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Coherent Transients in Semiconductor Nanostructures as the Base of Optical Logic Operating

I. Ya. Gerlovin, V. V. Ovsyankin, Boris V. Stroganov, Valerii S Zapasskii

Published Jun 23, 2000• 0 citations
OpenAlex

Abstract

The idea of the design is proposed for the photonic quantum gates (PG) with their input/output properties based on nonlinear optical dynamics of 2D arrays of two-level systems (TLS) in the resonance field of coherent optical pulses. As a particular example of the 2D medium with functions of the PG we consider the GaAs/AlGaAs-based 2D excitonic structures. By methods of femtosecond chronopolarimetry of delayed photoreflection. we have studied the energy and phase relaxation rates and the biexciton binding energy in these structures and have shown that the GaAs/AlGaAs MQW can serve as a good basis for building the PG.

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Coherent transients in semiconductor nanostructures as a basis for optical logical operations

I. Ya. Gerlovin, V. V. Ovsyankin, Boris V. Stroganov +1 more

We propose an approach to realization of all-optical logical operations based on the nonlinear dynamics of an ensemble of two-level systems (TLSs) in a coherent photonic field. Using a theoretical analysis of the behaviour of a TLS ensemble in a resonant field, we formulate requirements for dynamic characteristics of a medium suitable for implementation of a photonic gate. Experimental studies of optical dynamics and excitonic state spectra of epitaxial GaAs/AlGaAs quantum wells and superlattices has allowed us to conclude that their physical parameters make it possible to build photonic-gate matrices exceeding the transistor-based electronic switches in terms of their productive capacity by five to six orders of magnitude.

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Photon echoes from two-dimensional excitons in GaAs-AlGaAs quantum wells

Lothar Schultheis, Michael D. Sturge, John Hegarty

We report photon echoes from two-dimensional (2D) excitons in a GaAs-AlGaAs quantum well structure at 2 K. We analyze our data with a theoretical model of the generation of photon echoes by pulses of finite length which includes phase relaxation during excitation. A line shape analysis yields the phase relaxation time of 2D excitons. We find that the phase coherence near the line center decays, together with the resonant population, within 4 ps, whereas well below line center the phase coherence is conserved for times up to 20 ps.

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PHASE COHERENCE OF 2D EXCITONS IN GaAs-AlGaAs QUANTUM WELLS

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W. Langbein, Paola Borri, J. M. Hvam

The coherent response of excitons in semiconductor nanostructures measured in four-wave mixing (FWM) depends strongly on the inhomogeneous broadening of the exciton transition. We investigate GaAs/Al0.3Ga0.7As single quantum wells (SQW) and AlxGa1-xAs mixed crystals. Additional to the usual phase-space filling nonlinearity, excitation-induced dephasing (EID) and biexciton formation (BIF) are important. EID leads to a strong dependence of the signal on the angle between the linear input polarizations. We find that EID persists in inhomogeneous systems, showing that the mutual density-dependent dephasing rate difference between two subsystems within the inhomogeneous distribution is strongly dependent on their energy difference. BIF is strongly affecting the cross-linear polarized FWM response. The signal for positive delay is dominated by the transitions from the one-exciton state X to the two-exciton states. Here, the third-order polarization at X-XX is not at the same resonance as the first-order polarization at 0-X. Consequently, the rephasing of the microscopic third-order polarization to the macroscopic FWM photon echo is blurred by the non-perfect correlation of X and XX energies, leading to a fast and non-exponential signal decay in delay time. For inhomogeneous broadenings larger than the biexciton binding energy, we find an enhanced biexciton binding energy, and a quenching of the oscillator strength of the unbound biexciton.

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Resonant Secondary Emission from Two-Dimensional Excitons: Femtosecond Time Evolution of the Coherence Properties

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Physical Review Letters•Nov 9, 1998•71 citations

The two-qubit controlled-phase gate based on cross-phase modulation in GaAs/AlGaAs semiconductor quantum wells

Xiaoqing Luo, D. L. Wang, Hao Fan +1 more

We present a realization of two-qubit controlled-phase gate, based on the linear and nonlinear properties of the probe and signal optical pulses in an asymmetric GaAs/AlGaAs double quantum wells. It is shown that, in the presence of cross-phase modulation, a giant cross-Kerr nonlinearity and mutually matched group velocities of the probe and signal optical pulses can be achieved while realizing the suppression of linear and self-Kerr optical absorption synchronously. These characteristics serve to exhibit an all-optical two-qubit controlled-phase gate within efficiently controllable photon-photon entanglement by semiconductor mediation. In addition, by using just polarizing beam splitters and half-wave plates, we propose a practical experimental scheme to discriminate the maximally entangled polarization state of two-qubit through distinguishing two out of the four Bell states. This proposal potentially enables the realization of solid states mediated all-optical quantum computation and information processing.

