Noisy channels and study of finite time disentanglement in quantum systems

Lech Jakóbczyk, Anna Jamróz

Ting Yu, Joseph H. Eberly

It has been demonstrated in various ways, if not rigorously proven, that when a quantum system and an environment interact they become entangled extremely rapidly and are essentially impossible to disentangle. Another interesting matter has received little attention, namely whether non-local entanglement between small systems is more or less susceptible to rapid decay than local measures of system coherence. An instance of potential importance for solid state quantum computing arises if embedded qubit spins are exposed to both global and local noise at the same time. Here we show that phase-noisy channels affect local and non-local measures of system coherence differently. A consequence is that the time for entanglement decay can be significantly shorter than the time for complete local dephasing for two qubits.

Masanori Ohya, Noboru Watanabe

Xiaowei Deng, Caixing Tian, Xiaolong Su +1 more

A quantum communication network can be constructed by distributing a multipartite entangled state to space-separated nodes. Entangled optical beams with highest flying speed and measurable brightness can be used as carriers to convey information in quantum communication networks. Losses and noises existing in real communication channels will reduce or even totally destroy entanglement. The phenomenon of disentanglement will result in the complete failure of quantum communication. Here, we present the experimental demonstrations on the disentanglement and the entanglement revival of tripartite entangled optical beams used in a quantum network. We experimentally demonstrate that symmetric tripartite entangled optical beams are robust in pure lossy but noiseless channels. In a noisy channel, the excess noise will lead to the disentanglement and the destroyed entanglement can be revived by the use of a correlated noisy channel (non-Markovian environment). The presented results provide useful technical references for establishing quantum networks.

Michael Siomau, S. Fritzsche

Xiaowei Deng, Caixing Tian, Xiaolong Su +2 more

We demonstrate that the excess channel noise in a quantum network will lead to the disentanglement among three optical modes and the destroyed entanglement can be revived by using a correlated noisy channel.