Phys.org August 26, 2022 Measurement and feedback control are essential features of quantum science, with applications ranging from quantum technology protocols to information-to-work conversion in quantum thermodynamics. Theoretical descriptions of feedback control are typically given in terms of stochastic equations requiring numerical solutions or are limited to linear feedback protocols. An international team of researchers (Sweden, USA – University of Maryland, Switzerland) presented a formalism for continuous quantum measurement and feedback, both linear and nonlinear. The main result is a quantum Fokker-Planck master equation describing the joint dynamics of a quantum system and a detector with finite bandwidth. For fast […]
Tag Archives: Quantum measurement
Physicists harness quantum ‘time reversal’ to measure vibrating atoms
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 […]