Yu Wang

PROBLEM:

• Gate density is high in the Kane’s proposal (Fig. a), which easily leads to gate shorting and crosstalk, challenging in fabrication

OBJECTIVE:

• To reduce gate density to avoid metal gate shorting and crosstalk.

APPROACH:

• Use detuning gates (Fig. b,c) instead of J-gates in Kane’s architecture (Fig. a) to control the exchange coupling (J).

RESULTS/IMPACT:

• Using detuning gates reduces the gate density, which is less challenging in fabrication without losing control of exchange.

PROBLEM:

• 1P-1P system in Kane’s proposal is prone to fabrication error. Large oscillations in exchange coupling in [110] were reported.

OBJECTIVE:

• To reduce the oscillations in exchange coupling in [110].

APPROACH:

• Use 2P-1P systems instead of 1P-1P systems.
• Modeling approach: atomistic tight-binding + full configuration interaction, which is accurate to capture multi-electron interactions.

RESULTS/IMPACT:

• Large J-oscillations in [110] in 1P-1P systems are strongly mitigated in asymmetric 2P-1P systems that are more stable.

PROBLEM:

• The gate tunability of exchange coupling in 1P-1P systems are limited.

OBJECTIVE:

• To obtain highly tunable exchange coupling in donor qubits in silicon.

APPROACH:

• To gain high tunability of exchange coupling, use 2P-1P instead of 1P-1P systems.

RESULTS/IMPACT:

• Exchange coupling of a 2P-1P system with inter-qubit separation of 15 nm can be tuned by 5 orders of magnitude with detuning gates.
• This work supports the practical realization of quantum computing architectures in silicon.