Standard classical and quantum description relies on a single world or copy. However, the philosophical problems with interpretation of measurement result in quantum mechanics lead to the option of many worlds so that each world can have a different history of measurement results, invented by Hugh Everett, Reviews of Modern Physics 29, 4541957 (1957). For a long time, they remained a purely abstract idea, unverfiable/falsifiable. An expection was a paper by Rainer Plaga, Foundations of Physics 27, 559 (1997) [see arxiv version ], who suggested that the worlds can communicate with eah other. Years later, I have proposed a modification, many copies, which are apparently noninteracting, but they interact strongly at the moment od macroscopic collapse, bringing all the worlds to the same state. Just like many Schrödinger cates, some dead, some alive, collapse to the state of all dead or all alive. Such interworld collapse and any interworld interaction in general can lead to experimental tests, where the system is probed (a) if it remains in the single world/copy state or (b) if it collapsed in a sequential measurements. These ideas have been published:
Objective realism and Joint Measurability in Quantum Many Copies
[PDF ] [Annalen der Physik 530, 1800002 (2018)] [arXiv:1805.12237]
However, recent progress in building quantum computers open a possibility to test them as an extra quantum space. Using IBM Quantum, we have found anomalies beyond 5 standard deviations in qubit rotations that can be a signature of many copies. The tests need further confirmation and exclusion of parasitic effects like leakage to excited states or neighboring qubits. These options seems unlikely, taking into account anharmonicity and frequency detuning between nearest qubits. Moreover, the anomalies occurrence cannot be predicted just from qubit parameters (errors, frequencies, etc.) and they depend much on daily calibrations. Therefore the case needs serious and urgent clarification.
Tomasz Białecki, Tomasz Rybotycki, Josep Batle, Adam Bednorz
Quantum dimension witness with a single repeated operation
[PDF ] [Physical Review A 109, L020201 (2024)] [2308.11246]
Tomasz Białecki, Tomasz Rybotycki, Jakub Tworzydło, Adam Bednorz
Testing the accuracy of qubit rotations on a public quantum computer
[PDF ] [Frontiers in Physics 12, 1360080 (2024) (open access)] [2112.07567 ]
Tomasz Białecki, Tomasz Rybotycki, Jakub Tworzydło, Josep, Batle, Adam Bednorz
Precise certification of a qubit space
[PDF ] [EPJ Quant. Technol. 11, 21 (2024) (open access)] [2301.03296]