Quantum state transfer between photons preloaded with quantum information

Quantum mechanics provides a ``disembodied'' way to transfer an unknown quantum state from one quantum system to another. However, all experiments of quantum state transfer to date are limited to cases where the target quantum system contains no prior quantum information. Here we propose a scheme for transferring a quantum state to a quantum system preloaded with quantum information. By using an optical qubit-ququart entangling gate, we have experimentally demonstrated this new protocol -- transferring a qubit to a photon preloaded with one qubit of quantum information. After the state transfer, the target photon contains two qubits of quantum information, one from the qubit being transferred and the other from the pre-existing qubit. Furthermore, we have also experimentally realized the inverse operation of the aforementioned quantum state transfer, which is called the partial quantum state transfer, namely transferring one qubit of quantum information from a photon preloaded with two qubits of quantum information to another photon. The fidelities of the quantum state transfer range from $0.700$ to $0.917$, all above the classical limit of $2/3$. Our work sheds light on a new direction for quantum state transfer and demonstrates our ability to implement entangling operations beyond two-level quantum systems.Comment: 22pages, 9 figure

Validated model of thermochemical energy storage based on cobalt oxides

Thermal Energy Storage (TES) can play a critical role through provision of reliable energy supply and increase the market penetration of renewable energy sources. Thermochemical Energy Storage (TCES) based on reversible reactions offers distinguished advantages in comparison with sensible and latent heat storage: higher energy density, higher temperature range and possibility of seasonal storage. TCES systems based on the redox cycle of metallic oxides shows significant potential for integration with Concentrated Solar Power (CSP) plants using air as the heat transfer fluid, which also acts as a reactant for the redox reaction. A pilot scale thermochemical storage reactor designed for a CSP plant has been developed and tested in the framework of a collaborative European funded project \u201cRESTRUCTURE\u201d at the Solar Tower Julich (STJ). TCES system is proposed with the aim of achieving higher energy storage capacity and higher storage temperature. Numerical modeling of a TCES prototype presented in this study is a contribution towards this effort. The present work is focused on the innovative one-dimensional modeling of a TCES system based on the redox cycle of cobalt oxides (Co3O4/CoO), coated on the ceramics honeycomb structures. The numerical model for TCES involved the energy balance and reaction kinetics describing the redox reaction of cobalt oxides, to simulate the phenomena of thermochemical storage. The simulation results were presented as the temperature profiles at different positions inside the storage vessel and they were validated against experimental data published in literature by other groups. This validation proved that this model can simulate the overall thermochemical storage process with reasonable accuracy. The simulation tool was also used to perform the parametric analysis of the storage module, which provides guidance to optimize the performance of the storage system. Moreover, due to its good compromise between reliability and computational time, the established 1-D thermochemical storage model can be integrated with the CSP plant model for dynamic analysis of the whole system, which is the aim of this study