A new quantum dynamic equation for excitation energy transfer is developed which can describe qua... more A new quantum dynamic equation for excitation energy transfer is developed which can describe quantum coherent wavelike motion and incoherent hopping in a unified manner. The developed equation reduces to the conventional Redfield theory and Förster theory in their respective limits of validity. In the regime of coherent wavelike motion, the equation predicts several times longer lifetime of electronic coherence between chromophores than does the conventional Redfield equation.
Starting from a system-bath Hamiltonian in a molecular coordinate representation, we examine an a... more Starting from a system-bath Hamiltonian in a molecular coordinate representation, we examine an applicability of a stochastic multilevel model for vibrational dephasing and energy relaxation in multidimensional infrared spectroscopy. We consider an intramolecular anharmonic mode nonlinearly coupled to a colored noise bath at finite temperature. The system-bath interaction is assumed linear plus square in the system coordinate, but linear in the bath coordinates.
The identification of parameters in the Hamiltonian that describes complex many-body quantum syste... more The identification of parameters in the Hamiltonian that describes complex many-body quantum systems is generally a very hard task. Recent attention has focused on such problems of Hamiltonian tomography for networks constructed with two-level systems. For open quantum systems, the fact that injected signals are likely to decay before they accumulate sufficient information for parameter estimation poses additional challenges.
Mounting experimental evidence for electronic quantum coherence in photosynthetic energy transfer... more Mounting experimental evidence for electronic quantum coherence in photosynthetic energy transfer [1–5] has spawned much debate about both the detailed nature and the biological role of such quantum dynamical features. Quantum coherence is usually encountered in the first, light-harvesting stage of photosynthesis. It includes two distinct but not mutually exclusive phenomena that can be differentiated by the choice of basis used to describe the electronic excitations.
accepted September 22, 2005) Reduced equations of motion for a two-level system strongly coupled ... more accepted September 22, 2005) Reduced equations of motion for a two-level system strongly coupled to a harmonic oscillators bath are constructed by extending the hierarchy of equations introduced by Tanimura and Kubo [J. Phys. Soc. Jpn. 58 (1989) 101]. The set of equations treats the bath in a nonperturbative manner and is applicable to a low-temperature system with taking into account the correlation time of noise.
Abstract We briefly review the coherent quantum beats observed in recent two-dimensional electron... more Abstract We briefly review the coherent quantum beats observed in recent two-dimensional electronic spectroscopy experiments in a photosynthetic-light-harvesting antenna. We emphasize that the decay of the quantum beats in these experiments is limited by ensemble averaging. The in vivo dynamics of energy transport depends upon the local fluctuations of a single photosynthetic complex during the energy transfer time (a few picoseconds).
In this CrystEngComm Hot article, Alicia Beatty and coworkers from the University of Missouri hav... more In this CrystEngComm Hot article, Alicia Beatty and coworkers from the University of Missouri have discovered that sterically demanding groups cause different hydrogen-bonding connectivity in certain lamellar solids. The group looked at 3, 5-pyrazole dicarboxylic acid and various amines and explored how this effected the packing of the co-crystals.
Abstract. We determine the real-time quantum dynamics of a biomolecular donor–acceptor system in ... more Abstract. We determine the real-time quantum dynamics of a biomolecular donor–acceptor system in order to describe excitonic energy transfer in the presence of slow environmental Gaussian fluctuations. For this, we compare two different approaches. On the one hand, we use the numerically exact iterative quasi-adiabatic propagator path-integral scheme that incorporates all non-Markovian contributions. On the other, we apply the second-order cumulant time-nonlocal quantum master equation that includes non-Markovian effects.
Reduced equation of motion for a multimode system coupled to multiple heat baths is constructed b... more Reduced equation of motion for a multimode system coupled to multiple heat baths is constructed by extending the quantum Fokker-Planck equation with low-temperature correction terms (J. Phys. Soc. Jpn. 2005, 74, 3131). Unlike such common approaches used to describe intramolecular multimode vibration as a Bloch-Redfield theory and a stochastic theory, the present formalism is defined by the molecular coordinates.
ABSTRACT: The observation of long-lived electronic quantum coherence in a photosynthetic light ha... more ABSTRACT: The observation of long-lived electronic quantum coherence in a photosynthetic light harvesting system [Engel et al. Nature 2007, 446, 782] has led to much effort being devoted to elucidation of the quantum mechanisms of the photosynthetic excitation energy transfer. In this paper we examine the question of whether the decay of the coherent beating signal is due to quantum mechanical decoherence or ensemble dephasing (also called “fake decoherence”).
