Effect of control procedures on the evolution of entanglement in open quantum systems

TL;DR

This paper investigates how various control methods affect entanglement preservation in open quantum systems, revealing that some controls unexpectedly accelerate entanglement loss, especially in strong-coupling regimes.

Contribution

It provides a comparative analysis of different decoherence suppression techniques, highlighting their varied effects on entanglement dynamics in diverse quantum system-bath interactions.

Findings

Photonic band-gap materials and frequency modulation slow entanglement loss.

Resonance fluorescence control accelerates entanglement decay.

Dynamic decoupling slows decoherence in harmonic oscillator baths but can hasten entanglement death in non-Markovian regimes.

Abstract

The effect of a number of mechanisms designed to suppress decoherence in open quantum systems are studied with respect to their effectiveness at slowing down the loss of entanglement. The effect of photonic band-gap materials and frequency modulation of the system-bath coupling are along expected lines in this regard. However, other control schemes, like resonance fluorescence, achieve quite the contrary: increasing the strength of the control kills entanglement off faster. The effect of dynamic decoupling schemes on two qualitatively different system-bath interactions are studied in depth. Dynamic decoupling control has the expected effect of slowing down the decay of entanglement in a two-qubit system coupled to a harmonic oscillator bath under non-demolition interaction. However, non-trivial phenomena are observed when a Josephson charge qubit, strongly coupled to a random telegraph noise bath, is subject to decoupling pulses. The most striking of these reflects the resonance fluorescence scenario in that an increase in the pulse strength decreases decoherence but also speeds up the sudden death of entanglement. This demonstrates that the behaviour of decoherence and entanglement in time can be qualitatively different in the strong-coupling non-Markovian regime.