Switching off the reservoir through nonstationary quantum systems

Abstract

In this paper we demonstrate that the inevitable action of the environment can be substantially weakened when considering appropriate nonstationary quantum systems. Beyond protecting quantum states against decoherence, an oscillating frequency can be engineered to make the system-reservoir coupling almost negligible. Differently from the program for engineering reservoir and similarly to the schemes for dynamical decoupling of open quantum systems, our technique does not require a previous knowledge of the state to be protected. However, differently from the previously-reported schemes for dynamical decoupling, our technique does not rely on the availability of tailored external pulses acting faster than the shortest time scale accessible to the reservoir degree of freedom.

Equivalence between Redfield- and master-equation approaches for a time-dependent quantum system and coherence control

“…This result is in perfect agreement with the one obtained in Ref. [16]. An important observation is that this protocol is completely independent of the temperature of the environment, as well as of the initial state of the system.…”

“…In contrast to the protocol in Ref. [16], in the present case, we do not imposed a functional form for the system-environment coupling, which emerges naturally from the Redfield semiclassical formalism. The coherence control of the spin-1/2 system was demonstrated by enlarging the longitudinal relaxation time through the modulation of the system frequency.…”

“…In Ref. [16] it was proposed a method to circumvent the decoherence process of a non-stationary system under amplitude-damping channel. In that work, the authors focused on the state protection of a cavity mode whose modulation of the frequency ω(t) was engineered through the atom-field interaction.…”

“…In fact, when the amplitude χ is smaller than the Lorentzian sharpness ξ, the non-stationary system does not leave the region (in frequency space) of its effective coupling with the environment, thus decaying as a stationary system, whatever the value of ζ. However, when χ is larger than ξ, the effective system-environment coupling moves to different regions of the spectrum, thus triggering the action of the rate of variation ζ as described above [16]. Now, we apply the same idea to the case of a spin-1/2 system considering the Redfield formalism to treat the decoherence process.…”

Upper bounded and sliced Jaynes– and anti-Jaynes–Cummings Hamiltonians and Liouvillians in cavity quantum electrodynamics

“…Moreover, engineered interactions are a precondition for the reservoir engineering technique, [5] where a target state is protected. The strategy of switching off the reservoir and thus protecting any quantum state, based on the engineering of a nonstationary quantum system -where a time-dependent Hamiltonian must be appropriately prepared-has also been advanced [6].…”