Fig. 2: Comparison of Encoding Strategies for 2-copy LUI States. | Nature Communications

Fig. 2: Comparison of Encoding Strategies for 2-copy LUI States.

From: Informationally complete distributed metrology without a shared reference frame

Fig. 2: Comparison of Encoding Strategies for 2-copy LUI States.The alternative text for this image may have been generated using AI.

a 2-LUI-IE Protocol: Both copies undergo the same encoding operation, Θθ, and in this case, only nonlocal interactions can give rise to a non-vanishing QFI. b 2-LUI-RE Protocol: The two copies are reversely encoded with Θθ and Θ−θ. This structure explicitly breaks the SWAP symmetry between the copies. Crucially, while Θθ is depicted as a global unitary for generality, this strategy is effective even when the encoding is generated by purely local interactions at a single site.

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