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Operational Quantum Reference Frame Transformations

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arxiv 2303.14002 v4 pith:EGQTPCGT submitted 2023-03-24 quant-ph math-phmath.MP

classification quant-phmath-phmath.MP
keywords framequantumreferenceobservablesrelativeframesstatestransformations
verification ladder T0 review T1 audit T2 compute T3 formal
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Quantum reference frames are needed in quantum theory for much the same reasons that reference frames are in classical theories: to manifest invariance in line with fundamental relativity principles and to provide a basis for the definition of observable quantities. Though around since the 1960s, and used in a wide range of applications, only recently has the means for transforming descriptions between different quantum reference frames been tackled in detail. In this work, we provide a general, operationally motivated framework for quantum reference frames and their transformations, holding for locally compact groups. The work is built around the notion of operational equivalence, in which quantum states that cannot be physically distinguished are identified. For example, we describe the collection of relative observables as a subspace of the algebra of invariants on the composite of system and frame, and from here the set of relative states is constructed through the identification of states which cannot be distinguished by relative observables. Through the notion of framed observables -- the formation of joint observables of system and frame -- of which the relative observables can be understood as examples, quantum reference frame transformations are then maps between equivalence classes of relative states which respect the framing. We give an explicit realisation in the setting that the initial frame admits a highly localized state with respect to the frame observable. The transformations are invertible exactly when the final frame also has such a localizability property. The procedure we present is in operational agreement with other recent inequivalent constructions on the domain of common applicability, but extends them in a number of ways, and weakens claims of entanglement generation through frame changes.

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Cited by 8 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Relational path integral, effective actions and quantum frame covariance in gravity

    hep-th 2026-07 conditional novelty 7.0 of 10

    The gravitational path integral is reformulated with dynamical reference frames, producing gauge-invariant correlators, frame-dependent vacua, and effective actions, with sharpness of events becoming frame-relative.

  2. How many degrees of freedom describe a quantum N-particle state?

    quant-ph 2026-07 conditional novelty 7.0 of 10

    For closed quantum N-particle systems all 3N canonical degrees of freedom are physical; the frame degrees of freedom that relational models discard reappear as non-Heisenberg terms in generalised uncertainty relations...

  3. Semi-local observables, edge modes and quantum reference frames in quantum electromagnetism: an algebraic approach

    math-ph 2025-08 conditional novelty 7.0 of 10

    Electromagnetic edge modes on bounded spacetimes with corners are treated as quantum reference frames for large gauge transformations via a state-independent C*-algebraic relativisation map, with superselection sector...

  4. Relational entanglement entropies and quantum reference frames in gauge theories

    hep-th 2025-06 accept novelty 7.0 of 10

    Quantum reference frames built from Wilson lines give lattice gauge theories gauge-invariant subsystem factorizations and a hierarchy of relational entanglement entropies.

  5. Partitions in quantum theory

    quant-ph 2025-06 conditional novelty 7.0 of 10

    A definition of multipartitions of quantum systems into possibly non-factor sub-C* algebras, with a representation theorem showing that some partitions, such as fermionic modes, are not fully representable on tensor-p...

  6. On the relation between perspective-neutral, algebraic, and effective quantum reference frames

    quant-ph 2025-07 conditional novelty 6.0 of 10

    For ideal quantum reference frames with a single constraint, the perspective-neutral, algebraic, and effective semiclassical approaches describe the same physics and the same frame-switching rules.

  7. Specifying the operational meaning of quantum reference frames

    quant-ph 2026-07 conditional novelty 5.0 of 10

    Position-superposed labs define quantum reference frames operationally, differ from Wigner's-friend observers, and can broadcast outcomes without decohering their position superposition.

  8. What can we do in a symmetry-constrained perspective? The importance of the total charge's status in quantum reference frame frameworks

    quant-ph 2025-10 conditional novelty 5.0 of 10

    A two-observer Z2 toy model is used to argue that internal observers can access the total charge, favoring weak over strong symmetry in quantum reference frame frameworks.

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