Ion-trap quantum logic using long-wavelength radiation

TL;DR

Ion-trap quantum information processing is limited by microwave radiation’s negligible coupling to ion motion and inability to address individual ions without focused lasers. The paper proposes an inhomogeneous magnetic-field gradient that couples internal and motional states and separates qubit resonances, enabling individual addressing and coherent manipulation with microwave radiation. The required gradients are within current experimental capabilities, although the gradient requirement grows with ion number and limits qubits per trap.

• Problem

  Microwave radiation cannot ordinarily couple ion internal and motional states or address individual ions, while optical schemes require demanding laser setups.

  Source: p. 1

• Method

  The scheme applies an inhomogeneous magnetic-field gradient to trapped ions to mediate internal–motional coupling and frequency-separate individual qubit resonances.

  Source: pp. 2–3

• Results

  The scheme permits coherent manipulation and individual addressing of trapped ions using microwave radiation, with required gradients within current experimental capabilities.

  Source: p. 4

• Takeaways & Limitations

  Ion-trap quantum-information techniques can be implemented using microwave radiation in conjunction with trapped-ion and NMR technology, including possible multi-qubit operations.

  Source: p. 4

  The required magnetic-field gradient grows with the number of ions stored in one trap, limiting the number of qubits available there.

  Source: p. 3