a system is represented by an operator, its state by a normalized state vector, the state vector satisfies a Langevin-Itô state diffusion equation, and the resultant density operator for an ensemble must satisfy an equation of elementary Lindblad form. There are three conditions. The ז 0 first determines the operator, to within an undetermined universal time constant ז 0 . The second and third conditions put opposing bounds on ז 0 . Dissipation of coherence is distinguished from destruction of coherence. The state diffusion destroys coherence and produces the localization or reduction that makes classical dynamics possible. PSD theory is a development of the environmental quantum state diffusion theory of Gisin and Percival and particularly resembles earlier proposals by Gisin and by Milburn. It is also related to the spontaneous localization theories of Ghirardi, Rimini and Weber, of Diósi and of Pearle. The non-relativistic PSD theory is of value only for systems which occupy small regions of space. Special relativity is needed for more extended systems even when they contain only slowly moving massive particles. Experiments on coherence lifetimes and matter interferometry are proposed which either measure ז 0 or put bounds on it, and which might distinguish between PSD and ordinary quantum mechanics.

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