arXiv:1201.3434•Jan 17, 2012•0 citations
The idea of the design is proposed for the photonic quantum gates (PG) with their input/output properties based on nonlinear optical dynamics of 2D arrays of two-level systems (TLS) in the resonance field of coherent optical pulses. As a particular example of the 2D medium with functions of the PG we consider the GaAs/AlGaAs-based 2D excitonic structures. By methods of femtosecond chronopolarimetry of delayed photoreflection. we have studied the energy and phase relaxation rates and the biexciton binding energy in these structures and have shown that the GaAs/AlGaAs MQW can serve as a good basis for building the PG.
We propose an approach to realization of all-optical logical operations based on the nonlinear dynamics of an ensemble of two-level systems (TLSs) in a coherent photonic field. Using a theoretical analysis of the behaviour of a TLS ensemble in a resonant field, we formulate requirements for dynamic characteristics of a medium suitable for implementation of a photonic gate. Experimental studies of optical dynamics and excitonic state spectra of epitaxial GaAs/AlGaAs quantum wells and superlattices has allowed us to conclude that their physical parameters make it possible to build photonic-gate matrices exceeding the transistor-based electronic switches in terms of their productive capacity by five to six orders of magnitude.
We report photon echoes from two-dimensional (2D) excitons in a GaAs-AlGaAs quantum well structure at 2 K. We analyze our data with a theoretical model of the generation of photon echoes by pulses of finite length which includes phase relaxation during excitation. A line shape analysis yields the phase relaxation time of 2D excitons. We find that the phase coherence near the line center decays, together with the resonant population, within 4 ps, whereas well below line center the phase coherence is conserved for times up to 20 ps.
The coherent response of excitons in semiconductor nanostructures measured in four-wave mixing (FWM) depends strongly on the inhomogeneous broadening of the exciton transition. We investigate GaAs/Al0.3Ga0.7As single quantum wells (SQW) and AlxGa1-xAs mixed crystals. Additional to the usual phase-space filling nonlinearity, excitation-induced dephasing (EID) and biexciton formation (BIF) are important. EID leads to a strong dependence of the signal on the angle between the linear input polarizations. We find that EID persists in inhomogeneous systems, showing that the mutual density-dependent dephasing rate difference between two subsystems within the inhomogeneous distribution is strongly dependent on their energy difference. BIF is strongly affecting the cross-linear polarized FWM response. The signal for positive delay is dominated by the transitions from the one-exciton state X to the two-exciton states. Here, the third-order polarization at X-XX is not at the same resonance as the first-order polarization at 0-X. Consequently, the rephasing of the microscopic third-order polarization to the macroscopic FWM photon echo is blurred by the non-perfect correlation of X and XX energies, leading to a fast and non-exponential signal decay in delay time. For inhomogeneous broadenings larger than the biexciton binding energy, we find an enhanced biexciton binding energy, and a quenching of the oscillator strength of the unbound biexciton.
Using a novel technique, we simultaneously study the femtosecond dynamics of the amplitude and the coherence of resonant secondary emission from GaAs quantum wells. Two phase-locked pulses resonantly excite excitons in the semiconductor and the subsequently emitted radiation is detected by femtosecond up-conversion. In experiments at various delays and phases between the excitation pulses we identify three different contributions to the secondary emission with different coherence properties in time.
We present a realization of two-qubit controlled-phase gate, based on the linear and nonlinear properties of the probe and signal optical pulses in an asymmetric GaAs/AlGaAs double quantum wells. It is shown that, in the presence of cross-phase modulation, a giant cross-Kerr nonlinearity and mutually matched group velocities of the probe and signal optical pulses can be achieved while realizing the suppression of linear and self-Kerr optical absorption synchronously. These characteristics serve to exhibit an all-optical two-qubit controlled-phase gate within efficiently controllable photon-photon entanglement by semiconductor mediation. In addition, by using just polarizing beam splitters and half-wave plates, we propose a practical experimental scheme to discriminate the maximally entangled polarization state of two-qubit through distinguishing two out of the four Bell states. This proposal potentially enables the realization of solid states mediated all-optical quantum computation and information processing.