Recovering quantum correlations in classical environments without backaction: observation and interpretation

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Abstract

Quantum correlations (entanglement, discord, nonlo-cality) present in a composite quantum system are essential resources for quantum information processing [1, 2]. However, the exploitation of these quantum resources is jeopardized by the detrimental effects of the environment surrounding the quantum system. For instance under Markovian noise, they decay asymptotically or disappear at a finite time [3, 4]. This drawback leads one to look for conditions where quantum correlations can be recovered during the evolution. To this aim non-Markovian noise, arising from strong couplings or structured environments, has been shown to be fundamental because of its memory effects. In fact, in the case of qubits in independent non-Markovian quantum environments, quantum corre- lations exhibit a combination of asymptotic decay with disappearance and revival [2, 5, 6], permitting their partial recovery and thus an extension of their use.Typically, for composite quantum systems within inde- pendent quantum environments, revivals of quantum cor- relations are interpreted as due to correlation exchanges induced by the back-action of non-Markovian quantum environments on the system (flows of quantum informa- tion back and forth from systems to quantum environments) [8-11]. Recently, it has been shown that revivals of quantum correlations may also occur when the envi- ronment is classical, thus unable to store quantum corre- lations, and forbids system-environment back-action [12- 18]. This fact naturally leads to basic issues on the in- terpretation of back-action-free quantum revivals, in par- ticular about: (i) the role of a classical environment in reviving quantum correlations, for instance if it may act as a control system for what operation is applied to the qubits; (ii) the role of collective effects of the environ- ment on the qubits; (iii) the role of the memory effects; (iv) the role of possible system-environment correlations.In this presentation, I first make a brief overview of some theoretical results about revivals of entanglement in classical environments. I describe a model of two nonin- teracting qubits, initially entangled, where only one qubit is subject to a random external classical field (a laser with two random phases) with inhomogeneous broadening in its amplitude [18]. I then report the results of an all- optical experiment that simulates this model and allows us to observe and control revivals of quantum correlations without system-environment back-action [18]. Finally, Idiscuss about non-Markovianity and provide a possible interpretation showing the role of the classical environ- ment in this phenomenon.The findings so far reveal that the revivals of quantum correlations are a dynamical feature of composite open systems irrespective of the nature, classical or quantum, of the environment. These results introduce the possibil- ity to recover and control, against decoherence, quantum resources even in absence of back-action, without resort- ing to demanding quantum structured environments or quantum error correction procedures and open the way to further studies concerning quantum correlation dynamics in classical environments.[1] R. Horodecki, P. Horodecki, M. Horodecki, and K.Horodecki, Rev. Mod. Phys. 81, 865 (2009).[2] K. Modi, A. Brodutch, H. Cable, T. Paterek, and V.Vedral, Rev. Mod. Phys. 84, 1655 (2012).[3] T. Yu and J. H. Eberly, Science 323, 598 (2009).[4] J.-S. Xu et al., Nature Commun. 1, 7 (2010).[5] R. Lo Franco, B. Bellomo, S. Maniscalco, and G. Com-pagno, Int. J. Mod. Phys. B 27, 1345053 (2013).[6] J.-S. Xu et a
Lingua originaleEnglish
Numero di pagine1
Stato di pubblicazionePublished - 2014

