Open Systems, Entanglement and Quantum Optics

Paul Renault, Johannes Nokkala, Ganaël Roeland +6 more

No quantum system can be considered totally isolated from its environment. In most cases the interaction between the system of interest and the external degrees of freedom deeply changes its dynamics, as described by open quantum system theory. Nevertheless, engineered environment can be turned into beneficial effects for some quantum information tasks. Here we demonstrate an optical simulator of a quantum system coupled to an arbitrary and reconfigurable environment built as a complex network of quantum interacting systems. We experimentally retrieve typical features of open quantum system dynamics like the spectral density and quantum non-Markovianity, by exploiting squeezing and entanglement correlation of a continuous variables optical platform. This opens the way to the experimental tests of open quantum systems in reconfigurable environments that are relevant in, among others, quantum information, quantum thermodynamics, quantum transport and quantum synchronization.

David S. Simon, Gregg S. Jaeger, Alexander V. Sergienko

Changsuk Noh

Quantum optics provides powerful means to probe quantum mechanics. In this \nthesis, we study various aspects of quantum phenomena arising in quantum optical \nsystems. Part I studies broadband quantum teleportation. After presenting three \ndifferent methods of analyzing the standard teleportation protocol, we study the \ninterplay between various bandwidths in determining the fidelity of a broadband \nquantum field teleportation. Explicit formulae for the degrees of first- and secondorder \ncoherence for the teleportation of resonance fluorescence are derived for this \npurpose. Part II studies entanglement arising in cascaded open quantum (optical) \nsystems. First, a detailed laser model is produced within quantum trajectory theory \nto study the total decoherence rate of a laser-driven qubit. Second, using this model, \nwe address the issue of laser quantum state, viewed in connection with separability \nof the laser-driven-qubit system. Third, a measure of entanglement within quantum \ntrajectory theory called ‘Contextual Entanglement’ is calculated for a few simple \nsystems and compared with the ‘Entanglement of Formation’. Lastly, we introduce \na method to quantify entanglement (based on the contextual entanglement) between \na source and the field it emits, which we call the ‘Entanglement Spectrum’. It is \napplied to study the entanglement between a laser-driven qubit and the field the \nqubit scatters.

Jin‐Shi Xu, Chuan‐Feng Li, Xiao‐Ye Xu +3 more

We experimentally characterize the bipartite entanglement under one-sided open system dynamics and verify the recently formulated entanglement factorization law [Nature Phys. 4, 99 (2008)]. The one-sided open system dynamics is realized by implementing a phase damping and an amplitude decay channel, respectively, acting on one of the qubits, by an all-optical setup. Our results greatly simplify the characterization of entanglement dynamics and will play an important role in the construction of complex quantum networks.