E. Pazy - Academia.edu (original) (raw)
Papers by E. Pazy
Semiconductor Science and Technology, 2002
Pure dephasing of an exciton in a small quantum dot by optical and acoustic phonons is calculated... more Pure dephasing of an exciton in a small quantum dot by optical and acoustic phonons is calculated using the "independent boson model". Considering the case of zero temperature the dephasing is shown to be only partial which manifests itself in the polarization decaying to a finite value. Typical dephasing times can be assigned even though the spectra exhibits strongly non-Lorentzian line shapes. We show that the dephasing from LO phonon scattering, occurs on a much larger time scale than that of dephasing due to acoustic phonons which for low temperatures are also a more efficient dephasing mechanism. The typical dephasing time is shown to strongly depend on the quantum dot size whereas the electron phonon "coupling strength" and external electric fields tend mostly to effect the residual coherence. The relevance of the dephasing times for current quantum information processing implementation schemes in quantum dots is discussed.
Basics Physics and Quantum-Device Applications, 2005
We study the collective association dynamics of a cold Fermi gas of 2N atoms in M atomic modes in... more We study the collective association dynamics of a cold Fermi gas of 2N atoms in M atomic modes into a single molecular bosonic mode. The many-body fermionic problem for 2 M amplitudes is effectively reduced to a dynamical system of min{N, M } + 1 amplitudes, making the solution no more complex than the solution of a two-mode Bose-Einstein condensate and allowing realistic calculations with up to 10 4 particles. The many-body dynamics is shown to be formally similar to the dynamics of the bosonic system under the mapping of boson particles to fermion holes, producing collective enhancement effects due to many-particle constructive interference. Dissociation rates are shown to enhance as the number of particles whereas association rates are enhanced as the number of holes, leading to boson-like collective behavior.
Physical Review Letters, 2004
We explain why the experimental efficiency observed in the conversion of ultracold Fermi gases of... more We explain why the experimental efficiency observed in the conversion of ultracold Fermi gases of 40 K and 6 Li atoms into diatomic Bose gases is limited to 0.5 when the Feshbach resonance sweep rate is sufficiently slow to pass adiabatically through the Landau-Zener transition but faster than "the collision rate" in the gas, and increases beyond 0.5 when it is slower. The 0.5 efficiency limit is due to the preparation of a statistical mixture of two spin-states, required to enable s-wave scattering. By constructing the many-body state of the system we show that this preparation yields a mixture of even and odd parity pair-states, where only even parity can produce molecules. The odd parity spin-symmetric states must decorrelate before the constituent atoms can further Feshbach scatter thereby increasing the conversion efficiency; "the collision rate" is the pair decorrelation rate.
Physical Review Letters, 2005
We study the dynamics of an adiabatic sweep through a Feshbach resonance in a quantum gas of ferm... more We study the dynamics of an adiabatic sweep through a Feshbach resonance in a quantum gas of fermionic atoms. Analysis of the dynamical equations, supported by mean-field and many-body numerical results, shows that the dependence of the remaining atomic fraction Γ on the sweep rate α varies from exponential Landau-Zener behavior for a single pair of particles to a power-law dependence for large particle number N. The power-law is linear, Γ ∝ α, when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and Γ ∝ α 1/3 when it is larger. Experimental data agree better with a linear dependence than with an exponential Landau-Zener fit, indicating that many-body effects are significant in the atom-molecule conversion process.
Physical Review D, 2012
Employing a thermodynamic interpretation of gravity based on the holographic principle and assumi... more Employing a thermodynamic interpretation of gravity based on the holographic principle and assuming underlying particle statistics, fermionic or bosonic, for the excitations of the holographic screen leads to Modified Newtonian Dynamics (MOND). A connection between the acceleration scale a 0 appearing in MOND and the Fermi energy of the holographic fermionic degrees of freedom is obtained. In this formulation the physics of MOND results from the quantum-classical crossover in the fermionic specific heat. However, due to the dimensionality of the screen, the formalism is general and applies to two dimensional bosonic excitations as well. It is shown that replacing the assumption of the equipartition of energy on the holographic screen by a standard quantum-statistical-mechanics description wherein some of the degrees of freedom are frozen out at low temperatures is the physical basis for the MOND interpolating functionμ. The interpolating functionμ is calculated within the statistical mechanical formalism and compared to the leading phenomenological interpolating functions, most commonly used. Based on the statistical mechanical view of MOND, its cosmological implications are re-interpreted: the connection between a 0 and the Hubble constant is described as a quantum uncertainty relation; and the relationship between a 0 and the cosmological constant is better understood physically.
