Decoherence in strongly coupled quantum oscillators

Ponte, M. A. de; Oliveira, M. C. de; Moussa, M. H. Y.

doi:10.1016/j.aop.2004.12.007

Cited by 35 publications

(91 citation statements)

References 58 publications

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“…We assume that the interactions between the resonators of frequencies ω m and ω n are within the rotating wave approximation with coupling strength λ mn . In what follows we analyze both the weak and strong coupling regimes between the resonators, where N λ mn ≪ ω m′ and N λ mn ω m′ , respectively [12]. We also investigate the special case of the weak coupling regime, of negligible mutual interaction between the resonators, where…”

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Relaxation- and decoherence-free subspaces in networks of weakly and strongly coupled resonators

2007

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We consider a network of interacting resonators and analyze the physical ingredients that enable the emergence of relaxation-free and decoherence-free subspaces. We investigate two different situations: i) when the whole network interacts with a common reservoir and ii) when each resonator, strongly coupled to each other, interacts with its own reservoir. Our main result is that both subspaces are generated when all the resonators couple with the same group of reservoir modes, thus building up a correlation (among these modes), which has the potential to shield particular network states against relaxation and/or decoherence.The search for mechanisms to bypass decoherence, a subject of major concern for quantum information processing, has deepened our understanding of open quantum systems and led to ingenious schemes for coherence control, which go far beyond the quest for conditions that weaken the system-reservoir coupling [1,2]. The myriad contributions to this subject started, inspired by classical error-correcting codes, with quantum coding schemes for information stored in a quantum memory [3]. On the assumption that the decoherence process acts independently on each of the qubits stored in a memory, a particular qubit encoded in a block of ancillary qubits is able to withstand a substantial degree of interaction with the reservoir without degradation of its information. Another strategy, the so-called engineering reservoirs [4], compels the system of interest, whose state is to be protected against decoherence, to engage in additional interactions besides that with the reservoir. This program, based on the indirect control of system-reservoir dynamics, has been developed for trapped ions [5,6] and atomic two-level systems [7,8] as well. Finally, the process of collective decoherence, where a composite system interacts with a common reservoir, has also instigated several interesting results related to what has been called a decoherence-free subspace (DFS) [9,10,11]. It is noteworthy that while quantum error-correcting codes presuppose quantum systems that decohere independently, DFS -as it has been understood until the present study -is generated by distinct quantum systems coupled to a common reservoir.In this contribution we are concerned with collective dissipation and decoherence in a network of N coupled resonators. We analyze the physical ingredients ruling the emergence of a DFS and, in particular, a relaxationfree subspace (RFS) composed of states protected against both dissipation and decoherence, demonstrating that a DFS contains a RFS. We first analyze the situation, treated in the literature to date, where all the resonators are coupled to a common reservoir. However, as the scenario of a common reservoir is in practice rather unusual, we next analyze the situation where each resonator interacts with its own reservoir, which seems to be more appropriate for most physical systems. In the domain of cavity quantum electrodynamics, distinct reservoirs must be considered for distinguishable cavities,...

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“…[12] and noting that C mn < 1, we obtain, at T = 0K, the master equation of the reduced system of resonators…”

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Relaxation- and decoherence-free subspaces in networks of weakly and strongly coupled resonators

2007

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“…The issue of the physical grounds for the assumptions behind a common or distinct reservoirs is in detail in Ref. [12].…”

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“…(11) and (12). Starting with the parameter κ = Γ 0 /ζ, a measure of the rate of variation of the frequency ζ, compared to the damping constant Γ 0 , it is evident from Eq.…”

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Switching off the reservoir through nonstationary quantum systems

Céleri

Ponte

Villas-Bôas

et al. 2008

J. Phys. B: At. Mol. Opt. Phys.

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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.

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“…For linearly damped oscillators the decoherence terms in D 12 would only arise if Γ 1 = Γ 2 [41]. There is no such restriction however for the nonlinearly damped system where the superoperator D 12 consists of two decoherence terms, proportional to Υ + and Υ − respectively.…”

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confidence: 99%

Entanglement dynamics of quantum oscillators nonlinearly coupled to thermal environments

Voje

Isacsson

2015

Phys. Rev. A

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We study the asymptotic entanglement of two quantum harmonic oscillators nonlinearly coupled to an environment. Coupling to independent baths and a common bath are investigated. Numerical results obtained using the Wangsness-Bloch-Redfield method are supplemented by analytical results in the rotating wave approximation. The asymptotic negativity as function of temperature, initial squeezing and coupling strength, is compared to results for systems with linear system-reservoir coupling. We find that due to the parity conserving nature of the coupling, the asymptotic entanglement is considerably more robust than for the linearly damped cases. In contrast to linearly damped systems, the asymptotic behavior of entanglement is similar for the two bath configurations in the nonlinearly damped case. This is due to the two-phonon system-bath exchange causing a supression of information exchange between the oscillators via the bath in the common bath configuration at low temperatures.

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Decoherence in strongly coupled quantum oscillators

Cited by 35 publications

References 58 publications

Relaxation- and decoherence-free subspaces in networks of weakly and strongly coupled resonators

Relaxation- and decoherence-free subspaces in networks of weakly and strongly coupled resonators

Switching off the reservoir through nonstationary quantum systems

Entanglement dynamics of quantum oscillators nonlinearly coupled to thermal environments

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