Dephasing due to coupling to the external environment in open quantum-dot arrays

Elhassan, M.; Bird, J. P.; Akis, R.; Ferry, D. K.; Ida, Tetsuya; Ishibashi, Koji

doi:10.1088/0953-8984/17/33/l02

Cited by 12 publications

(11 citation statements)

References 24 publications

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“…In mesoscopic systems, the quantum phases of carrier states can be randomized by inelastic or quasi-elastic scattering mechanisms such as electron-phonon and electron-electron scattering, and quantum decoherence results [1][2][3][4]. Also,the measurement of a quantum system necessitates coupling to the external environment, considered a classical system [5,6], leading to environmental coupling decoherence [5][6][7][8]. At low temperature T, the inelastic or quasi-elastic scattering mechanisms are mitigated [5], and sufficiently long quantum phase coherence lengths φ L are obtained to study electronic transport phenomena relying on quantum interference [9,10].…”

Section: Introductionmentioning

confidence: 99%

Geometrical dependence of quantum decoherence in circular arenas with side-wires

Xie

Priol

Heremans

2016

J. Phys.: Condens. Matter

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Low-temperature quantum phase coherence lengths were experimentally measured in mesoscopic circular arenas fabricated on InGaAs quantum wells. The arenas are connected to wide sample regions by short side-wires, to investigate the effects of geometry in comparison to intrinsic materials properties on quantum decoherence. Universal conductance fluctuations were used to quantify the phase coherence lengths as a function of temperature and geometry. The experimental data show a dependence of phase coherence lengths on side-wire length and width-to-length ratio, which is accounted for by the competing effects of decoherence by coupling to the classical environment and Nyquist decoherence in ergodic wires. The observed decay of phase coherence lengths with the increasing temperature is consistent with expectations. The work demonstrates that geometrical effects influence the measured mesoscopic quantum decoherence.

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Section: Introductionmentioning

confidence: 99%

Geometrical dependence of quantum decoherence in circular arenas with side-wires

Xie

Priol

Heremans

2016

J. Phys.: Condens. Matter

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“…Finally, we identify backscattered states, which do not propagate through the system. We illustrate this with examples taken from experiments on a prototypical open quantum system, namely an open quantum dot array [5,6], which has been modeled both classically and quantum mechanically [7]. Such an array also connects to systems arising from periodic structures such as carbon nanotubes or molecules.…”

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confidence: 99%

“…2, the classical Poincaré section 2 is shown for the fourth dot in the array [5][6][7] at E = 8.41 meV and B = 0.24 T. The velocity is normalized to the Fermi velocity (2.1 × 10 5 m/s). The current-carrying states have a certain chaos-like behavior, in that they do not show Fig.…”

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Transport in open quantum systems: comparing classical and quantum phase space dynamics

et al. 2008

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Transport in open quantum systems is of great interest. We show that the discrete states of an open quantum system may be classified into three distinct groups, dependent upon the manner in which they influence transport when connected to an external environment. A first class of states is current-carrying states, which are naturally strongly connected to the environment. A second class of states is discrete, but stable and isolated, and thought to be the pointer states of decoherence theory. Finally, we identify backscattered states, which do not propagate through the system. KeywordsOpen quantum systems · Conductance · Pointer states · ResonancesThe study of open quantum systems is important to gaining an understanding of how quantum states evolve into their classical counterparts [1]. This is particularly true in nanoelectronics devices, where the decoherence and phasebreaking processes are important. Such systems are open quantum systems interacting with their environment, the latter of which may be a bath or even a measurement system. The manner in which the quantum properties are revealed by such classical measurements, as well as the manner in which these quantum properties evolve into intrinsic classical properties, has long been of interest. One interpretation, which explicitly includes the coupling of the device to its environment, is decoherence theory [2]. However, the interpretation of the decoherence process has varied widely, and is crucially dependent upon the nature of the states that can exist within the device itself.In this paper, we show that the discrete states of an isolated quantum system may be classified into three groups, dependent upon the manner in which they influence transport when the system is opened. We show first that there is a class of current-carrying states, which are strongly connected to the environment. A second class of states is found to be a discrete set of stable, and isolated, states which are thought to be the so-called pointer states of decoherence theory [3]. (We have previously shown a connection to these pointer states in transport through open quantum dots [4].) We show how some of the current-carrying states can connect to the pointer states via phase-space tunneling processes to produce Fano resonances in the transmission. Finally, we identify backscattered states, which do not propagate through the system. We illustrate this with examples taken from experiments on a prototypical open quantum system, namely an open quantum dot array [5,6], which has been modeled both classically and quantum mechanically [7]. Such an array also connects to systems arising from periodic structures such as carbon nanotubes or molecules.Usually, transport through an open system is treated via electrodes configured as large reservoirs. However, we adopt a different approach that allows us to identify the connection between the quantum states of the open and closed system. Rather than treating the reservoirs in their normal sense, we introduce complex potentials at the contact regi...

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“…In the absence of scattering within the active region, the coupling of the active region to the contacts is the cause of its nonunitary evolution (decoherence) towards a nonequilibrium steady state, and the importance of this coupling has become wellrecognized in quantum transport studies. The description and manipulation of the contact-induced decoherence are presently of great importance not only in quantum transport studies, 4,5,6,7,8,9,10,11,12 but also in the theory of measurement 13 and quantum information. 14 The purpose of this paper is to provide a simple description of the nonunitary evolution of a ballistic nanostructure's active region due to the injection of carriers from the contacts.…”

Section: Introductionmentioning

confidence: 99%

Decoherence due to contacts in ballistic nanostructures

Knežević

2008

Phys. Rev. B

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The active region of a ballistic nanostructure is an open quantum-mechanical system, whose nonunitary evolution (decoherence) towards a nonequilibrium steady state is determined by carrier injection from the contacts. The purpose of this paper is to provide a simple theoretical description of the contact-induced decoherence in ballistic nanostructures, which is established within the framework of the open systems theory. The active region's evolution in the presence of contacts is generally non-Markovian. However, if the contacts' energy relaxation due to electron-electron scattering is sufficiently fast, then the contacts can be considered memoryless on timescales coarsened over their energy relaxation time, and the evolution of the current-limiting active region can be considered Markovian. Therefore, we first derive a general Markovian map in the presence of a memoryless environment, by coarse-graining the exact short-time non-Markovian dynamics of an abstract open system over the environment memory-loss time, and we give the requirements for the validity of this map. We then introduce a model contact-active region interaction that describes carrier injection from the contacts for a generic two-terminal ballistic nanostructure. Starting from this model interaction and using the Markovian dynamics derived by coarse-graining over the effective memory-loss time of the contacts, we derive the formulas for the nonequilibrium steady-state distribution functions of the forward and backward propagating states in the nanostructure's active region. On the example of a double-barrier tunneling structure, the present approach yields an I-V curve that shows all the prominent resonant features. We address the relationship between the present approach and the Landauer-Büttiker formalism, and also briefly discuss the inclusion of scattering.

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Dephasing due to coupling to the external environment in open quantum-dot arrays

Cited by 12 publications

References 24 publications

Geometrical dependence of quantum decoherence in circular arenas with side-wires

Geometrical dependence of quantum decoherence in circular arenas with side-wires

Transport in open quantum systems: comparing classical and quantum phase space dynamics

Decoherence due to contacts in ballistic nanostructures

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