Physical Review B, 2005
As a candidate scheme for controllably coupled qubits, we consider two quantum dots, each doped w... more As a candidate scheme for controllably coupled qubits, we consider two quantum dots, each doped with a single electron. The spin of the electron defines our qubit basis and trion states can be created by using polarized light; we show that the form of the excited trion depends on the state of the qubit. By using the Luttinger-Kohn Hamiltonian we calculate the form of these trion states in the presence of light-heavy hole mixing, and show that they can interact through both the Förster transfer and static dipole-dipole interactions. Finally, we demonstrate that by using chirped laser pulses, it is possible to perform a two-qubit gate in this system by adiabatically following the eigenstates as a function of laser detuning. These gates are robust in that they operate with any realistic degree of hole mixing, and for either type of trion-trion coupling.
Physical Review A, 2006
We theoretically study the dynamics of an adiabatic sweep through a Feshbach resonance, thereby c... more We theoretically study the dynamics of an adiabatic sweep through a Feshbach resonance, thereby converting a degenerate quantum gas of fermionic atoms into a degenerate quantum gas of bosonic dimers. Our analysis relies on a zero-temperature mean-field theory which accurately accounts for initial molecular quantum fluctuations, triggering the association process. The structure of the resulting semiclassical phase-space is investigated, highlighting the dynamical instability of the system towards association, for sufficiently small detuning from resonance. It is shown that this instability significantly modifies the finite-rate efficiency of the sweep, transforming the single-pair exponential LZ behavior of the remnent fraction of atoms Γ on sweep rate α, into a a power law dependence as the number of atoms increases. The obtained nonadiabaticity is determined from the interplay of characteristic timescales for the motion of adiabatic eigenstates and for fast periodic motion around them. Critical slowing-down of these precessions near the instability, leads to the power-law dependence. A Linear power-law Γ ∝ α, is obtained when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and a cubic-root power-law Γ ∝ α 1/3 is attained when it is larger. Our mean-field analysis is confirmed by exact calculations, using Fock-space expansions. Finally, we fit experimental low temperature Feshbach sweep data with a power-law dependence. While the agreement with the experimental data is well within experimental error bars, similar accuracy can be obtained with an exponential fit, making additional data highly desirable.
Physical Review A, 2008
Pair operators for boson and fermion atoms generate SU͑1,1͒ and SU͑2͒ Lie algebras, respectively.... more Pair operators for boson and fermion atoms generate SU͑1,1͒ and SU͑2͒ Lie algebras, respectively. Consequently, the pairing of boson and fermion atoms into diatomic molecules via Feshbach resonances, produces SU͑1,1͒ and SU͑2͒ coherent states, making bosonic pairing the matter-wave equivalent of parametric coupling and fermion pairing equivalent to the Dicke model of quantum optics. We discuss the properties of atomic states generated in the dissociation of molecular Bose-Einstein condensates into boson or fermion constituent atoms. The SU͑2͒ coherent states produced in dissociation into fermions give Poissonian atom-number distributions, whereas the SU͑1,1͒ states generated in dissociation into bosons result in super-Poissonian distributions, in analogy to two-photon squeezed states. In contrast, starting from an atomic gas produces coherent number distributions for bosons and super-Poissonian distributions for fermions.
