Decoupling-free NMR quantum computer on a quantum spin chain

作者：Goto A^*; Shimizu T; Hashi K; Kitazawa H; Ohki S

来源：Physical Review A, 2003, 67(2): 022312.

DOI：10.1103/PhysRevA.67.022312

We propose a decoupling-free nuclear-spin quantum computer installed on a quantum electron spin chain with a singlet ground state and a finite spin gap. Qubits are I=1/2 nuclear spins implanted periodically along the quantum spin chain. A magnetic field gradient is applied parallel to the chain, which allows individual access to each qubit. A single-qubit operation (rotation gate) is realized with the rf field tuned to the nuclear Larmor frequency at the qubit of interest, while a two-qubit operation (controlled-NOT gate) is achieved using the Suhl-Nakamura interaction through a packet of triplet magnons, which are excited by a microwave tuned to the spin gap energy (SN gate). The interaction can be switched off by turning off the microwave, and a decoupling-free quantum computer is realized. The initialization is achieved with an optical pumping qubit initializer, which has a multilayered structure of the quantum spin chain and a semiconductor. Spin polarizations created by the optical pumping in the semiconducting layers are transferred to the spin chain layers through a cross polarization and a spin diffusion. The scheme allows us to separate the initialization process from the computation, enabling us to optimize the latter independently of the former.

• 出版日期2003-2