Is Wave Function Collapse Needed? Understanding Quantum Nondemolition Measurement of a Spin Qubit Using Linear Evolution

High fidelity measurements of a quantum dot electron spin qubit reached approximately 99.85%.

• Single-shot measurements achieved high accuracy due to a large number of nuclear spins in the ancilla.
• Repeated measurements supported the initialization of the qubit and detection of electron spin transitions.
• Electron spin quantum jumps were linked to fluctuations in a thermal environment.
• Results suggest that quantum state measurements can occur without necessitating 'wave function collapse'.
• Findings align with the concept of Quantum Darwinism, which relates quantum states to classical observations.

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