The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Yuval Gefen - One of the best experts on this subject based on the ideXlab platform.
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Weak-measurement-induced asymmetric Dephasing: a topological transition.
arXiv: Quantum Physics, 2020Co-Authors: Kyrylo Snizhko, Parveen Kumar, Nihal Rao, Yuval GefenAbstract:Geometrical Dephasing is distinct from dynamical Dephasing in that it depends on the trajectory traversed, hence it reverses its sign upon flipping the direction in which the path is traced. Here we study sequences of generalized (weak) measurements that steer a system in a closed trajectory. The readout process is marked by fluctuations, giving rise to Dephasing. The latter comprises a contribution which is invariant under reversal of the sequence ordering, and, in analogy with geometrical Dephasing, one which flips its sign upon reversal of the winding direction, which may result in "coherency enhancement". This asymmetric Dephasing diverges at certain protocol parameters, marking topological transitions in the measurement-induced phase factor.
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Measurement of geometric Dephasing using a superconducting qubit.
Nature communications, 2015Co-Authors: Simon A. Berger, Yuval Gefen, Alexander Shnirman, Marek Pechal, Philipp Kurpiers, A. A. Abdumalikov, Christopher Eichler, J. A. Mlynek, Andreas Wallraff, Stefan FilippAbstract:A quantum system interacting with its environment is subject to Dephasing, which ultimately destroys the information it holds. Here we use a superconducting qubit to experimentally show that this Dephasing has both dynamic and geometric origins. It is found that geometric Dephasing, which is present even in the adiabatic limit and when no geometric phase is acquired, can either reduce or restore coherence depending on the orientation of the path the qubit traces out in its projective Hilbert space. It accompanies the evolution of any system in Hilbert space subjected to noise.
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Dephasing by a zero-temperature detector and the Friedel sum rule.
Physical review letters, 2012Co-Authors: Bernd Rosenow, Yuval GefenAbstract:Detecting the passage of an interfering particle through one of the interferometer's arms, known as "which path" measurement, gives rise to interference visibility degradation (Dephasing). Here, we consider a detector at equilibrium. At finite temperature, Dephasing is caused by thermal fluctuations of the detector. More interestingly, in the zero-temperature limit, equilibrium quantum fluctuations of the detector give rise to Dephasing of the out-of-equilibrium interferometer. This Dephasing is a manifestation of an orthogonality catastrophe, which differs qualitatively from Anderson's. Its magnitude is directly related to the Friedel sum rule.
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Towards a Dephasing diode: asymmetric and geometric Dephasing.
Physical review letters, 2008Co-Authors: Robert S. Whitney, Alexander Shnirman, Yuval GefenAbstract:We study the effect of a noisy environment on spin and charge transport in ballistic quantum wires with spin-orbit coupling (Rashba coupling). We find that the wire then acts as a Dephasing diode, inducing very different Dephasing of the spins of right and left movers. We also show how Berry phase (geometric phase) in a curved wire can induce such asymmetric Dephasing, in addition to purely geometric Dephasing. We propose ways to measure these effects through spin detectors, spin-echo techniques, and Aharanov-Bohm interferometry.
S R Clark - One of the best experts on this subject based on the ideXlab platform.
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Dephasing enhanced spin transport in the ergodic phase of a many body localizable system
Annalen der Physik, 2017Co-Authors: Marko žnidaric, J J Mendozaarenas, S R Clark, John GooldAbstract:We study high temperature spin transport in a disordered Heisenberg chain in the ergodic regime when bulk Dephasing is present. We find that while Dephasing always renders the transport diffusive, there is nonetheless a remnant of the diffusive to sub-diffusive transition found in a system without Dephasing manifested in the behaviour of the diffusion constant with the Dephasing strength. By studying finite-size effects we show numerically and theoretically that this feature is caused by the competition between large crossover length scales associated to disorder and Dephasing that control the dynamics observed in the thermodynamic limit. We demonstrate that this competition may lead to a Dephasing enhanced transport in this model.
