Quantum Mechanics is About Quantum Information

Joseph M. Landsberg

Vlatko Vedral

Abstract Quantum mechanics is a more accurate description of the microscopic world than classical mechanics, and quantum information, which is governed by the laws of quantum mechanics, is a more accurate description of information theory. The quantum laws of physics are fundamentally different from the classical laws and so, therefore, is the resulting information processing. In one limit, quantum information reduces to classical information; otherwise, quantum information is a much more general concept that allows information-processing protocols that have no classical analogue whatsoever. This chapter discusses the basics of quantum information, some differences between bits and qubits, quantum cryptography, trace and partial-trace operations, extension of Hilbert spaces, Schmidt decomposition, generalised measurements, CP-maps and positive operator-valued measurements, and the postulates of quantum mechanics.

Amit Hagar

Recent suggestions to supply quantum mechanics (QM) with realistic foundations by reformulating it in light of quantum information theory (QIT) are examined and are found wanting by pointing to a basic conceptual problem that QIT itself ignores, namely, the measurement problem. Since one cannot ignore the measurement problem and at the same time pretend to be a realist, as they stand, the suggestions to reformulate QM in light of QIT are nothing but instrumentalism in disguise.

Gregg S. Jaeger

Xian Ma

Quantum information is promising in solving certain computational problems and information \nsecurity. The power of its speed up and privacy is based on one of the most \ntested physical theory: quantum mechanics. Many of the promises of quantum information \nhas already been demonstrated in different implementations, which could also be viewed \nas witness of quantum mechanics. As we progress further in quantum information, we find \nthat some of the aspects of quantum mechanics could be tested in a novel way. Performing \nthose tests may lead to new physical theory or at least reinforce our belief of the accuracy \nof quantum mechanics. In this thesis, I report a few different approaches in testing the \nfoundation of quantum mechanics using results obtained from quantum optics. While developing \nsuch test, quantum state tomography is heavily used to characterize our system. \nI also report a simplified way of performing quantum state tomography for quantum state \nthat is close to pure state.