Fast Quantum Gates for Neutral Atoms

Abstract

We propose several schemes for implementing a fast two-qubit quantum gate for neutral atoms with the gate operation time much faster than the time scales associated with the external motion of the atoms in the trapping potential. In our example, the large interaction energy required to perform fast gate operations is provided by the dipole-dipole interaction of atoms excited to low-lying Rydberg states in constant electric fields. A detailed analysis of imperfections of the gate operation is given.

Many-body physics with alkaline-earth Rydberg lattices

“…Combining high-lying Rydberg states with cold atomic gases provides an appealing approach, as the strong long range van der Waals interactions between Rydberg atoms cause strongly correlated, many-body quantum states to emerge directly as Rydberg atoms are excited in dense clouds of cold atoms. The strong interactions inhibit the excitation of neighbouring atoms to the Rydberg state in an effect known as the dipole blockade [1,2]. This effect has been elegantly demonstrated in experiments using two independently trapped atoms [3,4], where it has also been exploited to entangle qubits [5], and perform gate operations [6,7].…”

Control of rubidium low-lying Rydberg states with trichromatic femtosecond π pulses for ultrafast quantum information processing

“…A central issue is the design of fast quantum gates, with recent proposals using neutral atoms and molecules that allow gate operation times set by the time scale of the laser excitation [3][4][5]. In the case of neutral atoms, the requirement that the gate operation time is short compared to the typical time of decoherence mechanisms, including spontaneous emission, collisions, ionization of the Rydberg states, transitions induced by black body radiation, or motional excitation of the atoms trapped in an optical lattice, leads to the search of state-selective Rydberg excitation schemes using femtosecond pulses.…”

“…These different schemes address the excitation of relatively high Rydberg levels, typically of principal quantum numbers as n ∼ 30. Several models have recently been proposed however to implement fast quantum gates in neutral atoms by using specific low-lying Rydberg states [3,4], for which faster femtosecond time scale selective coherent excitation schemes are demanded.…”

Grover search algorithm with Rydberg-blockaded atoms: quantum Monte Carlo simulations

“…The interactioninduced level shifts suppress resonant optical excitation of Rydberg states of more than one atom within a certain blockade distance from each other [1,2]. This blockade effect can then be used to implement quantum logic gate operations between closely spaced atoms [3][4][5][6][7][8], or to realize atomic ensemble qubits with Rydberg superatoms which can accommodate at most one collective Rydberg excitation at a time [9][10][11][12][13].…”