No-cloning theorem for 2WQC and postselection

TL;DR

This paper extends the no-cloning theorem proof to two-way quantum computing (2WQC) with postselection, demonstrating that the theorem remains valid despite the added conjugated state preparation operations.

Contribution

The paper provides a rigorous proof that the no-cloning theorem holds for 2WQC with postselection, addressing concerns about potential violations in extended quantum computational models.

Findings

No-cloning theorem remains valid for 2WQC with postselection.

Extension does not enable cloning attacks on quantum cryptographic protocols.

Supports security assumptions in advanced quantum computing models.

Abstract

Two-way quantum computers (2WQC) are proposed extension of standard 1WQC: adding conjugated state preparation operation $\langle 0|$ similar to postselection $|0\ra \langle 0|$, by performing a process which from perspective of CPT symmetry is the original state preparation process, for example by reversing EM impulses used for state preparation. As there were concerns that this extension might violate no-cloning theorem for example for attacks on quantum cryptographic protocols like BB84, here we extend the original proof to show this theorem still holds for 2WQC and postselection.