Physical Review A, 2005
We study an ultracold bose-fermi mixture in a one dimensional optical lattice. When boson atoms a... more We study an ultracold bose-fermi mixture in a one dimensional optical lattice. When boson atoms are heavier then fermion atoms the system is described by an adiabatic Holstein model, exhibiting a Peierls instability for commensurate fermion filling factors. A Bosonic density wave with a wavenumber of twice the Fermi wavenumber will appear in the quasi one-dimensional system.
physica status solidi (b), 2003
ABSTRACT An all-optical implementation scheme of a spin-based quantum computer is presented. Our ... more ABSTRACT An all-optical implementation scheme of a spin-based quantum computer is presented. Our quantum memory consists of the spin of electrons confined to quantum dots. Utilizing the Pauli blocking effect we are able to have ultra-fast control and read out of the electronic spin degrees of freedom by conditionally coupling them with charged excitations of the quantum dot. Imperfections effecting gate operations are discussed and we show that final readout can still be performed by a quantum-jump technique even in the presence of hole mixing, when the Pauli-blocking selection rule is violated.
physica status solidi (b), 2004
ABSTRACT Using numerical simulations we studied the long-time relaxation of the hopping conductiv... more ABSTRACT Using numerical simulations we studied the long-time relaxation of the hopping conductivity. We perturbed the system through insertion of electrons and monitored the conductivity as a function of time. Even though employing numerical simulations one can only follow the system for very short time scales we have shown that during such available times we can reach an apparent saturation of conductivity and energy. In order to investigate the long-time relaxation of the system we studied the difference between the saturated values of the conductivities obtained by the short-time relaxation from initial excited states with different electron distribution. We have related these two typical time scales to relaxation in one pseudoground state and to very slow transitions between pseudoground states. By employing two different two-dimensional models with electron–electron interactions we were able to show the effect of disorder on the relaxation of conductivity. In the strong-disorder case the universality of the Coulomb gap, which is responsible for the universal Efros–Shklovskii law for the conductivity, suppresses the long-time relaxation of conductivity since the universality strongly decreases the dispersion of conductivities of the pseudoground states. In the second model with a weak external disorder we found a difference between saturated values of conductivity in agreement with the experimental data. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (a), 2002
A review of semiconductor-based schemes for the implementation of quantum information processing ... more A review of semiconductor-based schemes for the implementation of quantum information processing devices is presented. After recalling the fundamentals of quantum information/computation theory, we shall discuss two potential implementation schemes based on charge degrees of freedom in semiconductor nanostructures. More specifically, we shall present an all-optical implementation of quantum information processing with semiconductor macroatoms/molecules. In this case the computational degrees of freedom are interband optical transitions driven by ultrafast sequences of multicolor laser-pulse trains. As alternative approach, we shall also discuss a transportlike scheme based on ballistic electrons in coupled semiconductor quantum wires. Within such implementation strategy, we shall finally propose a relatively simple quantum gating sequence for testing Bell inequality violations in a condensed-matter environment.
Physica B: Condensed Matter, 2002
We present a measurement scheme designed to measure the state of an exciton in a single quantum d... more We present a measurement scheme designed to measure the state of an exciton in a single quantum dot: the measurement is performed by employing the stimulated Raman adiabatic passage and its result is stored in a double quantum dot structure. Calculations showing that the requirements for acting as a measurement device are fulfilled by the proposed semiconductor nanostructure are presented.
Physica B: Condensed Matter, 2002
We shall review two implementation proposals for quantum information processing based on charge d... more We shall review two implementation proposals for quantum information processing based on charge degrees-offreedom in semiconductor nanostructures. An all-optical implementation scheme using semiconductor macroatoms/ molecules will be discussed. The computational degrees-of-freedom in this proposal are interband optical transitions driven by ultrafast sequences of multicolor laser-pulse trains. The conditional dynamics necessary for universal quantum computation is provided by exciton-exciton coupling between different quantum dots in an array. We shall also discuss an alternative scheme based on transport of ballistic electrons in coupled semiconductor quantum wires. In the framework of such implementation strategy, we shall finally discuss a potential simple way for testing violation of Bell's inequality in a condensed-matter setting.
