Overcoming Quantum Metrology Singularity through Sequential Measurements

Understand

The simultaneous estimation of multiple unknown parameters is the most general scenario in quantum sensing.

• Quantum multi-parameter estimation theory provides fundamental bounds on the achievable precision of simultaneous estimation.
• However, these bounds can become singular (no finite bound exists) in multi-parameter sensing due to parameter interdependencies, limited probe accessibility, and insufficient measurement outcomes.
• Here, we address the singularity issue in quantum sensing through a simple mechanism based on a sequential measurement strategy.