The Experts below are selected from a list of 463122 Experts worldwide ranked by ideXlab platform
William K Wootters - One of the best experts on this subject based on the ideXlab platform.
-
real vector space Quantum Theory with a universal Quantum bit
Physical Review A, 2013Co-Authors: Antoniya A Aleksandrova, Victoria Borish, William K WoottersAbstract:We explore a model of the world based on real-vector-space Quantum Theory. In our model the familiar complex phase appearing in Quantum states is replaced by a single binary object that we call the ubit, which is not localized and which can interact with any object in the world. Ordinary complex-vector-space Quantum Theory can be recovered from this model if we simply impose a certain restriction on the sets of allowed measurements and transformations (Stueckelberg's rule), but in this paper we try to obtain the standard Theory, or a close approximation to it, without invoking such a restriction. We look particularly at the effective Theory that applies to a subsystem when the ubit is interacting with a much larger environment. In a certain limit it turns out that the ubit-environment interaction has the effect of enforcing Stueckelberg's rule automatically, and we obtain a one-parameter family of effective theories--modifications of standard Quantum Theory--that all satisfy this rule. The one parameter is the ratio s/omega, where s quantifies the strength of the ubit's interaction with the rest of the world and omega is the ubit's rotation rate. We find that when this parameter is small but not zero, the effective Theory is similar to standard Quantum Theory but is characterized by spontaneous decoherence of isolated systems.
-
limited holism and real vector space Quantum Theory
arXiv: Quantum Physics, 2010Co-Authors: Lucien Hardy, William K WoottersAbstract:Quantum Theory has the property of "local tomography": the state of any composite system can be reconstructed from the statistics of measurements on the individual components. In this respect the holism of Quantum Theory is limited. We consider in this paper a class of theories more holistic than Quantum Theory in that they are constrained only by "bilocal tomography": the state of any composite system is determined by the statistics of measurements on pairs of components. Under a few auxiliary assumptions, we derive certain general features of such theories. In particular, we show how the number of state parameters can depend on the number of perfectly distinguishable states. We also show that real-vector-space Quantum Theory, while not locally tomographic, is bilocally tomographic.
Howard Barnum - One of the best experts on this subject based on the ideXlab platform.
-
higher order interference and single system postulates characterizing Quantum Theory
New Journal of Physics, 2014Co-Authors: Markus Muller, Howard Barnum, Cozmin UdudecAbstract:We present a new characterization of Quantum Theory in terms of simple physical principles that is different from previous ones in two important respects: first, it only refers to properties of single systems without any assumptions on the composition of many systems; and second, it is closer to experiment by having absence of higher-order interference as a postulate, which is currently the subject of experimental investigation. We give three postulates?no higher-order interference, classical decomposability of states, and strong symmetry?and prove that the only non-classical operational probabilistic theories satisfying them are real, complex, and quaternionic Quantum Theory, together with three-level octonionic Quantum Theory and ball state spaces of arbitrary dimension. Then we show that adding observability of energy as a fourth postulate yields complex Quantum Theory as the unique solution, relating the emergence of the complex numbers to the possibility of Hamiltonian dynamics. We also show that there may be interesting non-Quantum theories satisfying only the first two of our postulates, which would allow for higher-order interference in experiments while still respecting the contextuality analogue of the local orthogonality principle.
-
higher order interference and single system postulates characterizing Quantum Theory
arXiv: Quantum Physics, 2014Co-Authors: Howard Barnum, Markus P Mueller, Cozmin UdudecAbstract:We present a new characterization of Quantum Theory in terms of simple physical principles that is different from previous ones in two important respects: first, it only refers to properties of single systems without any assumptions on the composition of many systems; and second, it is closer to experiment by having absence of higher-order interference as a postulate, which is currently the subject of experimental investigation. We give three postulates -- no higher-order interference, classical decomposability of states, and strong symmetry -- and prove that the only non-classical operational probabilistic theories satisfying them are real, complex, and quaternionic Quantum Theory, together with 3-level octonionic Quantum Theory and ball state spaces of arbitrary dimension. Then we show that adding observability of energy as a fourth postulate yields complex Quantum Theory as the unique solution, relating the emergence of the complex numbers to the possibility of Hamiltonian dynamics. We also show that there may be interesting non-Quantum theories satisfying only the first two of our postulates, which would allow for higher-order interference in experiments while still respecting the contextuality analogue of the local orthogonality principle.
Cozmin Ududec - One of the best experts on this subject based on the ideXlab platform.
-
higher order interference and single system postulates characterizing Quantum Theory
New Journal of Physics, 2014Co-Authors: Markus Muller, Howard Barnum, Cozmin UdudecAbstract:We present a new characterization of Quantum Theory in terms of simple physical principles that is different from previous ones in two important respects: first, it only refers to properties of single systems without any assumptions on the composition of many systems; and second, it is closer to experiment by having absence of higher-order interference as a postulate, which is currently the subject of experimental investigation. We give three postulates?no higher-order interference, classical decomposability of states, and strong symmetry?and prove that the only non-classical operational probabilistic theories satisfying them are real, complex, and quaternionic Quantum Theory, together with three-level octonionic Quantum Theory and ball state spaces of arbitrary dimension. Then we show that adding observability of energy as a fourth postulate yields complex Quantum Theory as the unique solution, relating the emergence of the complex numbers to the possibility of Hamiltonian dynamics. We also show that there may be interesting non-Quantum theories satisfying only the first two of our postulates, which would allow for higher-order interference in experiments while still respecting the contextuality analogue of the local orthogonality principle.