Journal of Modern Optics, 2007
ABSTRACT The dynamics of an adiabatic sweep through a Feshbach resonance in a degenerate quantum ... more ABSTRACT The dynamics of an adiabatic sweep through a Feshbach resonance in a degenerate quantum gas of fermionic atoms to produce a degenerate quantum gas of diatomic molecules are studied using many-body and mean-field methods. We demonstrate that the dependence of the remaining fraction of atoms Γ on sweep rate α varies from exponential Landau–Zener behaviour for a single pair of particles, to a power-law dependence for a large number of atoms, N. Two different power-law behaviours are obtained depending on the initial molecular fraction. The two different regimes are described in terms of quantum fluctuations: a linear power-law, Γ∝α, is obtained when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and Γ∝α when it is larger.
IEEE Transactions On Nanotechnology, 2004
... of the ideas and concepts discussed in this review article, and E. Biolatti, I. D'Amico,... more ... of the ideas and concepts discussed in this review article, and E. Biolatti, I. D'Amico, S. De Rinaldis, RC Iotti, and E. Pazy as well as T. Calarco and P. Zoller for relevant contributions to the research activity reviewed in the paper. He would also like to thank D. Di-Vincenzo and S ...
IEEE Transactions On Nanotechnology, 2004
Utilizing the Pauli-blocking mechanism we show that shining circular polarized light on a singly ... more Utilizing the Pauli-blocking mechanism we show that shining circular polarized light on a singly charged quantum dot induces spin dependent fluorescence. Employing the quantum-jump technique we demonstrate that this resonance luminescence, due to a spin dependent optical excitation, serves as an excellent read out mechanism for measuring the spin state of a single electron confined to a quantum dot.
Europhysics Letters (EPL), 2004
Nonlinear photocurrent carriers in conjugated polymers, such as polarons, bipolarons and solitons... more Nonlinear photocurrent carriers in conjugated polymers, such as polarons, bipolarons and solitons, are considered at low photon energies where a tunnelling process is necessary. We show that polarons usually dominate the photocurrent I due to a novel electric field assisted tunnelling for which ln I ∼ −E −2/3. For near degenerate polymers an electric field E which exceeds the confinement potential and frequencies above twice the soliton energy, soliton tunnelling is favored. Photocurrent data can then be used to identify the remarkable phenomenon of soliton conduction.
Semiconductor Science and Technology, 2002
Pure dephasing of an exciton in a small quantum dot by optical and acoustic phonons is calculated... more Pure dephasing of an exciton in a small quantum dot by optical and acoustic phonons is calculated using the "independent boson model". Considering the case of zero temperature the dephasing is shown to be only partial which manifests itself in the polarization decaying to a finite value. Typical dephasing times can be assigned even though the spectra exhibits strongly non-Lorentzian line shapes. We show that the dephasing from LO phonon scattering, occurs on a much larger time scale than that of dephasing due to acoustic phonons which for low temperatures are also a more efficient dephasing mechanism. The typical dephasing time is shown to strongly depend on the quantum dot size whereas the electron phonon "coupling strength" and external electric fields tend mostly to effect the residual coherence. The relevance of the dephasing times for current quantum information processing implementation schemes in quantum dots is discussed.
Basics Physics and Quantum-Device Applications, 2005
We study the collective association dynamics of a cold Fermi gas of 2N atoms in M atomic modes in... more We study the collective association dynamics of a cold Fermi gas of 2N atoms in M atomic modes into a single molecular bosonic mode. The many-body fermionic problem for 2 M amplitudes is effectively reduced to a dynamical system of min{N, M } + 1 amplitudes, making the solution no more complex than the solution of a two-mode Bose-Einstein condensate and allowing realistic calculations with up to 10 4 particles. The many-body dynamics is shown to be formally similar to the dynamics of the bosonic system under the mapping of boson particles to fermion holes, producing collective enhancement effects due to many-particle constructive interference. Dissociation rates are shown to enhance as the number of particles whereas association rates are enhanced as the number of holes, leading to boson-like collective behavior.
