Scalable Neutral Atom Quantum Computer with Interaction on Demand: Proposal for Selective Application of Two-Qubit Gate

Abstract

We propose a scalable neutral atom quantum computer with an on-demand interaction through a selective two-qubit gate operation. Atoms are trapped by a lattice of near field Fresnel diffraction lights so that each trap captures a single atom. One-qubit gate operation is implemented by a gate control laser beam which is applied to an individual atom. Two-qubit gate operation between an arbitrary pair of atoms is implemented by sending these atoms to a state-dependent optical lattice and making them collide so that a particular two-qubit state acquires a dynamical phase. We give numerical evaluations corresponding to these processes, from which we estimate the upper bound of a two-qubit gate operation time and corresponding gate fidelity. Our proposal is feasible within currently available technology developed in cold atom gas, MEMS, nanolithography, and various areas in optics.

Two-Qubit Gate Operation on Selected Nearest-Neighbor Neutral Atom Qubits

“…The present setup is less demanding than the previous one proposed in Ref. [20] because it is no longer necessary to control the size of individual apertures for the NFFD traps. For this new setup, we have obtained an upper bound of the entangled gate operation time 8.45 ms with a corresponding fidelity of 0.923 bounded by the adiabaticity requirement.…”

“…The purpose of this work is to present a quantum computer scheme that is less demanding than our previous proposal [20]. There are primarily three difficulties in our previous proposal:…”

“…We will finally present, in detail, numerical calculations corresponding to the process of the two-qubit gate operation, from which we estimate the upper bound of the gate operation time and corresponding gate fidelity. Figure 1 shows the scheme of our recent proposal [20]. Neutral atoms with two hyperfine states, |0 and |1 , are trapped in an array of optical potentials generated by NFFD of light at thin apertures, each with a radius comparable to the wavelength of the light [21].…”

“…In order to implement a two-qubit gate operation between an arbitrary pair of atoms, a one-dimensional optical lattice is superimposed near the substrate by applying a pair of tightly-focused, counterpropagating laser beams along the atom trapping sites, so that the minima of the optical lattice are situated at the space coordinates for the atoms trapped in NFFD potentials. By manipulating the aperture size, one can control the position of an individual atom in a direction perpendicular to the aperture plane to transfer atoms into a one-dimensional optical lattice [20,23,24], as shown in Fig. 1(c).…”

“…Finally, the atoms are transferred from the optical lattice to the initial NFFD traps. As an example, we considered two hyperfine states |0 = |F = 1, m F = 1 and |1 = |F = 2, m F = 1 of 87 Rb atoms to be compatible with this scheme and estimated that the time required for the entangling gate operation is on the order of 10 ms with a corresponding fidelity of 0.886 [20].…”