Qubits are fundamental units for quantum computation. Photonics is a promising physical medium to realize large-scale quantum computation. One proposal to realize photonic qubits was proposed by Gottesman, Kitaev and Preskill (GKP). Here, the logical qubit is encoded into states of a bosonic mode or a quantum harmonic oscillator. It is expected that such a procedure will lead to a better quality and number of qubits.