Kavli Affiliate: Jing Wang
| First 5 Authors: Dongheng Qian, Dongheng Qian, , ,
| Summary:
Coherent information quantifies the transmittable quantum information through
a channel and is directly linked to the channel’s quantum capacity. In a
monitored quantum circuit, regarded as a quantum channel, extensive and
positive coherent information is sustained at low measurement rates, protected
by the scrambling dynamics. However, noise suppresses coherent information,
driving it to zero or negative values. Here, we show that incorporating
quantum-enhanced operations facilitates reliable quantum information
transmission even in the presence of noise, as evidenced by a phase transition
in coherent information from a recoverable phase with positive values to an
irrecoverable phase with negative values. We provide both analytical
understanding and numerical evidence demonstrating this transition, which is
modulated by the relative frequencies of noise and quantum-enhanced operations.
Additionally, we propose a resource-efficient protocol to characterize this
phase transition in experiments, effectively avoiding post-selection by
utilizing every run of the quantum circuit. This approach bridges the gap
between theoretical insights and practical implementation, making the phase
transition feasible to demonstrate on realistic noisy intermediate-scale
quantum devices.
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