Experimental investigation of environment-induced entanglement using an all-optical setup

We investigate the generation of entanglement between two noninteracting qubits coupled to a common reservoir. An experimental setup was conceived to encode one qubit on the polarization of an optical beam and another qubit on its transverse mode. The action of the reservoir is implemented as conditional operations on these two qubits, controlled by the longitudinal path as an ancillary degree of freedom. An entanglement witness and the two-qubit concurrence are easily evaluated from direct intensity measurements showing an excellent agreement with the theoretical prediction.

Figure 1

Experimental setup.

Figure 2

Double input/output MZIM.

Figure 3

cnot circuit.

Figure 4

Output images (false color) for (a) initial state ($t=0$) and (b) asymptotic state ($t\to \infty$). The population, shown at the bottom of each pair of images, is obtained by summing the grey scale distribution of the corresponding outputs.

Figure 5

Concurrence $C=max\{0,\mathrm{\Lambda }\}$ as a function of the parameter $p=1-e^{-\mathrm{\Gamma }t}$. Experimental values for $\mathrm{\Lambda }$ are represented by triangles, while the solid line represents the theoretical prediction for $C$.