59,321 research outputs found
An impossibility result for process discrimination
Two series of binary observations and are
presented: at each time we are given and . It is assumed
that the sequences are generated independently of each other by two
B-processes. We are interested in the question of whether the sequences
represent a typical realization of two different processes or of the same one.
We demonstrate that this is impossible to decide, in the sense that every
discrimination procedure is bound to err with non-negligible frequency when
presented with sequences from some B-processes. This contrasts earlier positive
results on B-processes, in particular those showing that there are consistent
-distance estimates for this class of processes
An impossibility result for process discrimination
International audienceTwo series of binary observations and are presented: at each time we are given and . It is assumed that the sequences are generated independently of each other by two B-processes. We are interested in the question of whether the sequences represent a typical realization of two different processes or of the same one. We demonstrate that this is impossible to decide, in the sense that every discrimination procedure is bound to err with non-negligible frequency when presented with sequences from some B-processes. This contrasts earlier positive results on B-processes, in particular those showing that there are consistent -distance estimates for this class of processes
Algorithmic Fairness from a Non-ideal Perspective
Inspired by recent breakthroughs in predictive modeling, practitioners in both industry and government have turned to machine learning with hopes of operationalizing predictions to drive automated decisions. Unfortunately, many social desiderata concerning consequential decisions, such as justice or fairness, have no natural formulation within a purely predictive framework. In efforts to mitigate these problems, researchers have proposed a variety of metrics for quantifying deviations from various statistical parities that we might expect to observe in a fair world and offered a variety of algorithms in attempts to satisfy subsets of these parities or to trade o the degree to which they are satised against utility. In this paper, we connect this approach to fair machine learning to the literature on ideal and non-ideal methodological approaches in political philosophy. The ideal approach requires positing the principles according to which a just world would operate. In the most straightforward application of ideal theory, one supports a proposed policy by arguing that it closes a discrepancy between the real and the perfectly just world. However, by failing to account for the mechanisms by which our non-ideal world arose, the responsibilities of various decision-makers, and the impacts of proposed policies, naive applications of ideal thinking can lead to misguided interventions. In this paper, we demonstrate a connection between the fair machine learning literature and the ideal approach in political philosophy, and argue that the increasingly apparent shortcomings of proposed fair machine learning algorithms reflect broader troubles
faced by the ideal approach. We conclude with a critical discussion of the harms of misguided solutions, a
reinterpretation of impossibility results, and directions for future researc
Practical private database queries based on a quantum key distribution protocol
Private queries allow a user Alice to learn an element of a database held by
a provider Bob without revealing which element she was interested in, while
limiting her information about the other elements. We propose to implement
private queries based on a quantum key distribution protocol, with changes only
in the classical post-processing of the key. This approach makes our scheme
both easy to implement and loss-tolerant. While unconditionally secure private
queries are known to be impossible, we argue that an interesting degree of
security can be achieved, relying on fundamental physical principles instead of
unverifiable security assumptions in order to protect both user and database.
We think that there is scope for such practical private queries to become
another remarkable application of quantum information in the footsteps of
quantum key distribution.Comment: 7 pages, 2 figures, new and improved version, clarified claims,
expanded security discussio
A short impossibility proof of Quantum Bit Commitment
Bit commitment protocols, whose security is based on the laws of quantum
mechanics alone, are generally held to be impossible on the basis of a
concealment-bindingness tradeoff. A strengthened and explicit impossibility
proof has been given in: G. M. D'Ariano, D. Kretschmann, D. Schlingemann, and
R. F. Werner, Phys. Rev. A 76, 032328 (2007), in the Heisenberg picture and in
a C*-algebraic framework, considering all conceivable protocols in which both
classical and quantum information are exchanged. In the present paper we
provide a new impossibility proof in the Schrodinger picture, greatly
simplifying the classification of protocols and strategies using the
mathematical formulation in terms of quantum combs, with each single-party
strategy represented by a conditional comb. We prove that assuming a stronger
notion of concealment--worst-case over the classical information
histories--allows Alice's cheat to pass also the worst-case Bob's test. The
present approach allows us to restate the concealment-bindingness tradeoff in
terms of the continuity of dilations of probabilistic quantum combs with
respect to the comb-discriminability distance.Comment: 15 pages, revtex
Quantum State Separation, Unambiguous Discrimination and Exact Cloning
Unambiguous discrimination and exact cloning reduce the square-overlap
between quantum states, exemplifying the more general type of procedure we term
state separation. We obtain the maximum probability with which two equiprobable
quantum states can be separated by an arbitrary degree, and find that the
established bounds on the success probabilities for discrimination and cloning
are special cases of this general bound. The latter also gives the maximum
probability of successfully producing N exact copies of a quantum system whose
state is chosen secretly from a known pair, given M initial realisations of the
state, where N>M. We also discuss the relationship between this bound and that
on unambiguous state discrimination.Comment: RevTeX, 5 pages postscrip
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