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M. Combescot M.-A. Dupertuis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):459-464
We show that the carrier “antibinding” observed recently in
semiconductor quantum dots, i.e., the fact that the ground state
energy of two electron-hole pairs goes above twice the ground-state
energy of one pair, can entirely be assigned to a charge separation
effect, whatever its origin. In the absence of external electric field, this charge
separation comes from different “spreading-out” of the electron and
hole wavefunctions linked to the finite height of the barriers. When
the dot size shrinks, the two-pair energy always stays below when the
barriers are infinite. On the opposite, because barriers are less
efficient for small dots, the energy of two-pairs in a dot with
finite barriers, ends by behaving like the one in bulk, i.e., by
going above twice the one-pair energy when the pairs get too close.
For a full understanding of this “antibinding” effect, we have also
reconsidered the case of one pair plus one carrier. We find that,
while the carriers just have to spread out of the dot differently for
the “antibinding” of two-pairs to appear, this “antibinding” for
one pair plus one carrier only appears if this carrier is the one
which spreads out the less. In addition a remarkable sum rule exists
between the “binding energies” of two pairs and of one pair plus one carrier. 相似文献
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Dupertuis MA Karlsson KF Oberli DY Pelucchi E Rudra A Holtz PO Kapon E 《Physical review letters》2011,107(12):127403
A systematic and simple theoretical approach is proposed to analyze true degeneracies and polarized decay patterns of exciton complexes in semiconductor quantum dots. The results provide reliable spectral signatures for efficient symmetry characterization, and predict original features for low C(2v) and high C(3v) symmetries. Excellent agreement with single quantum dot spectroscopy of real pyramidal InGaAs/AlGaAs quantum dots grown along [111] is demonstrated. The high sensitivity of biexciton quantum states to exact high symmetry can be turned into an efficient uninvasive postgrowth selection procedure for quantum entanglement applications. 相似文献
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Elias Riedel Grding Nicolas Schwaller Chun Lam Chan Su Yeon Chang Samuel Bosch Frederic Gessler Willy Robert Laborde Javier Naya Hernandez Xinyu Si Marc-Andr Dupertuis Nicolas Macris 《Entropy (Basel, Switzerland)》2021,23(7)
We propose the first correct special-purpose quantum circuits for preparation of Bell diagonal states (BDS), and implement them on the IBM Quantum computer, characterizing and testing complex aspects of their quantum correlations in the full parameter space. Among the circuits proposed, one involves only two quantum bits but requires adapted quantum tomography routines handling classical bits in parallel. The entire class of Bell diagonal states is generated, and several characteristic indicators, namely entanglement of formation and concurrence, CHSH non-locality, steering and discord, are experimentally evaluated over the full parameter space and compared with theory. As a by-product of this work, we also find a remarkable general inequality between “quantum discord” and “asymmetric relative entropy of discord”: the former never exceeds the latter. We also prove that for all BDS the two coincide. 相似文献
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The properties of V-shaped optical dielectric waveguides are investigated in detail using a vectorial finite element method. The fundamental modes exhibit extremely tight, heart shaped near field patterns. The maximum intensity of the fundamental mode is found to be vertically shifted with respect to the geometrical center of the waveguide. Fundamental and higher order mode properties are extensively studied, including mode patterns, dispersion curves and polarization properties. The local mode polarization of the two fundamental modes varies from a horizontal (vertical) orientation at the groove center to TM (or TE respectively) far in the side wings. The optimal design of waveguides for GaAs/AlGaAs quantum wire diode lasers and Quantum Confined Stark Effect modulators grown on V-grooved substrates is discussed. 相似文献
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R. Behn M. A. Dupertuis I. Kjelberg P. D. Morgan T. Okada M. R. Siegrist B. Couillaud A. Ducasse E. Freysz L. Sarger Lu Yia Xiong E. Fischer Z. N. Rozkwitalski F. K. Kneubühl J. S. Helman C. Rau C. F. Bunge A. K. Kar R. G. Harrison C. A. Emshary D. M. Tratt S. D. Smith G. Marowsky E. Albers K. Hohla W. T. Silfvast O. R. Wood II J. J. Macklin K. -H. Stephan-Rossbach F. J. Comes F. K. Tittel R. Sauerbrey W. Walter W. L. Wilson Jr. 《Applied physics. B, Lasers and optics》1982,29(3):143-148
Conclusion We have demonstrated the existence of an anomalous polarization coupling mechanism present in the injection locked TEA CO2 laser. As a direct consequence of this work, a new injection technique has been formulated which permits efficient injection coupling and maximises energy extraction whilst eliminating the detrimental optical feedback effects to which other injection locking systems are prone.Supported by the Office of Naval Research and the National Science Foundation 相似文献
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Competition between Raman and line-centre oscillation in multilevel lasers pumped with coherent radiation off resonance is studied by means of semi-classical laser theory. In a four level system consisting of a combination of a Λ and V system, it is shown that simultaneous Raman and line centre oscillation is expected on one of the transitions contrary to the case of a simple three level system where the Raman line completely suppresses the line centre oscillation. The crucial importance of a new highly nonlinear phase locking effect for the behaviour of the system is demonstrated. 相似文献
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A fully two-dimensional study of the electronic sub-bands in crescent-shaped quantum wires is presented. The confinement energies and the wave functions are compared by means of an aspect ratio to those produced by the adiabatic approximation. Guidelines for applying the adiabatic model are provided and the adiabatic quantum number classification scheme is discussed. Non- adiabatic states are determined among the first few sub-bands and a built-in dipole is identified. The energy spectrum is explored as a function of wire dimensions achievable by present-day technology. Wire parameters corresponding to maximized sub-band separations are determined. 相似文献
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