Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate

Abstract

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.

Optimization of segmented linear Paul traps and transport of stored particles

“…Starting with two-qubit gate operations [2,3], long lived two-qubit entanglement [4,5,6], teleportation experiments [7,8], and different sorts of multi-qubit entangled states [9,10,4,11], the record for qubit-entanglement is currently presented in a 6-qubit cat state and a 8-qubit W-state [12,13]. Future improvement is expected using the technique of segmented linear Paul traps which allow to shuttle ions from a "processor" unit to a "memory" section [14].…”

Energy evolution in the time-dependent harmonic oscillator with arbitrary external forcing

“…We have numerically obtained the characteristic function and the energy distribution for some particular values of the parameters for the general case, where the energy distribution function has four singularities, but in the small initial energy limit their number reduces to two, indeed. The results obtained can be useful in the context of geometric ion trap quantum computations [2,3] where the particular implementation of the investigated model of the time-dependent harmonic oscillator with external forcing plays the crucial role. More details can be found in [7,18].…”

“…The particular implementation of the quantized time-dependent harmonic oscillator with the external forcing is the key model exploited in geometrical ion trap quantum computations [2,3].…”

Sympathetic cooling in a large ion crystal

“…Numerous advances have been achieved in this system, including realization of faithful quantum gates [1][2][3][4][5][6][7], preparation of many-body quantum states [8][9][10][11][12][13][14][15], and quantum teleportation [16,17]. There are also developments to scale up this system, based on either ion shuttling [18][19][20] or quantum networks [21][22][23][24][25][26]).…”