The observation of long-lived electronic coherence in photosynthetic excitation energy transfer (... more The observation of long-lived electronic coherence in photosynthetic excitation energy transfer (EET) by Engel et al.[Nature (London)[bold 446], 782 (2007)] raises questions about the role of the protein environment in protecting this coherence and the significance of the quantum coherence in light harvesting efficiency. In this paper we explore the applicability of the Redfield equation in its full form, in the secular approximation and with neglect of the imaginary part of the relaxation terms for the study of these phenomena.
Based on the influence functional formalism, we have derived a nonperturbative equation of motion... more Based on the influence functional formalism, we have derived a nonperturbative equation of motion for a reduced system coupled to a harmonic bath with colored noise in which the system–bath coupling operator does not necessarily commute with the system Hamiltonian. The resultant expression coincides with the time-convolutionless quantum master equation derived from the second-order perturbative approximation, which is also equivalent to a generalized Redfield equation.
Simulating tunneling processes as well as their observation are challenging problems for many are... more Simulating tunneling processes as well as their observation are challenging problems for many areas. In this study, we consider a double-well potential system coupled to a heat bath with a linear-linear (LL) and square-linear (SL) system-bath interactions. The LL interaction leads to longitudinal and transversal homogeneous relaxations, whereas the SL interaction leads to the inhomogeneous dephasing relaxation in the white noise limit with a rotating wave approximation.
Light-harvesting components of photosynthetic organisms are complex, coupled, many-body quantum s... more Light-harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long timescales, despite the decohering effects of their environments. Here, we analyse entanglement in multichromophoric light-harvesting complexes, and establish methods for quantification of entanglement by describing necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement.
Recent two-dimensional (2D) electronic spectroscopic experiments revealed that electronic energy ... more Recent two-dimensional (2D) electronic spectroscopic experiments revealed that electronic energy transfer in photosynthetic light harvesting involves long-lived quantum coherence among electronic excitations of pigments. These findings have led to the suggestion that quantum coherence might play a role in achieving the remarkable quantum efficiency of photosynthetic light harvesting.
Abstract The observation of long-lived electronic coherence in a photosynthetic pigment–protein c... more Abstract The observation of long-lived electronic coherence in a photosynthetic pigment–protein complex, the Fenna–Matthews–Olson (FMO) complex, is suggestive that quantum coherence might play a significant role in achieving the remarkable efficiency of photosynthetic electronic energy transfer (EET), although the data were acquired at cryogenic temperature [Engel GS, et al.(2007) Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems. Nature 446: 782–786].
A new quantum dynamic equation for excitation energy transfer is developed which can describe qua... more A new quantum dynamic equation for excitation energy transfer is developed which can describe quantum coherent wavelike motion and incoherent hopping in a unified manner. The developed equation reduces to the conventional Redfield theory and Förster theory in their respective limits of validity. In the regime of coherent wavelike motion, the equation predicts several times longer lifetime of electronic coherence between chromophores than does the conventional Redfield equation.
Starting from a system-bath Hamiltonian in a molecular coordinate representation, we examine an a... more Starting from a system-bath Hamiltonian in a molecular coordinate representation, we examine an applicability of a stochastic multilevel model for vibrational dephasing and energy relaxation in multidimensional infrared spectroscopy. We consider an intramolecular anharmonic mode nonlinearly coupled to a colored noise bath at finite temperature. The system-bath interaction is assumed linear plus square in the system coordinate, but linear in the bath coordinates.
The identification of parameters in the Hamiltonian that describes complex many-body quantum syste... more The identification of parameters in the Hamiltonian that describes complex many-body quantum systems is generally a very hard task. Recent attention has focused on such problems of Hamiltonian tomography for networks constructed with two-level systems. For open quantum systems, the fact that injected signals are likely to decay before they accumulate sufficient information for parameter estimation poses additional challenges.
Mounting experimental evidence for electronic quantum coherence in photosynthetic energy transfer... more Mounting experimental evidence for electronic quantum coherence in photosynthetic energy transfer [1–5] has spawned much debate about both the detailed nature and the biological role of such quantum dynamical features. Quantum coherence is usually encountered in the first, light-harvesting stage of photosynthesis. It includes two distinct but not mutually exclusive phenomena that can be differentiated by the choice of basis used to describe the electronic excitations.
accepted September 22, 2005) Reduced equations of motion for a two-level system strongly coupled ... more accepted September 22, 2005) Reduced equations of motion for a two-level system strongly coupled to a harmonic oscillators bath are constructed by extending the hierarchy of equations introduced by Tanimura and Kubo [J. Phys. Soc. Jpn. 58 (1989) 101]. The set of equations treats the bath in a nonperturbative manner and is applicable to a low-temperature system with taking into account the correlation time of noise.
