Many-Body Dynamics in Monitored Atomic Gases without Postselection Barrier

Area of Science:

• Quantum optics
• Atomic physics
• Quantum information science

Background:

• Monitored quantum systems exhibit unique dynamics distinct from ensemble averages.
• Collective decay and laser driving influence atomic ensembles significantly.

Purpose of the Study:

• Investigate the properties of monitored atomic ensembles under laser driving and collective decay.
• Explore the impact of monitoring protocols on quantum trajectories and entanglement.
• Identify and characterize measurement-induced phase transitions.

Main Methods:

• Theoretical study of a monitored ensemble of atoms.
• Analysis of quantum trajectories under varying laser drive strengths.
• Calculation of entanglement entropy scaling with system size.
• Comparison with trajectory-averaged density matrix dynamics.

Main Results:

• Quantum trajectories show properties distinct from the average density matrix.
• A measurement-induced phase transition occurs with varying laser drive.
• Entanglement entropy scales subextensively in different phases.
• The critical point aligns with the superradiance transition in averaged dynamics.

Conclusions:

• Monitored atomic ensembles exhibit novel quantum phenomena, including measurement-induced phase transitions.
• The proposed setup is experimentally feasible with current technology.
• The monitored dynamics circumvents the postselection measurement problem, even with imperfect monitoring.