Imperfect detectors still help qubits stay entangled longer

Roson Nongthombam and Amarendra K. Sarma of the Indian Institute of Technology Guwahati investigate the role of continuous measurement and postselection in the dynamics and entanglement of a transmon-cavity-transmon coupled system. Their work centers on a system where two superconducting qubits interact through a shared cavity, and demonstrates that combining continuous measurement with a technique called postselection significantly slows entanglement decay. These results offer insight into managing entanglement in quantum systems with potential applications in quantum information processing. The energy spectrum of a transmon-cavity-transmon system reveals a pathway to sustained entanglement. Their analysis demonstrates that, under specific conditions, the system exhibits oscillatory dynamics without decay in density matrix elements, directly correlating to entanglement that persists without diminishing. This behavior arises from tuning the external flux of the transmons to an avoided crossing point, enabling an exchange interaction and subsequent entanglement between the two qubits. The researchers explored the impact of continuous measurement…