Physical Review Letters, 2004
We explain why the experimental efficiency observed in the conversion of ultracold Fermi gases of... more We explain why the experimental efficiency observed in the conversion of ultracold Fermi gases of 40 K and 6 Li atoms into diatomic Bose gases is limited to 0.5 when the Feshbach resonance sweep rate is sufficiently slow to pass adiabatically through the Landau-Zener transition but faster than "the collision rate" in the gas, and increases beyond 0.5 when it is slower. The 0.5 efficiency limit is due to the preparation of a statistical mixture of two spin-states, required to enable s-wave scattering. By constructing the many-body state of the system we show that this preparation yields a mixture of even and odd parity pair-states, where only even parity can produce molecules. The odd parity spin-symmetric states must decorrelate before the constituent atoms can further Feshbach scatter thereby increasing the conversion efficiency; "the collision rate" is the pair decorrelation rate.
Physical Review Letters, 2005
We study the dynamics of an adiabatic sweep through a Feshbach resonance in a quantum gas of ferm... more We study the dynamics of an adiabatic sweep through a Feshbach resonance in a quantum gas of fermionic atoms. Analysis of the dynamical equations, supported by mean-field and many-body numerical results, shows that the dependence of the remaining atomic fraction Γ on the sweep rate α varies from exponential Landau-Zener behavior for a single pair of particles to a power-law dependence for large particle number N. The power-law is linear, Γ ∝ α, when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and Γ ∝ α 1/3 when it is larger. Experimental data agree better with a linear dependence than with an exponential Landau-Zener fit, indicating that many-body effects are significant in the atom-molecule conversion process.
Physical Review D, 2012
Employing a thermodynamic interpretation of gravity based on the holographic principle and assumi... more Employing a thermodynamic interpretation of gravity based on the holographic principle and assuming underlying particle statistics, fermionic or bosonic, for the excitations of the holographic screen leads to Modified Newtonian Dynamics (MOND). A connection between the acceleration scale a 0 appearing in MOND and the Fermi energy of the holographic fermionic degrees of freedom is obtained. In this formulation the physics of MOND results from the quantum-classical crossover in the fermionic specific heat. However, due to the dimensionality of the screen, the formalism is general and applies to two dimensional bosonic excitations as well. It is shown that replacing the assumption of the equipartition of energy on the holographic screen by a standard quantum-statistical-mechanics description wherein some of the degrees of freedom are frozen out at low temperatures is the physical basis for the MOND interpolating functionμ. The interpolating functionμ is calculated within the statistical mechanical formalism and compared to the leading phenomenological interpolating functions, most commonly used. Based on the statistical mechanical view of MOND, its cosmological implications are re-interpreted: the connection between a 0 and the Hubble constant is described as a quantum uncertainty relation; and the relationship between a 0 and the cosmological constant is better understood physically.
Physical Review B, 2005
As a candidate scheme for controllably coupled qubits, we consider two quantum dots, each doped w... more As a candidate scheme for controllably coupled qubits, we consider two quantum dots, each doped with a single electron. The spin of the electron defines our qubit basis and trion states can be created by using polarized light; we show that the form of the excited trion depends on the state of the qubit. By using the Luttinger-Kohn Hamiltonian we calculate the form of these trion states in the presence of light-heavy hole mixing, and show that they can interact through both the Förster transfer and static dipole-dipole interactions. Finally, we demonstrate that by using chirped laser pulses, it is possible to perform a two-qubit gate in this system by adiabatically following the eigenstates as a function of laser detuning. These gates are robust in that they operate with any realistic degree of hole mixing, and for either type of trion-trion coupling.
Physical Review A, 2006
We theoretically study the dynamics of an adiabatic sweep through a Feshbach resonance, thereby c... more We theoretically study the dynamics of an adiabatic sweep through a Feshbach resonance, thereby converting a degenerate quantum gas of fermionic atoms into a degenerate quantum gas of bosonic dimers. Our analysis relies on a zero-temperature mean-field theory which accurately accounts for initial molecular quantum fluctuations, triggering the association process. The structure of the resulting semiclassical phase-space is investigated, highlighting the dynamical instability of the system towards association, for sufficiently small detuning from resonance. It is shown that this instability significantly modifies the finite-rate efficiency of the sweep, transforming the single-pair exponential LZ behavior of the remnent fraction of atoms Γ on sweep rate α, into a a power law dependence as the number of atoms increases. The obtained nonadiabaticity is determined from the interplay of characteristic timescales for the motion of adiabatic eigenstates and for fast periodic motion around them. Critical slowing-down of these precessions near the instability, leads to the power-law dependence. A Linear power-law Γ ∝ α, is obtained when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and a cubic-root power-law Γ ∝ α 1/3 is attained when it is larger. Our mean-field analysis is confirmed by exact calculations, using Fock-space expansions. Finally, we fit experimental low temperature Feshbach sweep data with a power-law dependence. While the agreement with the experimental data is well within experimental error bars, similar accuracy can be obtained with an exponential fit, making additional data highly desirable.