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title = "Recovering quantum correlations in classical environments without backaction: observation and interpretation",
abstract = "Quantum correlations (entanglement, discord, nonlo-cality) present in a composite quantum system are essential resources for quantum information processing [1, 2]. However, the exploitation of these quantum resources is jeopardized by the detrimental effects of the environment surrounding the quantum system. For instance under Markovian noise, they decay asymptotically or disappear at a finite time [3, 4]. This drawback leads one to look for conditions where quantum correlations can be recovered during the evolution. To this aim non-Markovian noise, arising from strong couplings or structured environments, has been shown to be fundamental because of its memory effects. In fact, in the case of qubits in independent non-Markovian quantum environments, quantum corre- lations exhibit a combination of asymptotic decay with disappearance and revival [2, 5, 6], permitting their partial recovery and thus an extension of their use.Typically, for composite quantum systems within inde- pendent quantum environments, revivals of quantum cor- relations are interpreted as due to correlation exchanges induced by the back-action of non-Markovian quantum environments on the system (flows of quantum informa- tion back and forth from systems to quantum environments) [8-11]. Recently, it has been shown that revivals of quantum correlations may also occur when the envi- ronment is classical, thus unable to store quantum corre- lations, and forbids system-environment back-action [12- 18]. This fact naturally leads to basic issues on the in- terpretation of back-action-free quantum revivals, in par- ticular about: (i) the role of a classical environment in reviving quantum correlations, for instance if it may act as a control system for what operation is applied to the qubits; (ii) the role of collective effects of the environ- ment on the qubits; (iii) the role of the memory effects; (iv) the role of possible system-environment correlations.In this presentation, I first make a brief overview of some theoretical results about revivals of entanglement in classical environments. I describe a model of two nonin- teracting qubits, initially entangled, where only one qubit is subject to a random external classical field (a laser with two random phases) with inhomogeneous broadening in its amplitude [18]. I then report the results of an all- optical experiment that simulates this model and allows us to observe and control revivals of quantum correlations without system-environment back-action [18]. Finally, Idiscuss about non-Markovianity and provide a possible interpretation showing the role of the classical environ- ment in this phenomenon.The findings so far reveal that the revivals of quantum correlations are a dynamical feature of composite open systems irrespective of the nature, classical or quantum, of the environment. These results introduce the possibil- ity to recover and control, against decoherence, quantum resources even in absence of back-action, without resort- ing to demanding quantum structured environments or quantum error correction procedures and open the way to further studies concerning quantum correlation dynamics in classical environments.[1] R. Horodecki, P. Horodecki, M. Horodecki, and K.Horodecki, Rev. Mod. Phys. 81, 865 (2009).[2] K. Modi, A. Brodutch, H. Cable, T. Paterek, and V.Vedral, Rev. Mod. Phys. 84, 1655 (2012).[3] T. Yu and J. H. Eberly, Science 323, 598 (2009).[4] J.-S. Xu et al., Nature Commun. 1, 7 (2010).[5] R. Lo Franco, B. Bellomo, S. Maniscalco, and G. Com-pagno, Int. J. Mod. Phys. B 27, 1345053 (2013).[6] J.-S. Xu et a",
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N2 - Quantum correlations (entanglement, discord, nonlo-cality) present in a composite quantum system are essential resources for quantum information processing [1, 2]. However, the exploitation of these quantum resources is jeopardized by the detrimental effects of the environment surrounding the quantum system. For instance under Markovian noise, they decay asymptotically or disappear at a finite time [3, 4]. This drawback leads one to look for conditions where quantum correlations can be recovered during the evolution. To this aim non-Markovian noise, arising from strong couplings or structured environments, has been shown to be fundamental because of its memory effects. In fact, in the case of qubits in independent non-Markovian quantum environments, quantum corre- lations exhibit a combination of asymptotic decay with disappearance and revival [2, 5, 6], permitting their partial recovery and thus an extension of their use.Typically, for composite quantum systems within inde- pendent quantum environments, revivals of quantum cor- relations are interpreted as due to correlation exchanges induced by the back-action of non-Markovian quantum environments on the system (flows of quantum informa- tion back and forth from systems to quantum environments) [8-11]. Recently, it has been shown that revivals of quantum correlations may also occur when the envi- ronment is classical, thus unable to store quantum corre- lations, and forbids system-environment back-action [12- 18]. This fact naturally leads to basic issues on the in- terpretation of back-action-free quantum revivals, in par- ticular about: (i) the role of a classical environment in reviving quantum correlations, for instance if it may act as a control system for what operation is applied to the qubits; (ii) the role of collective effects of the environ- ment on the qubits; (iii) the role of the memory effects; (iv) the role of possible system-environment correlations.In this presentation, I first make a brief overview of some theoretical results about revivals of entanglement in classical environments. I describe a model of two nonin- teracting qubits, initially entangled, where only one qubit is subject to a random external classical field (a laser with two random phases) with inhomogeneous broadening in its amplitude [18]. I then report the results of an all- optical experiment that simulates this model and allows us to observe and control revivals of quantum correlations without system-environment back-action [18]. Finally, Idiscuss about non-Markovianity and provide a possible interpretation showing the role of the classical environ- ment in this phenomenon.The findings so far reveal that the revivals of quantum correlations are a dynamical feature of composite open systems irrespective of the nature, classical or quantum, of the environment. These results introduce the possibil- ity to recover and control, against decoherence, quantum resources even in absence of back-action, without resort- ing to demanding quantum structured environments or quantum error correction procedures and open the way to further studies concerning quantum correlation dynamics in classical environments.[1] R. Horodecki, P. Horodecki, M. Horodecki, and K.Horodecki, Rev. Mod. Phys. 81, 865 (2009).[2] K. Modi, A. Brodutch, H. Cable, T. Paterek, and V.Vedral, Rev. Mod. Phys. 84, 1655 (2012).[3] T. Yu and J. H. Eberly, Science 323, 598 (2009).[4] J.-S. Xu et al., Nature Commun. 1, 7 (2010).[5] R. Lo Franco, B. Bellomo, S. Maniscalco, and G. Com-pagno, Int. J. Mod. Phys. B 27, 1345053 (2013).[6] J.-S. Xu et a

