Quantum Effects in Higher-Order Correlators of a Quantum-Dot Spin Qubit

Area of Science:

• Quantum physics
• Solid-state systems
• Quantum information science

Background:

• Spin qubits in quantum dots are promising for quantum computing.
• Understanding quantum dephasing is crucial for qubit stability.
• Classical physics cannot fully explain certain quantum phenomena.

Purpose of the Study:

• To develop a method for measuring higher-order time correlators of spin qubits.
• To demonstrate that these correlators reveal purely quantum effects.
• To enable direct determination of quantum dephasing times without coherent spin control.

Main Methods:

• Measurement of time correlators beyond second order for a spin qubit.
• Utilizing repeated projective measurements.
• Application to optically active quantum dots.

Main Results:

• Higher-order correlators are sensitive to quantum effects beyond classical descriptions.
• Direct determination of ensemble dephasing time (T_{2}*) and quantum dephasing time (T_{2}) is achieved.
• The method successfully tested Leggett-Garg inequalities, ruling out local hidden variables.

Conclusions:

• The developed method provides a new pathway to study quantum behavior in solid-state systems.
• It allows for precise measurement of dephasing times using simpler experimental setups.
• This work contributes to foundational tests of quantum mechanics in solid-state qubits.