Quantum Signaling to the Past Using P-CTCS

TL;DR

This paper explores how Postselected Closed Timelike Curves (P-CTCs) can be used to send non-orthogonal quantum states to the past, analyzing causality violations and proposing consistency conditions.

Contribution

It introduces a protocol for signaling four non-orthogonal states to the past using P-CTCs and discusses causality preservation mechanisms.

Findings

Successfully demonstrated signaling of four non-orthogonal states to the past.

Identified causality violations and proposed two consistency relations to prevent them.

Analyzed the implications of P-CTCs on causality and quantum communication.

Abstract

Closed Timelike Curves (CTCs) are intriguing relativistic objects that allow for time travel to the past and can be used as computational resources. In Deutschian Closed Timelike Curves (D-CTCs), due to the monogamy of entanglement, non-local correlations between entangled states are destroyed. In contrast, for Postselected Closed Timelike Curves (P-CTCs), a second variant of CTCs, the non-local correlations are preserved. P-CTCs can be harnessed for the signaling of non-orthogonal states to the past without a disruption of causality. In this paper, we take up signaling to the past and show a method of sending four non-orthogonal states to the past using P-CTCs. After constructing our signaling protocol, we study the causality violations that our protocol results in and put forward two consistency relations to prevent them.