Physical Review A, 2008
Pair operators for boson and fermion atoms generate SU͑1,1͒ and SU͑2͒ Lie algebras, respectively.... more Pair operators for boson and fermion atoms generate SU͑1,1͒ and SU͑2͒ Lie algebras, respectively. Consequently, the pairing of boson and fermion atoms into diatomic molecules via Feshbach resonances, produces SU͑1,1͒ and SU͑2͒ coherent states, making bosonic pairing the matter-wave equivalent of parametric coupling and fermion pairing equivalent to the Dicke model of quantum optics. We discuss the properties of atomic states generated in the dissociation of molecular Bose-Einstein condensates into boson or fermion constituent atoms. The SU͑2͒ coherent states produced in dissociation into fermions give Poissonian atom-number distributions, whereas the SU͑1,1͒ states generated in dissociation into bosons result in super-Poissonian distributions, in analogy to two-photon squeezed states. In contrast, starting from an atomic gas produces coherent number distributions for bosons and super-Poissonian distributions for fermions.
Physical Review A, 2005
We study an ultracold bose-fermi mixture in a one dimensional optical lattice. When boson atoms a... more We study an ultracold bose-fermi mixture in a one dimensional optical lattice. When boson atoms are heavier then fermion atoms the system is described by an adiabatic Holstein model, exhibiting a Peierls instability for commensurate fermion filling factors. A Bosonic density wave with a wavenumber of twice the Fermi wavenumber will appear in the quasi one-dimensional system.
physica status solidi (b), 2003
ABSTRACT An all-optical implementation scheme of a spin-based quantum computer is presented. Our ... more ABSTRACT An all-optical implementation scheme of a spin-based quantum computer is presented. Our quantum memory consists of the spin of electrons confined to quantum dots. Utilizing the Pauli blocking effect we are able to have ultra-fast control and read out of the electronic spin degrees of freedom by conditionally coupling them with charged excitations of the quantum dot. Imperfections effecting gate operations are discussed and we show that final readout can still be performed by a quantum-jump technique even in the presence of hole mixing, when the Pauli-blocking selection rule is violated.
physica status solidi (b), 2004
ABSTRACT Using numerical simulations we studied the long-time relaxation of the hopping conductiv... more ABSTRACT Using numerical simulations we studied the long-time relaxation of the hopping conductivity. We perturbed the system through insertion of electrons and monitored the conductivity as a function of time. Even though employing numerical simulations one can only follow the system for very short time scales we have shown that during such available times we can reach an apparent saturation of conductivity and energy. In order to investigate the long-time relaxation of the system we studied the difference between the saturated values of the conductivities obtained by the short-time relaxation from initial excited states with different electron distribution. We have related these two typical time scales to relaxation in one pseudoground state and to very slow transitions between pseudoground states. By employing two different two-dimensional models with electron–electron interactions we were able to show the effect of disorder on the relaxation of conductivity. In the strong-disorder case the universality of the Coulomb gap, which is responsible for the universal Efros–Shklovskii law for the conductivity, suppresses the long-time relaxation of conductivity since the universality strongly decreases the dispersion of conductivities of the pseudoground states. In the second model with a weak external disorder we found a difference between saturated values of conductivity in agreement with the experimental data. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (a), 2002
A review of semiconductor-based schemes for the implementation of quantum information processing ... more A review of semiconductor-based schemes for the implementation of quantum information processing devices is presented. After recalling the fundamentals of quantum information/computation theory, we shall discuss two potential implementation schemes based on charge degrees of freedom in semiconductor nanostructures. More specifically, we shall present an all-optical implementation of quantum information processing with semiconductor macroatoms/molecules. In this case the computational degrees of freedom are interband optical transitions driven by ultrafast sequences of multicolor laser-pulse trains. As alternative approach, we shall also discuss a transportlike scheme based on ballistic electrons in coupled semiconductor quantum wires. Within such implementation strategy, we shall finally propose a relatively simple quantum gating sequence for testing Bell inequality violations in a condensed-matter environment.
