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Chris Fields

Publications and source records attributed to Chris Fields.

43 records · Page 3Linked to original sources
arXiv2011

Information contents and architectural requirements of observer "ready" states

A functional analysis of the task of observing multiple macroscopic quantum systems over an extended period of time and then reporting the accumulated results is used to investigate the information that must be encoded in the "ready" state |O^r> of any finite, macroscopic observer O capable of performing this task. Decoherence considerations show that this task can be considered as involving local observations under classical conditions (LOCC), allowing the use of classical automata theory to define a minimal observer. It is shown that such a minimal observer must implement a functional architecture equivalent to a classical Turing machine and must encode in |O^r> a classical specification of the complete set of reportable apparatus states. The observation task is then re-characterized employing an explicit model of such a minimal observer, and it is shown that both the assumption that external systems have well-defined boundaries against the environment and the assumption of decoherence are unnecessary for the characterization of measurements made by a minimal observer. It is shown that the observables available to a minimal observer are positive operator-valued measures (POVMs) and that the measurement results reported by a minimal observer comply with the Born rule. The differences in underlying physical assumptions between this "systems-free" treatment of observation and that traditionally employed in analyses of quantum measurement and quantum communication are discussed.

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arXiv2011

Quantum mechanics from five physical assumptions

Five physical assumptions are proposed that together entail the general qualitative results, including the Born rule, of non-relativistic quantum mechanics by physical and information-theoretic reasoning alone. Two of these assumptions concern fundamental symmetries of physical interactions. The third concerns the Hilbert-space dimensions and the fourth and fifth the self-interaction Hamiltonians of the systems that function as "observers" within the theory. These assumptions are shown to provide a sufficient motivation for the usual Hilbert-space formalism, and to obviate the observation-related axioms and most interpretative assumptions with which minimal quantum mechanics is typically supplemented.

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arXiv2010

Quantum Darwinism requires an extra-theoretical assumption of encoding redundancy

Observers restricted to the observation of pointer states of apparatus cannot conclusively demonstrate that the pointer of an apparatus A registers the state of a system of interest S without perturbing S. Observers cannot, therefore, conclusively demonstrate that the states of a system S are redundantly encoded by pointer states of multiple independent apparatus without destroying the redundancy of encoding. The redundancy of encoding required by quantum Darwinism must, therefore, be assumed from outside the quantum-mechanical formalism and without the possibility of experimental demonstration.

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arXiv2010

Computational costs of data definition at the quantum - classical interface

Model-independent semantic requirements for user specification and interpretation of data before and after quantum computations are characterized. Classical computational costs of assigning classical data values to quantum registers and to run-time parameters passed across a classical-to-quantum application programming interface are derived. It is shown that the classical computational costs of data definition equal or exceed the classical computational cost of solving the problem of interest for all applications of quantum computing except computations defined over the integers and the simulation of linear systems with linear boundary conditions.

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arXiv2010

Decompositional equivalence

Both classical and quantum mechanics assume that physical laws are invariant under changes in the way that the world is labeled. This Principle of Decompositional Equivalence is formalized, and shown to forbid finite experimental demonstrations that given pointer states |p1> and |p2> refer to the same physical system S. It is then shown that any extra-theoretical assumption that given pointer states |p1> and |p2> with indistinguishable coefficients in a Schmidt basis for the universe refer to the same physical system S is stronger than the assumption of classicality. Standard interpretations of quantum mechanics make such as assumption in analyzing measurement; hence they are logically inconsistent.

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arXiv2009

Three consequences of decompositional consistency

Decompositions of the world into systems have typically been regarded as arbitrary extra-theoretical assumptions in discussions of quantum measurement. One can instead regard decompositions as part of the theory, and ask what conditions they must satisfy for self-consistency. It is shown that self-consistent decompositions that specify a measurement context (i.e. von Neumann decompositions) must represent apparatus as containing internal decohering environments and as having known pointer components and ready states. Under these circumstances a von Neumann decomposition can function as a component of the ready state of the observer. Minimal no-collapse quantum mechanics supplemented by these consistency requirements on von Neumann decompositions avoids the measurement problem.

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