Polarization entanglement purification of nonlocal microwave photons based on the cross-Kerr effect in circuit QED

TL;DR

This paper proposes a novel polarization entanglement purification protocol for nonlocal microwave photons using the cross-Kerr effect in circuit QED, enhancing the security and efficiency of microwave-based quantum communication.

Contribution

It introduces a new purification protocol utilizing polarization parity-check QND detectors based on cross-Kerr effects in circuit QED, addressing decoherence issues in quantum channels.

Findings

The protocol effectively improves entanglement purity under environmental noise.

Experimental parameters for implementing the QND measurement are provided.

The method is suitable for long-distance microwave quantum communication, including satellite links.

Abstract

Microwave photons have become very important qubits in quantum communication as the first quantum satellite has been launched successfully. Therefore, it is a necessary and meaningful task for ensuring the high security and efficiency of microwave-based quantum communication in practice. Here, we present an original polarization entanglement purification protocol for nonlocal microwave photons based on the cross-Kerr effect in circuit quantum electrodynamics (QED). Our protocol can solve the problem that the purity of maximally entangled states used for constructing quantum channels will decrease due to decoherence from environment noise. This task is accomplished by means of the polarization parity-check quantum nondemolition (QND) detector, the bit-flipping operation, and the linear microwave elements. The QND detector is composed of several cross-Kerr effect systems which can be realized by coupling two superconducting transmission line resonators to a superconducting molecule with the N-type level structure. We give the applicable experimental parameters of QND measurement system in circuit QED and analyze the fidelities. Our protocol has good applications in long-distance quantum communication assisted by microwave photons in the future, such as satellite quantum communication.