-
higher order interference and single system postulates characterizing Quantum Theory
arXiv: Quantum Physics, 2014Co-Authors: Howard Barnum, Markus P Mueller, Cozmin UdudecAbstract:We present a new characterization of Quantum Theory in terms of simple physical principles that is different from previous ones in two important respects: first, it only refers to properties of single systems without any assumptions on the composition of many systems; and second, it is closer to experiment by having absence of higher-order interference as a postulate, which is currently the subject of experimental investigation. We give three postulates -- no higher-order interference, classical decomposability of states, and strong symmetry -- and prove that the only non-classical operational probabilistic theories satisfying them are real, complex, and quaternionic Quantum Theory, together with 3-level octonionic Quantum Theory and ball state spaces of arbitrary dimension. Then we show that adding observability of energy as a fourth postulate yields complex Quantum Theory as the unique solution, relating the emergence of the complex numbers to the possibility of Hamiltonian dynamics. We also show that there may be interesting non-Quantum theories satisfying only the first two of our postulates, which would allow for higher-order interference in experiments while still respecting the contextuality analogue of the local orthogonality principle.
Adrian Kent - One of the best experts on this subject based on the ideXlab platform.
-
testing causal Quantum Theory
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2018Co-Authors: Adrian KentAbstract:Causal Quantum Theory assumes that measurements or collapses are well-defined physical processes, localized in spacetime, and never give perfectly reliable outcomes and that the outcome of one meas...
-
testing causal Quantum Theory
arXiv: Quantum Physics, 2018Co-Authors: Adrian KentAbstract:Causal Quantum Theory assumes that measurements or collapses are well-defined physical processes, localised in space-time, and never give perfectly reliable outcomes and that the outcome of one measurement only influences the outcomes of others within its future light cone. Although the Theory has unusual properties, it is not immediately evident that it is inconsistent with experiment to date. I discuss its implications and experimental tests.
-
causal Quantum Theory and the collapse locality loophole
Physical Review A, 2005Co-Authors: Adrian KentAbstract:Causal Quantum Theory is an umbrella term for ordinary Quantum Theory modified by two hypotheses: state vector reduction is a well-defined process, and strict local causality applies. The first of these holds in some versions of Copenhagen Quantum Theory and need not necessarily imply practically testable deviations from ordinary Quantum Theory. The second implies that measurement events which are spacelike separated have no nonlocal correlations. To test this prediction, which sharply differs from standard Quantum Theory, requires a precise definition of state vector reduction. Formally speaking, any precise version of causal Quantum Theory defines a local hidden variable Theory. However, causal Quantum Theory is most naturally seen as a variant of standard Quantum Theory. For that reason it seems a more serious rival to standard Quantum Theory than local hidden variable models relying on the locality or detector efficiency loopholes. Some plausible versions of causal Quantum Theory are not refuted by any Bell experiments to date, nor is it evident that they are inconsistent with other experiments. They evade refutation via a neglected loophole in Bell experiments---the collapse locality loophole---which exists because of the possible time lag between a particle entering a measurement device and a collapse taking place. Fairly definitive tests of causal versus standard Quantum Theory could be made by observing entangled particles separated by $\ensuremath{\approx}0.1$ light seconds.
Antoniya A Aleksandrova - One of the best experts on this subject based on the ideXlab platform.
-
real vector space Quantum Theory with a universal Quantum bit
Physical Review A, 2013Co-Authors: Antoniya A Aleksandrova, Victoria Borish, William K WoottersAbstract:We explore a model of the world based on real-vector-space Quantum Theory. In our model the familiar complex phase appearing in Quantum states is replaced by a single binary object that we call the ubit, which is not localized and which can interact with any object in the world. Ordinary complex-vector-space Quantum Theory can be recovered from this model if we simply impose a certain restriction on the sets of allowed measurements and transformations (Stueckelberg's rule), but in this paper we try to obtain the standard Theory, or a close approximation to it, without invoking such a restriction. We look particularly at the effective Theory that applies to a subsystem when the ubit is interacting with a much larger environment. In a certain limit it turns out that the ubit-environment interaction has the effect of enforcing Stueckelberg's rule automatically, and we obtain a one-parameter family of effective theories--modifications of standard Quantum Theory--that all satisfy this rule. The one parameter is the ratio s/omega, where s quantifies the strength of the ubit's interaction with the rest of the world and omega is the ubit's rotation rate. We find that when this parameter is small but not zero, the effective Theory is similar to standard Quantum Theory but is characterized by spontaneous decoherence of isolated systems.