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Dephasing enhanced transport in nonequilibrium strongly correlated quantum systems
Physical Review B, 2013Co-Authors: J J Mendozaarenas, S R Clark, T Grujic, Dieter JakschAbstract:A key insight from recent studies is that noise, such as Dephasing, can improve the efficiency of quantum transport by suppressing coherent single-particle interference effects. However, it is not yet clear whether Dephasing can enhance transport in an interacting many-body system. Here, we address this question by analyzing the transport properties of a boundary driven spinless fermion chain with nearest-neighbor interactions subject to bulk Dephasing. The many-body nonequilibrium stationary state is determined using large-scale matrix product simulations of the corresponding quantum master equation. We find Dephasing enhanced transport only in the strongly interacting regime, where it is shown to induce incoherent transitions bridging the gap between bound dark states and bands of mobile eigenstates. The generic nature of the transport enhancement is illustrated by a simple toy model, which contains the basic elements required for its emergence. Surprisingly, the effect is significant even in the linear response regime of the full system, and it is predicted to exist for any large and finite chain. The response of the system to Dephasing also establishes a signature of an underlying nonequilibrium phase transition between regimes of transport degradation and enhancement. The existence of this transition is shown not to depend on the integrability of the model considered. As a result, Dephasing enhanced transport is expected to persist in more realistic nonequilibrium strongly correlated systems.
Paola Borri - One of the best experts on this subject based on the ideXlab platform.
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spin flip limited exciton Dephasing in cdse zns colloidal quantum dots
Physical Review Letters, 2012Co-Authors: Francesco Masia, Wolfgang Werner Langbein, Nicolo Accanto, Paola BorriAbstract:The Dephasing time of the lowest bright exciton in CdSe/ZnS wurtzite quantum dots is measured from 5 to 170 K and compared with density dynamics within the exciton fine structure using a sensitive three-beam four-wave-mixing technique unaffected by spectral diffusion. Pure Dephasing via acoustic phonons dominates the initial dynamics, followed by an exponential zero-phonon line Dephasing of 109 ps at 5 K, much faster than the ∼10 ns exciton radiative lifetime. The zero-phonon line Dephasing is explained by phonon-assisted spin flip from the lowest bright state to dark-exciton states. This is confirmed by the temperature dependence of the exciton lifetime and by direct measurements of the bright-dark–exciton relaxation. Our results give an unambiguous evidence of the physical origin of the exciton Dephasing in these nanocrystals.
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Radiatively limited Dephasing in InAs quantum dots
Physical Review B, 2004Co-Authors: Wolfgang Werner Langbein, Ulrike Woggon, Paola Borri, V. Stavarache, Dirk Reuter, Andreas D. WieckAbstract:We measure the Dephasing time of the exciton ground-state transition in In1−xGaxAs quantum dots using a sensitive four-wave mixing technique. We find experimental evidence that the Dephasing time is given only by the radiative lifetime at low temperatures. We demonstrate the tunability of the radiatively limited Dephasing time from 400 ps up to 2 ns in a series of annealed In1−xGaxAs quantum dots with increasing quantum-confinement energy from 69 meV to 330 meV.
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exciton relaxation and Dephasing in quantum dot amplifiers from room to cryogenic temperature
IEEE Journal of Selected Topics in Quantum Electronics, 2002Co-Authors: Paola Borri, R L Sellin, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, D Ouyang, Dieter BimbergAbstract:We present an extensive experimental study of the exciton relaxation and Dephasing in InGaAs quantum dots (QDs) in the temperature range from 10 K to 295 K. The QDs are embedded in the active region of an electrically pumped semiconductor optical amplifier. Ultrafast four-wave mixing and differential transmission spectroscopy on the dot ground-state transition are performed with a sensitive heterodyne detection technique. The importance of the population relaxation dynamics to the Dephasing is determined as a function of injection current and temperature. Above 150 K Dephasing processes much faster than the population relaxation are present, due to both carrier-phonon scattering and Coulomb interaction with the injected carriers. Only at low temperatures (<30 K) does population relaxation of multiexcitons in the gain regime fully determine the Dephasing.
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Relaxation and Dephasing of multiexcitons in semiconductor quantum dots.
