I am working on twisted bilayer graphene (TBG) by momentum-space continuous-field quantum Monte Carlo (CFMC) and exact diagonalization (ED). Hamiltonian dynamics are implied in my Monte Carlo method so that we can simulated a TBG system with a system size up to 21*21, which far transcends a discretized-field Monte Carlo method (DQMC) dealing with the system size up to at most 9*9. So, we can say CFMC is 1000 times faster than DQMC when dealing with TBG. On ED, for pristine TBG, there are two good quantum numbers, the momentum and the Chern number. By this two invariances, the ground state of a 6*6 TBG can be solved by ED.