Atom-ion quantum gate

Abstract

We study ultracold collisions of ions with neutral atoms in traps. Recently, ultracold atom-ion systems are becoming available in experimental setups, where their quantum states can be coherently controlled. This allows for an implementation of quantum information processing combining the advantages of charged and neutral particles. The state-dependent dynamics that is a necessary ingredient for quantum computation schemes is provided in this case by the short-range interaction forces depending on hyperfine states of both particles. In this work we develop a theoretical description of spin-state-dependent trapped atom-ion collisions in the framework of a Multichannel Quantum Defect Theory (MQDT) and formulate an effective single channel model that reduces the complexity of the problem. Based on this description we simulate a two-qubit phase gate between a Ba135+ ion and a Rb87 atom using a realistic combination of the singlet and triplet scattering lengths. We optimize and accelerate the gate process with the help of optimal control techniques. Our result is a gate fidelity 0.999 within 350 microseconds.

15 pages, submitted to Phys. Rev. A, added references to Section I, corrected typos, improved Section III

References in corpus (6)

• Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms
• Quantum theory of ultracold atom-ion collisions
• Controlled collisions of a single atom and ion guided by movable trapping potentials
• Quantum Memory with Optically Trapped Atoms
• Controlled collisions of two ultracold atoms in separate harmonic traps
• Multiscale quantum-defect theory for two interacting atoms in a symmetric harmonic trap

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