Engineering a Kerr-based Deterministic Cubic Phase Gate via Gaussian Operations

TL;DR

This paper presents a deterministic method to implement a cubic phase gate in continuous-variable quantum computing using Gaussian operations and Kerr nonlinearity, achieving high fidelity with low loss.

Contribution

It introduces a measurement-free scheme combining displacement, squeezing, and Kerr effects to realize a cubic phase gate with reduced error and high fidelity.

Findings

Cubic phase gate error decreases inverse-quartically with squeezing.

High-fidelity cubic phase state generation is feasible with low linear loss.

The approach is compatible with all-optical platforms like quantum solitons.

Abstract

We propose a deterministic, measurement-free implementation of a cubic phase gate for continuous-variable quantum information processing. In our scheme, the applications of displacement and squeezing operations allow us to engineer the effective evolution of the quantum state propagating through an optical Kerr nonlinearity. Under appropriate conditions, we show that the input state evolves according to a cubic phase Hamiltonian, and we find that the cubic phase gate error decreases inverse-quartically with the amount of quadrature squeezing, even in the presence of linear loss. We also show how our scheme can be adapted to deterministically generate a nonclassical approximate cubic phase state with high fidelity using a ratio of native nonlinearity to linear loss of only $10^{-4}$, indicating that our approach may be experimentally viable in the near term even on all-optical platforms, e.g., using quantum solitons in pulsed nonlinear nanophotonics.