CV Quantum Information
Non-reciprocal entanglement propagation
The basic idea in (Pelka et al., 2024) revolves around amorphous quantum networks—where the nodes consist of bosonic modes—which can be used in some sense to employ any quantum cryptographic scheme or quantum information processing. At some point it will be necessary to distribute quantum resources—such as entanglement—in a controllable manner in distinct nodes of the network. This is where our work comes into play.
We imagine an array of open bosonic quantum systems, depicted in the left picture, that are arranged such that there exist two different possibilities to hop from one node to the next. These can be tuned to enable nonreciprocal hopping such that any excitation that travels down the channel cannot travel back. Through connecting this quantum channel with an external, squeezed oscillator we generate quanta that are identical in their quantum properties. We investigate the steady state where these quanta have been propagated through the channel and see that the quantifier—the logarithmic negativity which is non-zero for entangled parties—shows entanglement if the directionality permits transmission of excitations.
Moreover we find that stronger squeezing reduces the amount of nodes that the entanglement can be propagated through the network even though it is the entanglement generating process. We link it to the amount of mean excitations that are generated in this process “heating” up the channel until it becomes unstable.
