Phys.org July 14, 2022
Linear quantum measurements with independent particles are bounded by the standard quantum limit, which limits the precision achievable in estimating unknown phase parameters. The standard quantum limit can be overcome by entangling the particles, but the sensitivity is often limited by the final state readout, especially for complex entangled many-body states with non-Gaussian probability distributions. By implementing an effective time-reversal protocol in an optically engineered many-body spin Hamiltonian a team of researchers in the US (MIT, Harvard University) has demonstrated a quantum measurement with non-Gaussian states with performance beyond the limit of the readout scheme. This signal amplification through a time-reversed interaction achieves the greatest phase sensitivity improvement beyond the standard quantum limit demonstrated to date in any interferometer. According to the researchers these results open the field of robust time-reversal-based measurement protocols offering precision not too far from the Heisenberg limit. Potential applications include quantum sensors that operate at finite bandwidth, and the principle they demonstrated may also advance areas such as quantum engineering, quantum measurements and the search for new physics using optical-transition atomic clocks…read more. TECHNICAL ARTICLEÂ
Setup and sequence. Credit: Nature Physics (2022)Â