Quantum State Transfer Between Valley and Photon Qubits
Ming-Jay Yang1*, Yu-Shu Wu1, Han-Ying Peng2, Neil Na3
1Institute of Electronics Engineering, National Tsing Hua University, Hsinchu city, Taiwan
2Department of Physics, National Tsing Hua University, Hsinchu city, Taiwan
3Artilux Inc., Zhubei city, Hsinchu, Taiwan
* presenting author:MingJay Yang, email:mingjayyoung@gmail.com
Quantum state transfer (QST) between different types of qubits, namely, valley and photon qubit, is presented here for the application of long distance quantum communication. This QST is analogous to spin-photon QST [1-3], and is based on the electron-photon interaction in 2D hexagonal materials that obeys a unique optical transition selection rule, namely, the “electron valley – photon polarization” correspondence [4]. Such correspondence can be utilized to entangle electron valleys and circular polarizations of photons and attain the transfer of quantum states between valley and photon qubits [5]. A generic setup involving two optical cavities is introduced for the QST. The QST starts by sending an information-encoded photon into the first cavity to interact, entangle, and hence share the information with the valley qubit that has been initialized and placed in the cavity. It is then followed by the exit of a photon from the second cavity and a projection measurement performed on the polarization of the outgoing photon to un-entangle the valley and photon qubits and thus complete the transfer of information to the valley qubit. Such setup utilizes optical cavities to enhance the electron-photon interaction as well as facilitate both the entanglement and un-entanglement between valleys and polarizations required in the transfer. A quantum-mechanical wave equation-based analysis is performed, and analytical expressions are derived for the two important figures of merits that characterize the transfer, namely, yield and fidelity. Their dependencies on various qubit and cavity parameters will be discussed for optimization of the two figures.

In conclusion, the study suggests that the unique valley-polarization correspondence in 2D hexagonal materials can indeed be exploited to achieve valley-photon QST with promising yield and high fidelity. Such characteristics allow valley qubits to serve as quantum memories for long distance optical quantum communications as a scalable solution.

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Keywords: QST, valley qubits, quantum communication, fidelity, yield