Adiabatic Fock state generation and faithful Wigner tomography in a Kerr nonlinear resonator

Fock states are the simplest and the most well-known nonclassical states of light. Despite its fundamental and practical importance, generation of Fock state is a challenging task because we do not have means to control the levels of a linear quantum oscillator selectively without an additional nonlinear system.

Here, we present implementation of adiabatic Fock state generation using Kerr nonlinearity. We adiabatically vary the detuning and the strength of the resonator driving field to let the state evolve from the vacuum state to the target Fock state [1].

The fidelity of our Fock state is obtained by Wigner tomography. For this we employ parity measurement and quantum state tomography with neural network algorithm, conditional generative adversarial network (QST-CGAN) [2]. The technical difficulty of this process is unwanted Kerr evolution during the parity measurement. We solve this problem by using ultrafast pulse control and post-processing. QST-CGAN constructs the density matrix from our parity measurement and finally gives us the state fidelity.

[1] R. Yanagimoto et al., Adiabatic Fock-state-generation scheme using Kerr nonlinearity, Phy. Rev. A 100, 033822 (2019)

[2] S. Ahmed et al., Quantum State Tomography with Conditional Generative Adversarial Networks, Phy. Rev. Lett. 127, 140502 (2021)