Reference frame (quantum information)
The notion that certain quantum quantities — phase, angular position, spin direction — are only operationally meaningful relative to a physical system that instantiates a frame, not relative to an abstract external standard; traced to Aharonov & Susskind's 1967 work on the charge superselection rule and Aharonov & Kaufherr's 1984 "Quantum frames of reference," and surveyed in Bartlett, Rudolph & Spekkens's widely-cited 2007 Reviews of Modern Physics review.
In the vault it enters as the load-bearing move in Collins & Popescu's 2025 proposal for restoring individual-outcome conservation: they identify the reference frame for a conserved quantity with a physical "preparer" system, arguing a superposition of eigenstates must have been prepared relative to one. Okon, Sudarsky & Wiedemann (2026) reject this identification, arguing that a quantity's being frame-relative does not establish that the frame must be an additional material system, and that granting the inference anyway produces an infinite regress of reference systems.
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