Remote Implementation of Hidden or Partially Unknown Quantum Operators using Optimal Resources: A Generalized View

TL;DR

This paper introduces efficient protocols for remotely implementing specific quantum operators using minimal entanglement resources, analyzing their robustness and generalizations to complex controlled scenarios.

Contribution

It presents novel, resource-efficient protocols for remote quantum operator implementation, extending to controlled and bidirectional cases with minimal entanglement.

Findings

Protocols use optimal two-qubit entangled states.

Photon loss impact is analyzed for both schemes.

Protocols are generalized to controlled and bidirectional versions.

Abstract

Two protocols are proposed for two closely linked but different variants of remote implementation of quantum operators of specific forms. The first protocol is designed for the remote implementation of the single qubit hidden quantum operator, whereas the second one is designed for the remote implementation of the partially unknown single qubit quantum operator. In both cases two-qubit maximally entangled state, which is entangled in the spatial degree of freedom is used. The quantum resources used here are optimal and easy to realize and maintain in comparison to the multi-partite or multi-mode entangled states used in earlier works. The impact of photon loss due to interaction with the environment is analyzed for both the schemes. The proposed protocols are also generalized to their controlled, bidirectional, cyclic, controlled cyclic, and controlled bidirectional versions and it is shown that either Bell state alone or products of Bell states will be sufficient to perform these tasks with some additional classical communications in the controlled cases only. This is in sharp contrast to the earlier proposals that require large entangled states. In addition, it's noted that remote implementation of hidden or partially unknown operators involving multiple controllers and/or multiple players who jointly apply the desired operator(s) would require quantum channels more complex than the Bell states and their products. Explicit forms of such quantum channels are also provided.