Two-electron spin correlations in precision placed donors in silicon

Area of Science:

• Quantum computing
• Solid-state physics
• Materials science

Background:

• Substitutional donor atoms in silicon are promising qubits due to their long relaxation and dephasing times.
• Scaling silicon quantum computing requires precise control over inter-donor distances for wavefunction overlap and high-fidelity spin readout.

Purpose of the Study:

• To develop a device for controllable wavefunction overlap and high-fidelity spin readout in silicon-based donor qubits.
• To demonstrate electrical control of exchange interaction between donor qubits.

Main Methods:

• Utilized scanning tunneling microscopy lithography to fabricate the device.
• Measured anti-correlated spin states between two donor qubits separated by 16 ± 1 nm.
• Employed an asymmetric 2P-1P donor system with in-plane phosphorus-doped detuning gates for electrical control.

Main Results:

• Achieved precise inter-donor distance control (16 ± 1 nm) for silicon qubits.
• Demonstrated electrical switching of exchange interaction in a 2P-1P donor system.
• Determined the tunnel coupling between the 2P-1P system to be 200 MHz.

Conclusions:

• The developed device enables controllable wavefunction overlap and high-fidelity spin readout for silicon donor qubits.
• Electrical control of exchange interaction is feasible, paving the way for coherent operations.
• Provides a roadmap for observing two-electron coherent exchange oscillations, crucial for quantum computation.