Physica B: Condensed Matter, 2002
We present a measurement scheme designed to measure the state of an exciton in a single quantum d... more We present a measurement scheme designed to measure the state of an exciton in a single quantum dot: the measurement is performed by employing the stimulated Raman adiabatic passage and its result is stored in a double quantum dot structure. Calculations showing that the requirements for acting as a measurement device are fulfilled by the proposed semiconductor nanostructure are presented.
Physica B: Condensed Matter, 2002
We shall review two implementation proposals for quantum information processing based on charge d... more We shall review two implementation proposals for quantum information processing based on charge degrees-offreedom in semiconductor nanostructures. An all-optical implementation scheme using semiconductor macroatoms/ molecules will be discussed. The computational degrees-of-freedom in this proposal are interband optical transitions driven by ultrafast sequences of multicolor laser-pulse trains. The conditional dynamics necessary for universal quantum computation is provided by exciton-exciton coupling between different quantum dots in an array. We shall also discuss an alternative scheme based on transport of ballistic electrons in coupled semiconductor quantum wires. In the framework of such implementation strategy, we shall finally discuss a potential simple way for testing violation of Bell's inequality in a condensed-matter setting.
Journal of Modern Optics, 2007
ABSTRACT The dynamics of an adiabatic sweep through a Feshbach resonance in a degenerate quantum ... more ABSTRACT The dynamics of an adiabatic sweep through a Feshbach resonance in a degenerate quantum gas of fermionic atoms to produce a degenerate quantum gas of diatomic molecules are studied using many-body and mean-field methods. We demonstrate that the dependence of the remaining fraction of atoms Γ on sweep rate α varies from exponential Landau–Zener behaviour for a single pair of particles, to a power-law dependence for a large number of atoms, N. Two different power-law behaviours are obtained depending on the initial molecular fraction. The two different regimes are described in terms of quantum fluctuations: a linear power-law, Γ∝α, is obtained when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and Γ∝α when it is larger.
IEEE Transactions On Nanotechnology, 2004
... of the ideas and concepts discussed in this review article, and E. Biolatti, I. D'Amico,... more ... of the ideas and concepts discussed in this review article, and E. Biolatti, I. D'Amico, S. De Rinaldis, RC Iotti, and E. Pazy as well as T. Calarco and P. Zoller for relevant contributions to the research activity reviewed in the paper. He would also like to thank D. Di-Vincenzo and S ...
IEEE Transactions On Nanotechnology, 2004
Utilizing the Pauli-blocking mechanism we show that shining circular polarized light on a singly ... more Utilizing the Pauli-blocking mechanism we show that shining circular polarized light on a singly charged quantum dot induces spin dependent fluorescence. Employing the quantum-jump technique we demonstrate that this resonance luminescence, due to a spin dependent optical excitation, serves as an excellent read out mechanism for measuring the spin state of a single electron confined to a quantum dot.
Europhysics Letters (EPL), 2004
Nonlinear photocurrent carriers in conjugated polymers, such as polarons, bipolarons and solitons... more Nonlinear photocurrent carriers in conjugated polymers, such as polarons, bipolarons and solitons, are considered at low photon energies where a tunnelling process is necessary. We show that polarons usually dominate the photocurrent I due to a novel electric field assisted tunnelling for which ln I ∼ −E −2/3. For near degenerate polymers an electric field E which exceeds the confinement potential and frequencies above twice the soliton energy, soliton tunnelling is favored. Photocurrent data can then be used to identify the remarkable phenomenon of soliton conduction.