AB - Quantum correlations (entanglement, discord, nonlo-cality) present in a composite quantum system are essential resources for quantum information processing [1, 2]. However, the exploitation of these quantum resources is jeopardized by the detrimental effects of the environment surrounding the quantum system. For instance under Markovian noise, they decay asymptotically or disappear at a finite time [3, 4]. This drawback leads one to look for conditions where quantum correlations can be recovered during the evolution. To this aim non-Markovian noise, arising from strong couplings or structured environments, has been shown to be fundamental because of its memory effects. In fact, in the case of qubits in independent non-Markovian quantum environments, quantum corre- lations exhibit a combination of asymptotic decay with disappearance and revival [2, 5, 6], permitting their partial recovery and thus an extension of their use.Typically, for composite quantum systems within inde- pendent quantum environments, revivals of quantum cor- relations are interpreted as due to correlation exchanges induced by the back-action of non-Markovian quantum environments on the system (flows of quantum informa- tion back and forth from systems to quantum environments) [8-11]. Recently, it has been shown that revivals of quantum correlations may also occur when the envi- ronment is classical, thus unable to store quantum corre- lations, and forbids system-environment back-action [12- 18]. This fact naturally leads to basic issues on the in- terpretation of back-action-free quantum revivals, in par- ticular about: (i) the role of a classical environment in reviving quantum correlations, for instance if it may act as a control system for what operation is applied to the qubits; (ii) the role of collective effects of the environ- ment on the qubits; (iii) the role of the memory effects; (iv) the role of possible system-environment correlations.In this presentation, I first make a brief overview of some theoretical results about revivals of entanglement in classical environments. I describe a model of two nonin- teracting qubits, initially entangled, where only one qubit is subject to a random external classical field (a laser with two random phases) with inhomogeneous broadening in its amplitude [18]. I then report the results of an all- optical experiment that simulates this model and allows us to observe and control revivals of quantum correlations without system-environment back-action [18]. Finally, Idiscuss about non-Markovianity and provide a possible interpretation showing the role of the classical environ- ment in this phenomenon.The findings so far reveal that the revivals of quantum correlations are a dynamical feature of composite open systems irrespective of the nature, classical or quantum, of the environment. These results introduce the possibil- ity to recover and control, against decoherence, quantum resources even in absence of back-action, without resort- ing to demanding quantum structured environments or quantum error correction procedures and open the way to further studies concerning quantum correlation dynamics in classical environments.[1] R. Horodecki, P. Horodecki, M. Horodecki, and K.Horodecki, Rev. Mod. Phys. 81, 865 (2009).[2] K. Modi, A. Brodutch, H. Cable, T. Paterek, and V.Vedral, Rev. Mod. Phys. 84, 1655 (2012).[3] T. Yu and J. H. Eberly, Science 323, 598 (2009).[4] J.-S. Xu et al., Nature Commun. 1, 7 (2010).[5] R. Lo Franco, B. Bellomo, S. Maniscalco, and G. Com-pagno, Int. J. Mod. Phys. B 27, 1345053 (2013).[6] J.-S. Xu et a

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