Nuclear spin quantum register in an optically active semiconductor quantum dot

Area of Science:

• Quantum computing
• Semiconductor nanotechnology
• Quantum information science

Background:

• Epitaxial quantum dots (QDs) are promising charge spin qubits for quantum light interfaces and semiconductor nanofabrication.
• Charge spin coherence in QDs is often limited by interactions with atomic nuclear spins, especially in strained dots.

Purpose of the Study:

• To demonstrate a functional two-qubit quantum register using nuclear spins in strain-free GaAs/AlGaAs quantum dots.
• To explore the potential of nuclear spins as a quantum information resource within QD circuits.

Main Methods:

• Utilized strain-free GaAs/AlGaAs quantum dots.
• Employed tailored radio-frequency pulses for quantum state storage and control.
• Implemented optical initialization and readout techniques.
• Performed benchmark quantum computations, including Grover's search and Deutsch-Jozsa algorithm.

Main Results:

• Achieved a fully functioning two-qubit quantum register using arsenic quadrupolar nuclear spins.
• Demonstrated quantum state storage for up to 20 milliseconds.
• Attained single- and two-qubit gate fidelities exceeding 97% with microsecond control.
• Successfully executed benchmark quantum algorithms.

Conclusions:

• Quantum dot nuclei can serve as a viable quantum information resource.
• This nuclear spin-based approach complements charge spins and photons in future QD quantum circuits.
• High-fidelity control and long coherence times are achievable using this method.