Quantum entanglement is the core resource of quantum computing, and the ability of quantum computing will increase exponentially with the number of entangled bits. Therefore, the synchronous preparation of high quality entangled particle pairs is the first condition to realize large-scale entanglement. However, due to the quality of the entangled pair and the precision of the quantum logic gate, there is still a big gap between the number of entangled bits and fidelity needed for the practical quantum calculation and Simulation of the maximum entangled state distance that people can prepare.
Optical lattice supercooled atomic bits and superconducting bits have good scalability and high-precision quantum manipulation, which is the most likely system to achieve large-scale quantum entanglement. For the first time, the research team proposed a new refrigeration mechanism that uses staggered lattice structure to soak cold atoms in insulating state into superfluid state. Through the exchange of efficient atoms and entropy between insulating state and superfluid state, the heat in the system is mainly stored in the form of superfluid low energy excitation, and then the superfluid state is removed by precise control means, so as to obtain the perfect filled crystal with low entropy Lattice. After refrigeration, the entropy of the system is reduced 65 times, reaching a record low entropy, and the filling rate of atoms in the lattice is greatly increased to 99.9%. On this basis, they developed a two atom bit high-speed entanglement gate and obtained 1250 pairs of entangled atoms with 99.3% entanglement fidelity.
On this basis, the research team will prepare tens to hundreds of atom bits of entangled states by connecting multiple pairs of entangled atoms to carry out one-way quantum computation and quantum simulation of complex strong correlation multi-body system. At the same time, the new refrigeration technology in this work will be helpful to the deep cooling of the supercooled fermion system, and make the system reach the critical temperature region simulating the physical mechanism of high temperature superconductivity. The research results will greatly promote the development of quantum computing and simulation.
Source: Qiao JunJing, editor in charge of science and Technology Daily_ NBJ11279