Semiconductor Qubits

Silicon quantum dots, GaAs quantum dots, and phosphorus donor qubits

Trapping Technique

1. Electrons confined in quantum dots using electrostatic gates on semiconductor surface
2. Gate voltages create potential wells that trap individual electrons
3. Multiple gates control dot size, position, and tunnel coupling
4. Donor atoms (e.g., phosphorus) embedded in silicon crystal lattice
5. Donor electrons naturally bound to dopant nuclei in lattice sites
6. Isotopically pure silicon-28 reduces decoherence from nuclear spins

Gate Mechanism

1. Single-qubit gates via microwave pulses resonant with electron spin transitions
2. Electric field control via gate voltages shifts qubit energy levels
3. Electron spin resonance (ESR) drives spin rotations
4. Nuclear spin gates use radiofrequency pulses for nuclear spin qubits
5. Two-qubit gates via exchange interaction when quantum dots are tunnel-coupled
6. Exchange coupling strength controlled by gate voltages adjusting tunnel barrier
7. Capacitive coupling can also mediate long-range interactions