Comparison of quantum statistical models: equivalent conditions for sufficiency

A family of probability distributions (i.e. a statistical model) is said to be sufficient for another, if there exists a transition matrix transforming the probability distributions in the former to the probability distributions in the latter. The Blackwell-Sherman-Stein (BSS) theorem provides necessary and sufficient conditions for one statistical model to be sufficient for another, by comparing their information values in statistical decision problems. In this paper we extend the BSS theorem to quantum statistical decision theory, where statistical models are replaced by families of density matrices defined on finite-dimensional Hilbert spaces, and transition matrices are replaced by completely positive, trace-preserving maps (i.e. coarse-grainings). The framework we propose is suitable for unifying results that previously were independent, like the BSS theorem for classical statistical models and its analogue for pairs of bipartite quantum states, recently proved by Shmaya. An important role in this paper is played by statistical morphisms, namely, affine maps whose definition generalizes that of coarse-grainings given by Petz and induces a corresponding criterion for statistical sufficiency that is weaker, and hence easier to be characterized, than Petz's.Comment: v4: final version to appear on Communications in Mathematical Physics. v3: submitted version, further improvements and results added, still 23 pages. v2: presentation improved and new results added, now 23 pages. v1: 20 pages, article class, no figure

Shor's quantum algorithm using electrons in semiconductor nanostructures

Shor's factoring algorithm illustrates the potential power of quantum computation. Here we present and numerically investigate a proposal for a compiled version of such an algorithm based on a quantum-wire network exploiting the potentialities of fully coherent electron transport assisted by the surface acoustic waves. Specifically, a non standard approach is used to implement, in a simple form, the quantum circuits of the modular exponentiation execution for the simplest instance of the Shor's algorithm, that is the factorization of $N$=15. The numerical procedure is based on a time-dependent solution of the multi-particle Schr\"odinger equation. The near-ideal algorithm performance and the large estimated fidelity indicate the efficiency of the protocol implemented, which also results to be almost unsensitive to small destabilizing effects during quantum computation.Comment: 22 pages, 7 figure

Britain and the Bomb: Nuclear Diplomacy, 1964- 1970 (Book Review) by David James Gill

Review of Britain and the Bomb: Nuclear Diplomacy, 1964- 1970 by David James Gill

General theory of environment-assisted entanglement distillation

We evaluate the one-shot entanglement of assistance for an arbitrary bipartite state. This yields another interesting result, namely a characterization of the one-shot distillable entanglement of a bipartite pure state. This result is shown to be stronger than that obtained by specializing the one-shot hashing bound to pure states. Finally, we show how the one-shot result yields the operational interpretation of the asymptotic entanglement of assistance proved in [Smolin et al., Phys. Rev. A 72, 052317 (2005)].Comment: 23 pages, one column, final published versio

Comparison of Noisy Channels and Reverse Data-Processing Theorems

This paper considers the comparison of noisy channels from the viewpoint of statistical decision theory. Various orderings are discussed, all formalizing the idea that one channel is "better" than another for information transmission. The main result is an equivalence relation that is proved for classical channels, quantum channels with classical encoding, and quantum channels with quantum encoding.Comment: 5 two-column pages, 3 figures; presented at 2017 IEEE Information Theory Workshop, Kaohsiun

Mal-Adjusted: Integration of Selves in Joss Whedon\u27s \u3ci\u3eFirefly\u3c/i\u3e

Joss Whedon’s Firefly and Serenity offer a brand new take on the well established science fiction film genre, one that many authors and viewers believe needed Whedon’s fresh new ideas to prevent further stagnating of the genre. Whedon’s Firefly focuses on the lives of Malcolm Reynolds (Mal) and his crew aboard the Firefly-class space ship named Serenity. Mal is the most compelling of the characters on the show because he is, in a way, the most fragile one. In the series premiere, “Serenity,” Mal is a complete man, fighting as a volunteer in a civil war. After his army is abandoned in Serenity Valley by their commanders while the latter negotiate a peace treaty, something inside Mal breaks; he becomes a fractured man, losing his faith in God, in humanity and in government. Over the next six years, he buys the spaceship Serenity and gathers a close-knit crew in an attempt to put himself back together and to create a new identity for himself. Mal\u27s identity conflict speaks to Firefly\u27s viewers, and we are able to relate not only to Mal and his desire to protect himself and his pseudo-family, but also to his efforts to make himself whole by establishing a place for himself in the world. Mal’s search for self identification through the development of loyal relationships is what inspires viewers to connect to Mal, which contributes to their untiring devotion to the Firefly verse. By analyzing each of Firefly’s characters in relation to Mal, I examine how they contribute to his efforts to rebuild his identity through the construction of a combined family unit. I use close analysis of the episodes of Firefly and the film Serenity, as well as several essays and articles written about the series and film. I also take into account interviews by creator, Joss Whedon, and actor, Nathan Fillion, about the development of the character Mal and the series as a whole. Actor Nathan Fillion, who plays Mal, writes: “Looking at Kaylee, I could tell what kind of man Mal was. Speaking to Zoe, I could tell what kind of leader Mal was. Arguing with Wash and Jayne, I knew the limits of Mal’s patience. They made me Mal. Looking back, I know now that everyone in the cast was, in essence, his or her character” (Fillion 52). Viewers are able to identify with every character on Firefly because they are modeled after real people. Mal, and the rest of Serenity’s crew, are the kinds of people who don’t care how society defines them; they are the ones who strongly stand apart from the rest of society and give everyone else hope that they too can live their lives as fully realized individuals. Fans’ love for Firefly proves that there is a strong unit of viewers who rely on television not only to provide entertainment, but also to provide for them a set of inspiring, realistic characters who they can relate to