Timelike curves can increase entanglement with LOCC

Area of Science:

• Quantum Information Science
• Theoretical Physics
• Cosmology

Background:

• Entanglement is a fundamental quantum resource, typically conserved under local operations and classical communication (LOCC).
• Bell states are maximally entangled quantum states crucial for quantum information tasks.
• Closed timelike curves (CTCs) are theoretical paths in spacetime that return to their starting point.

Purpose of the Study:

• To investigate the impact of Deutschian closed timelike curves (D-CTCs) and open timelike curves (OTCs) on quantum entanglement.
• To determine if entanglement can be increased using LOCC in the presence of CTCs.
• To analyze Bell state discrimination protocols under CTCs.

Main Methods:

• Theoretical analysis of quantum entanglement dynamics.
• Application of Bell state discrimination protocols.
• Investigation of local operations and classical communication (LOCC) within CTC frameworks.

Main Results:

• The presence of D-CTCs and OTCs allows for the increase of entanglement via LOCC.
• This finding contradicts the standard understanding of entanglement conservation.
• Four Bell states can be unambiguously distinguished using LOCC with CTCs, a task previously considered impossible.

Conclusions:

• The existence of physical CTCs would necessitate a revision of fundamental principles of quantum entanglement.
• CTCs offer novel possibilities for manipulating and utilizing quantum entanglement.
• Bell state discrimination becomes feasible with CTCs, opening new avenues in quantum information processing.