Quantum state tomography on closed timelike curves using weak measurements
2025 (English)In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 42, no 4, article id 045018Article in journal (Refereed) Published
Abstract [en]
Any given prescription of quantum time travel necessarily endows a Hilbert space to the chronology-violating (CV) system on the closed timelike curve (CTC). However, under the two foremost models, Deutsch's prescription (D-CTCs) and postselected teleportation (P-CTCs), the CV system is treated very differently: D-CTCs assign a definite form to the state on this system, while P-CTCs do not. To further explore this distinction, we present a methodology by which an operational notion of state may be assigned to their respective CV systems. This is accomplished via a conjunction of state tomography and weak measurements, with the latter being essential in leaving any notions of self-consistency intact. With this technique, we are able to verify the predictions of D-CTCs and, perhaps more significantly, operationally assign a state to the system on the P-CTC. We show that, for any given combination of chronology-respecting input and unitary interaction, it is always possible to recover the unique state on the P-CTC, and we provide a few specific examples in the context of select archetypal temporal paradoxes. We also demonstrate how this state may be derived from analysis of the P-CTC prescription itself, and we explore how it compares to its counterpart in the CV state predicted by D-CTCs.
Place, publisher, year, edition, pages
IOP Publishing , 2025. Vol. 42, no 4, article id 045018
Keywords [en]
quantum state tomography, closed timelike curves, weak measurements, temporal paradox, quantum mechanics, time travel
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-360047DOI: 10.1088/1361-6382/ada90bISI: 001414123200001Scopus ID: 2-s2.0-85219656924OAI: oai:DiVA.org:kth-360047DiVA, id: diva2:1938193
Note
QC 20250226
2025-02-172025-02-172025-03-12Bibliographically approved