Physical review letters, 2002Co-Authors: Paola Borri, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, D Ouyang, Roman Sellin, Dieter BimbergAbstract:We measure the Dephasing time of ground-state excitonic transitions in InGaAs quantum dots under electrical injection in the temperature range from 10 to 70 K. Electrical injection into the barrier region results in a pure Dephasing of the excitonic transitions. Once the injected carriers fill the electronic ground state, the biexciton to exciton transition is probed and a correlation of the exciton and biexciton phonon scattering mechanisms is found. Additional filling of the excited states creates multiexcitons that show a fast Dephasing due to population relaxation.
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Temperature dependence homogeneous broadening and gain recovery dynamics in InGaAs quantum dots
2002Co-Authors: Paola Borri, Donald Ning Ouyang, R L Sellin, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, Dieter BimbergAbstract:We present temperature-dependent measurements of the Dephasing time in the ground-state transition of strongly-confined InGaAs quantum dots, using a highly sensitive four-wave mixing technique. At low temperature we measure a Dephasing time of several hundred picoseconds. Between 7 and 100 K the polarization decay has two distinct components resulting in a non-Lorentzian lineshape with a sharp zero-phonon line and a broad band from elastic exciton-acoustic phonon interactions. We also explore the Dephasing time beyond the one exciton occupation, by electrically injecting carriers. Electrical injection into the barrier region results in a dominantly pure Dephasing of the excitonic ground-state transition. Once the injected carriers have filled the electronic ground state, additional filling of the excited states creates multiexcitons that show a fast Dephasing due to population relaxation.
Dieter Bimberg - One of the best experts on this subject based on the ideXlab platform.
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exciton relaxation and Dephasing in quantum dot amplifiers from room to cryogenic temperature
IEEE Journal of Selected Topics in Quantum Electronics, 2002Co-Authors: Paola Borri, R L Sellin, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, D Ouyang, Dieter BimbergAbstract:We present an extensive experimental study of the exciton relaxation and Dephasing in InGaAs quantum dots (QDs) in the temperature range from 10 K to 295 K. The QDs are embedded in the active region of an electrically pumped semiconductor optical amplifier. Ultrafast four-wave mixing and differential transmission spectroscopy on the dot ground-state transition are performed with a sensitive heterodyne detection technique. The importance of the population relaxation dynamics to the Dephasing is determined as a function of injection current and temperature. Above 150 K Dephasing processes much faster than the population relaxation are present, due to both carrier-phonon scattering and Coulomb interaction with the injected carriers. Only at low temperatures (<30 K) does population relaxation of multiexcitons in the gain regime fully determine the Dephasing.
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Relaxation and Dephasing of multiexcitons in semiconductor quantum dots.
Physical review letters, 2002Co-Authors: Paola Borri, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, D Ouyang, Roman Sellin, Dieter BimbergAbstract:We measure the Dephasing time of ground-state excitonic transitions in InGaAs quantum dots under electrical injection in the temperature range from 10 to 70 K. Electrical injection into the barrier region results in a pure Dephasing of the excitonic transitions. Once the injected carriers fill the electronic ground state, the biexciton to exciton transition is probed and a correlation of the exciton and biexciton phonon scattering mechanisms is found. Additional filling of the excited states creates multiexcitons that show a fast Dephasing due to population relaxation.
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Temperature dependence homogeneous broadening and gain recovery dynamics in InGaAs quantum dots
2002Co-Authors: Paola Borri, Donald Ning Ouyang, R L Sellin, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, Dieter BimbergAbstract:We present temperature-dependent measurements of the Dephasing time in the ground-state transition of strongly-confined InGaAs quantum dots, using a highly sensitive four-wave mixing technique. At low temperature we measure a Dephasing time of several hundred picoseconds. Between 7 and 100 K the polarization decay has two distinct components resulting in a non-Lorentzian lineshape with a sharp zero-phonon line and a broad band from elastic exciton-acoustic phonon interactions. We also explore the Dephasing time beyond the one exciton occupation, by electrically injecting carriers. Electrical injection into the barrier region results in a dominantly pure Dephasing of the excitonic ground-state transition. Once the injected carriers have filled the electronic ground state, additional filling of the excited states creates multiexcitons that show a fast Dephasing due to population relaxation.
Wolfgang Werner Langbein - One of the best experts on this subject based on the ideXlab platform.
