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In their paper "Time-reversal-based quantum metrology with many-bodyentangled states" Nature Physics (2022), Colombo et. al. claim to measure bothan unknown phase and an oscillating magnetic field with a precision that cannotbe achieved using independent particles - a limit known as the standard quantumlimit. By entangling an ensemble of $\sim300$ atoms, Colombo et. al. measure anangle of rotation away from a known initial state and additionally measure amagnetic field oscillating at 290 Hz. The authors report an experimentalprecision approximately a factor of 4 beyond what is possible with the samenumber of independent atoms (12.8 dB and 11.8 dB for these tasks respectively).These claims are incorrect. Colombo et. al. do not surpass the precision boundfor 300 independent particles, nor do they even surpass the precision bound fora single particle. Colombo et. al. cite several experiments that surpass thestandard quantum limit using entanglement. Each and every paper cited performsincorrect, incomplete or misleading comparisons of the type that we highlighthere. The consequence being that the single particle precision bound has neverbeen experimentally surpassed with entanglement.

Matters Arising: Time-reversal-based quantum metrology with many-body entangled states