Decoupling-free NMR quantum computer on a quantum spin chain

Abstract

A method of switching a controlled-NOT gate in a solid-stae NMR quantum computer is presented. Qubits of I = 1/2 nuclear spins are placed periodically along a quantum spin chain (1-D antiferromagnet) having a singlet ground state with a finite spin gap to the lowest excited state caused by some quantum effect. Irradiation of a microwave tuned to the spin gap energy excites a packet of triplet magnons at a specific part of the chain where control and target qubits are involved. The packet switches on the Suhl-Nakamura interaction between the qubits, which serves as a controlled NOT gate. The qubit initialization is achieved by a qubit initializer consisting of semiconducting sheets attached to the spin chain, where spin polarizations created by the optical pumping method in the semiconductors are transferred to the spin chain. The scheme allows us to separate the initialization process from the computation, so that one can optimize the computation part without being restricted by the initialization scheme, which provides us with a wide selection of materials for a quantum computer.

Optical-pumping double-resonance NMR system for semiconductors

“…Decoupling pulse for X is not applied at the signal acquisition. application is to utilize it for a nuclear spin polarizer, 10,11 which is a hyperpolarization transfer scheme between heterogeneous materials using surfaces of semiconductors, originally proposed by Tycko. 12 We expect that the scheme will be useful as a signal enhancer in magnetic resonance force microscopes, 13 and a polarizer and a scatterer in polarized neutron scattering experiments.…”

Development of a dynamic nuclear polarization system based on the optical pumping method

“…In order to enhance its performance and to extend the range of its applications, we have developed a system so as to be able to perform cross-polarization under the optical pumping condition. The purpose of the new system is to transfer hyperpolarization of nuclear spins created by the optical pumping to another nuclear system using cross polarization [4][5][6].…”

Development of an Optical Pumping Nuclear Spin Polarizer

“…We extend the idea so as to enhance the transfer efficiency, i.e., the semiconductor (polarizer) and the target material are put contact with each other in a nanometer scale, and polarization in the polarizer is transferred to the target material through the interfaces using cross-polarization (CP) and nuclear spin diffusion. We named this scheme "optical pumping nuclear spin polarizer" (OPNSP) [3], [4].…”