Knight Capital Group, Inc.

About: Knight Capital Group, Inc. is a based out in . It is known for research contribution in the topics: Approximation algorithm & Quantum information. The organization has 10 authors who have published 22 publications receiving 773 citations.

Classical command of quantum systems

Abstract: Quantum computation and cryptography both involve scenarios in which a user interacts with an imperfectly modelled or ‘untrusted’ system. It is therefore of fundamental and practical interest to devise tests that reveal whether the system is behaving as instructed. In 1969, Clauser, Horne, Shimony and Holt proposed an experimental test that can be passed by a quantum-mechanical system but not by a system restricted to classical physics. Here we extend this test to enable the characterization of a large quantum system. We describe a scheme that can be used to determine the initial state and to classically command the system to evolve according to desired dynamics. The bipartite system is treated as two black boxes, with no assumptions about their inner workings except that they obey quantum physics. The scheme works even if the system is explicitly designed to undermine it; any misbehaviour is detected. Among its applications, our scheme makes it possible to test whether a claimed quantum computer is truly quantum. It also advances towards a goal of quantum cryptography: namely, the use of ‘untrusted’ devices to establish a shared random key, with security based on the validity of quantum physics. A scheme is described that enables characterization and classical command of large quantum systems; it provides a test of whether a claimed quantum computer is truly quantum, and also advances towards a goal of quantum cryptography, namely the use of untrusted devices to establish a shared random key, with security based on the validity of quantum physics. Experimental interactions with quantum systems are necessarily limited, so is it possible to control and command such systems? Ben Reichardt et al. address this basic philosophical question about quantum mechanics with reference to quantum computation and cryptography, which involve imperfectly modelled or 'untrusted' systems. The authors describe a scheme that enables characterization of large quantum systems, providing a test of whether a claimed quantum computer is truly quantum. The results imply that it is possible to command an untrusted quantum system using classical interventions.

IBM streams processing language: analyzing big data in motion

Abstract: The IBM Streams Processing Language (SPL) is the programming language for IBM InfoSphere® Streams, a platform for analyzing Big Data in motion. By "Big Data in motion," we mean continuous data streams at high data-transfer rates. InfoSphere Streams processes such data with both high throughput and short response times. To meet these performance demands, it deploys each application on a cluster of commodity servers. SPL abstracts away the complexity of the distributed system, instead exposing a simple graph-of-operators view to the user. SPL has several innovations relative to prior streaming languages. For performance and code reuse, SPL provides a code-generation interface to C++ and Java®. To facilitate writing well-structured and concise applications, SPL provides higher-order composite operators that modularize stream sub-graphs. Finally, to enable static checking while exposing optimization opportunities, SPL provides a strong type system and user-defined operator models. This paper provides a language overview, describes the implementation including optimizations such as fusion, and explains the rationale behind the language design.

A classical leash for a quantum system: command of quantum systems via rigidity of CHSH games

Abstract: Can a classical experimentalist command an untrusted quantum system to realize arbitrary quantum dynamics, aborting if it misbehaves? If so, then we could realize the dream of device-independent quantum cryptography: using untrusted quantum devices to establish a shared random key, with security based on the correctness of quantum mechanics. It would also allow for testing whether a claimed quantum computer is truly quantum. We prove a rigidity theorem for the famous Clauser-Horne-Shimony-Holt (CHSH) game, first formulated to provide a means of experimentally testing the violation of the Bell inequalities. The theorem shows that the only way for the two non-communicating quantum players to win many games played in sequence is if their shared quantum state is close to the tensor product of EPR states (Bell states) and their measurements are the optimal CHSH measurements on successive qubits. This theorem may be viewed as analogous to classical multi-linearity testing, in the sense that the outcome of local checks gives a characterization of a global object.The rigidity theorem provides the basis of a technique by which a classical system can certify the joint, entangled state of a bipartite quantum system, as well as command the application of specific operators on each subsystem. This leads directly to a scheme for device-independent quantum key distribution. Control over the state and operators can also be leveraged to create more elaborate protocols for realizing general quantum circuits. In particular, it allows us to establish that a quantum interactive proof system with a classical verifier is as powerful as one with a quantum verifier, or QMIP = MIP*.

A distributed algorithm for large-scale generalized matching

Abstract: Generalized matching problems arise in a number of applications, including computational advertising, recommender systems, and trade markets. Consider, for example, the problem of recommending multimedia items (e.g., DVDs) to users such that (1) users are recommended items that they are likely to be interested in, (2) every user gets neither too few nor too many recommendations, and (3) only items available in stock are recommended to users. State-of-the-art matching algorithms fail at coping with large real-world instances, which may involve millions of users and items. We propose the first distributed algorithm for computing near-optimal solutions to large-scale generalized matching problems like the one above. Our algorithm is designed to run on a small cluster of commodity nodes (or in a MapReduce environment), has strong approximation guarantees, and requires only a poly-logarithmic number of passes over the input. In particular, we propose a novel distributed algorithm to approximately solve mixed packing-covering linear programs, which include but are not limited to generalized matching problems. Experiments on real-world and synthetic data suggest that a practical variant of our algorithm scales to very large problem sizes and can be orders of magnitude faster than alternative approaches.

Apache Airavata: Design and Directions of a Science Gateway Framework

Abstract: This paper provides an overview of the Apache Airavata software system for science gateways. Gateways use Airavata to manage application and workflow executions on a range of backend resources (grids, computing clouds, and local clusters). Airavata's design goal is to provide component abstractions for major tasks required to provide gateway application management. Components are not directly accessed but are instead exposed through a client Application Programming Interface. This design allows gateway developers to take full advantage of Airavata's capabilities, and Airavata developers (including those interested in middleware research) to modify Airavata's implementations and behavior. This is particularly important as Airavata evolves to become a scalable, elastic "platform as a service" for science gateways. We illustrate the capabilities of Airavata through the discussion of usage vignettes. As an Apache Software Foundation project, Airavata's open community governance model is as important as its software base. We discuss how this works within Airavata and how it may be applicable to other distributed computing infrastructure and cyber infrastructure efforts.