# Transferring multiqubit entanglement onto memory qubits in a decoherence-free subspace

## TL;DR

This paper presents a method to transfer entangled multiqubit states onto memory qubits within a decoherence-free subspace, enhancing quantum information protection against dephasing without increasing operation time.

## Contribution

The work introduces a scalable, measurement-free protocol for transferring GHZ entangled states onto memory qubits in a decoherence-free subspace, applicable to various qubit types.

## Key findings

- Successful transfer of GHZ states onto memory qubits
- Protection of entanglement against collective dephasing
- Operation time independent of qubit number

## Abstract

Different from the previous works on generating entangled states, this work is focused on how to transfer the prepared entangled states onto memory qubits for protecting them against decoherence. We here consider a physical system consisting of $n$ operation qubits and $2n$ memory qubits placed in a cavity or coupled to a resonator. A method is presented for transferring $n$-qubit Greenberger-Horne-Zeilinger (GHZ) entangled states from the operation qubits (i.e., information processing cells) onto the memory qubits (i.e., information memory elements with long decoherence time). The transferred GHZ states are encoded in a decoherence-free subspace against collective dephasing, and thus can be immune from decoherence induced by a dephasing environment. In addition, the state transfer procedure has nothing to do with the number of qubits, the operation time does not increase with the number of qubits, and no measurement is needed for the state transfer. This proposal can be applied to a wide range of hybrid qubits such as natural atoms and artificial atoms (e.g., various solid-state qubits).