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spin flip limited exciton Dephasing in cdse zns colloidal quantum dots
Physical Review Letters, 2012Co-Authors: Francesco Masia, Wolfgang Werner Langbein, Nicolo Accanto, Paola BorriAbstract:The Dephasing time of the lowest bright exciton in CdSe/ZnS wurtzite quantum dots is measured from 5 to 170 K and compared with density dynamics within the exciton fine structure using a sensitive three-beam four-wave-mixing technique unaffected by spectral diffusion. Pure Dephasing via acoustic phonons dominates the initial dynamics, followed by an exponential zero-phonon line Dephasing of 109 ps at 5 K, much faster than the ∼10 ns exciton radiative lifetime. The zero-phonon line Dephasing is explained by phonon-assisted spin flip from the lowest bright state to dark-exciton states. This is confirmed by the temperature dependence of the exciton lifetime and by direct measurements of the bright-dark–exciton relaxation. Our results give an unambiguous evidence of the physical origin of the exciton Dephasing in these nanocrystals.
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Radiatively limited Dephasing in InAs quantum dots
Physical Review B, 2004Co-Authors: Wolfgang Werner Langbein, Ulrike Woggon, Paola Borri, V. Stavarache, Dirk Reuter, Andreas D. WieckAbstract:We measure the Dephasing time of the exciton ground-state transition in In1−xGaxAs quantum dots using a sensitive four-wave mixing technique. We find experimental evidence that the Dephasing time is given only by the radiative lifetime at low temperatures. We demonstrate the tunability of the radiatively limited Dephasing time from 400 ps up to 2 ns in a series of annealed In1−xGaxAs quantum dots with increasing quantum-confinement energy from 69 meV to 330 meV.
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exciton relaxation and Dephasing in quantum dot amplifiers from room to cryogenic temperature
IEEE Journal of Selected Topics in Quantum Electronics, 2002Co-Authors: Paola Borri, R L Sellin, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, D Ouyang, Dieter BimbergAbstract:We present an extensive experimental study of the exciton relaxation and Dephasing in InGaAs quantum dots (QDs) in the temperature range from 10 K to 295 K. The QDs are embedded in the active region of an electrically pumped semiconductor optical amplifier. Ultrafast four-wave mixing and differential transmission spectroscopy on the dot ground-state transition are performed with a sensitive heterodyne detection technique. The importance of the population relaxation dynamics to the Dephasing is determined as a function of injection current and temperature. Above 150 K Dephasing processes much faster than the population relaxation are present, due to both carrier-phonon scattering and Coulomb interaction with the injected carriers. Only at low temperatures (<30 K) does population relaxation of multiexcitons in the gain regime fully determine the Dephasing.
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Relaxation and Dephasing of multiexcitons in semiconductor quantum dots.
Physical review letters, 2002Co-Authors: Paola Borri, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, D Ouyang, Roman Sellin, Dieter BimbergAbstract:We measure the Dephasing time of ground-state excitonic transitions in InGaAs quantum dots under electrical injection in the temperature range from 10 to 70 K. Electrical injection into the barrier region results in a pure Dephasing of the excitonic transitions. Once the injected carriers fill the electronic ground state, the biexciton to exciton transition is probed and a correlation of the exciton and biexciton phonon scattering mechanisms is found. Additional filling of the excited states creates multiexcitons that show a fast Dephasing due to population relaxation.
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Temperature dependence homogeneous broadening and gain recovery dynamics in InGaAs quantum dots
2002Co-Authors: Paola Borri, Donald Ning Ouyang, R L Sellin, Ulrike Woggon, Wolfgang Werner Langbein, S. Schneider, Dieter BimbergAbstract:We present temperature-dependent measurements of the Dephasing time in the ground-state transition of strongly-confined InGaAs quantum dots, using a highly sensitive four-wave mixing technique. At low temperature we measure a Dephasing time of several hundred picoseconds. Between 7 and 100 K the polarization decay has two distinct components resulting in a non-Lorentzian lineshape with a sharp zero-phonon line and a broad band from elastic exciton-acoustic phonon interactions. We also explore the Dephasing time beyond the one exciton occupation, by electrically injecting carriers. Electrical injection into the barrier region results in a dominantly pure Dephasing of the excitonic ground-state transition. Once the injected carriers have filled the electronic ground state, additional filling of the excited states creates multiexcitons that show a fast Dephasing due to population relaxation.