Abstract We briefly review the coherent quantum beats observed in recent two-dimensional electron... more Abstract We briefly review the coherent quantum beats observed in recent two-dimensional electronic spectroscopy experiments in a photosynthetic-light-harvesting antenna. We emphasize that the decay of the quantum beats in these experiments is limited by ensemble averaging. The in vivo dynamics of energy transport depends upon the local fluctuations of a single photosynthetic complex during the energy transfer time (a few picoseconds).
In this CrystEngComm Hot article, Alicia Beatty and coworkers from the University of Missouri hav... more In this CrystEngComm Hot article, Alicia Beatty and coworkers from the University of Missouri have discovered that sterically demanding groups cause different hydrogen-bonding connectivity in certain lamellar solids. The group looked at 3, 5-pyrazole dicarboxylic acid and various amines and explored how this effected the packing of the co-crystals.
Abstract. We determine the real-time quantum dynamics of a biomolecular donor–acceptor system in ... more Abstract. We determine the real-time quantum dynamics of a biomolecular donor–acceptor system in order to describe excitonic energy transfer in the presence of slow environmental Gaussian fluctuations. For this, we compare two different approaches. On the one hand, we use the numerically exact iterative quasi-adiabatic propagator path-integral scheme that incorporates all non-Markovian contributions. On the other, we apply the second-order cumulant time-nonlocal quantum master equation that includes non-Markovian effects.
Reduced equation of motion for a multimode system coupled to multiple heat baths is constructed b... more Reduced equation of motion for a multimode system coupled to multiple heat baths is constructed by extending the quantum Fokker-Planck equation with low-temperature correction terms (J. Phys. Soc. Jpn. 2005, 74, 3131). Unlike such common approaches used to describe intramolecular multimode vibration as a Bloch-Redfield theory and a stochastic theory, the present formalism is defined by the molecular coordinates.
ABSTRACT: The observation of long-lived electronic quantum coherence in a photosynthetic light ha... more ABSTRACT: The observation of long-lived electronic quantum coherence in a photosynthetic light harvesting system [Engel et al. Nature 2007, 446, 782] has led to much effort being devoted to elucidation of the quantum mechanisms of the photosynthetic excitation energy transfer. In this paper we examine the question of whether the decay of the coherent beating signal is due to quantum mechanical decoherence or ensemble dephasing (also called “fake decoherence”).
The observation of long-lived electronic coherence in photosynthetic excitation energy transfer (... more The observation of long-lived electronic coherence in photosynthetic excitation energy transfer (EET) by Engel et al.[Nature (London)[bold 446], 782 (2007)] raises questions about the role of the protein environment in protecting this coherence and the significance of the quantum coherence in light harvesting efficiency. In this paper we explore the applicability of the Redfield equation in its full form, in the secular approximation and with neglect of the imaginary part of the relaxation terms for the study of these phenomena.
Based on the influence functional formalism, we have derived a nonperturbative equation of motion... more Based on the influence functional formalism, we have derived a nonperturbative equation of motion for a reduced system coupled to a harmonic bath with colored noise in which the system–bath coupling operator does not necessarily commute with the system Hamiltonian. The resultant expression coincides with the time-convolutionless quantum master equation derived from the second-order perturbative approximation, which is also equivalent to a generalized Redfield equation.
Simulating tunneling processes as well as their observation are challenging problems for many are... more Simulating tunneling processes as well as their observation are challenging problems for many areas. In this study, we consider a double-well potential system coupled to a heat bath with a linear-linear (LL) and square-linear (SL) system-bath interactions. The LL interaction leads to longitudinal and transversal homogeneous relaxations, whereas the SL interaction leads to the inhomogeneous dephasing relaxation in the white noise limit with a rotating wave approximation.
Light-harvesting components of photosynthetic organisms are complex, coupled, many-body quantum s... more Light-harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long timescales, despite the decohering effects of their environments. Here, we analyse entanglement in multichromophoric light-harvesting complexes, and establish methods for quantification of entanglement by describing necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement.
Recent two-dimensional (2D) electronic spectroscopic experiments revealed that electronic energy ... more Recent two-dimensional (2D) electronic spectroscopic experiments revealed that electronic energy transfer in photosynthetic light harvesting involves long-lived quantum coherence among electronic excitations of pigments. These findings have led to the suggestion that quantum coherence might play a role in achieving the remarkable quantum efficiency of photosynthetic light harvesting.
Abstract The observation of long-lived electronic coherence in a photosynthetic pigment–protein c... more Abstract The observation of long-lived electronic coherence in a photosynthetic pigment–protein complex, the Fenna–Matthews–Olson (FMO) complex, is suggestive that quantum coherence might play a significant role in achieving the remarkable efficiency of photosynthetic electronic energy transfer (EET), although the data were acquired at cryogenic temperature [Engel GS, et al.(2007) Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems. Nature 446: 782–786].
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Papers by Akihito Ishizaki