Coherent and incoherent theories for photosynthetic energy transfer

There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent effects have been experimentally demonstrated. Traditionally, the incoherent theories are capable of calculating the energy transfer efficiency, e.g.,(generalized) F?rster theory and modified Redfield theory(MRT). However, in order to describe the quantum coherent effects in photosynthesis, one has to exploit coherent theories, such as hierarchical equation of motion(HEOM), quantum path integral, coherent modified Redfield theory(CMRT), small-polaron quantum master equation, and general Bloch-Redfield theory in addition to the Redfield theory. Here, we summarize the main points of the above approaches,which might be beneficial to the quantum simulation of quantum dynamics of exciton energy transfer(EET) in natural photosynthesis, and shed light on the design of artificial light-harvesting devices.

Efficient quantum simulation of open quantum dynamics at various Hamiltonians and spectral densities

Simulation of open quantum dynamics for various Hamiltonians and spectral densities are ubiquitous for studying various quantum systems.On a quantum computer,only log2N qubits are required for the simulation of an N-dimensional quantum system,hence simulation in a quantum computer can greatly reduce the computational complexity compared with classical methods.Recently,a quantum simulation approach was proposed for studying photosynthetic light harvesting[npj Quantum Inf.4,52(2018)].In this paper,we apply the approach to simulate the open quantum dynamics of various photosynthetic systems.We show that for Drude—Lorentz spectral density,the dimerized geometries with strong couplings within the donor and acceptor clusters respectively exhibit significantly improved efficiency.We also demonstrate that the overall energy transfer can be optimized when the energy gap between the donor and acceptor clusters matches the optimum of the spectral density.The effects of different types of baths,e.g.,Ohmic,sub-Ohmic,and super-Ohmic spectral densities are also studied.The present investigations demonstrate that the proposed approach is universal for simulating the exact quantum dynamics of photosynthetic systems.

Efficient generation of NOON states on two microwave-photon resonators

We present an efficient scheme for the generation of NOON states of photons in circuit QED assisted by a superconducting charge qutrit.It is completed with two kinds of manipulations,that is,the resonant operation on the qutrit and the resonator,and the single-qubit operation on the qutrit,and they both are high-fidelity operations.Compared with the one by a superconducting transmon qutrit proposed by Su et al.(Sci Rep 4:3898,2014),our scheme does not require to maintain the qutrit in the third excited state with a long time,which relaxes the difficulty of its implementation in experiment.Moreover,the level anharmonicity of a charge qutrit is larger and it is better for us to tune the different transitions of the charge qutrit resonant to the resonator,which makes our scheme faster than others.