Measurement-Induced Strong Kerr Nonlinearity for Weak Quantum States of Light

Abstract

Strong nonlinearity at the single photon level represents a crucial enabling tool for optical quantum technologies. Here we report on experimental implementation of a strong Kerr nonlinearity by measurement-induced quantum operations on weak quantum states of light. Our scheme coherently combines two sequences of single photon addition and subtraction to induce a nonlinear phase shift at the single photon level. We probe the induced nonlinearity with weak coherent states and characterize the output non-Gaussian states with quantum state tomography. The strong nonlinearity is clearly witnessed as a change of sign of specific off-diagonal density matrix elements in the Fock basis.

Generating Discorrelated States for Quantum Information Protocols by Coherent Multimode Photon Addition

“…For instance, using sequences of photon addition and subtraction operations, it is possible to realize enabling tools for optical quantum technologies, such as noiseless linear amplification [ 12 ] and measurement‐induced strong Kerr nonlinearity at the single‐photon level. [ 13 ] Moreover, when the single‐photon addition process is coherently applied to a multimode field, delocalized heralded addition can entangle two or more field modes. [ 14 ]…”

Procedure via cross-Kerr nonlinearities for encoding single logical qubit information onto four-photon decoherence-free states

“…For the interaction of XKNLs, the magnitude of XKNL can obtain to , due to the electromagnetically induced transparency 67 , 68 . Recently, to the measurement-induced quantum operation on weak quantum states of light 69 can generate a strong XKNL at the single photon level for the applicable quantum information processing. Also, for the Hamiltonian, , of XKNL with , the scheme 70 have been designed in circuit QED where is coupling strength, is the transition strength between levels driven by a classical pump field with , detuning.…”

Destructive Controlled-Phase Gate using Linear Optics

“…There have been several proposals to enhance the success rate of this gate at the expense of adding more resources 13,14 or vice-versa 15 . Costanzo et al 12 proposed an alternative implementation of a nonlinear sign gate that is shown in Figure 2. As illustrated in the upper part of the figure, the device produces a coherent superposition of photon subtractions that occur either before or after a photon addition.…”