Quantum Phononics And Quantum Simulation In Solid Quantum Information Processing Systems

As component size reaches its limit,quantum effects in traditional integrated cir-cuits become more and more obvious.Therefore,studies on quantum technologies are attracting more attentions.Competition for guidance in quantum field has risen to the level of national strategy.The quantum technologies mainly include quantum communi-cation,quantum computation,quantum simulation and quantum detection etc..There are many experiment platforms,such as superconducting system,quantum dot,NV center,NMR,ultra-cold atoms and trapped ion etc..This article is mainly taking about quantum phononics in quantum information processing system and the quantum simulation using Jaynes-Cummings lattice model.Coupling between two level systems and a mechanical oscillator has widely applica-tions in the quantum information processing.Here,the second order magnetic gradient induced coupling between NV center and the mechanical oscillator is introduced.By driv-ing one mode of the oscillator,strong coupling between NV center and other modes of the oscillator can be realized,which can reach as high as 250kHz.Based on the strong coupling,state entanglement and state transfer and mode squeezing can be achieved.As quantum phononic components are widely applied in the quantum information processing,quantum phononics are making great progresses.In order to study it,a quan-tum phonon source is required.Next,in this article,a four-level structure is constructed by combining three ground state levels and one excited level in the NV centers and this four-level system is interacting with the quantum phonon.Under external optic and microwave driving,a giant polariton nonlinear effect can be obtained,and the single phonon source is realized based on this giant polariton nonlinear effect.The second order correlation func-tion of the polariton satisfies g(2)(0)<1,which confirms the quantum statistic property of the phonon source.Quantum simulation is using controllable quantum systems to explore other quantum systems and is a hot field in modern quantum physics.Jaynes-Cummings lattice model can be used as a quantum simulator,and this article approximately shows its low excited phase diagram.By regarding the two level system in each site as hard-core boson,low excited energy bands are obtained.When there is no band overlap for the lowest energy band,ground state of the system is in Mott insulator phase;Otherwise,the ground state of the system is in Superfluid phase.Then,quantum phase diagram is obtained,which is very similar to the phase diagram of Bose-Hubbard model.Initial state preparation is the first step to do quantum simulation.In the last part,this article is discussing how to prepare the initial ground state in coupled-cavity array(CCA)system.On average,there is only one excitation in each site.The CCA is initially biased in the deep Mott-insulating or the deep superfluid regime far from the quantum critical point.Then the system parameters are tuned adiabatically towards the different target parameters.Different evolution ways are tried.In Mott insulator phase,when the parameter evolution is proportional to t,the best fidelity can be got;However,in Superfluid phase,the parameter evolution which is proportional to t1/5 gives the best fidelity.