Publisher's Note: Complete disentanglement by partial pure dephasing [Phys. Rev. A<b>73</b>, 022313 (2006)]

Roszak, Katarzyna; Machnikowski, Paweł

doi:10.1103/physreva.73.029906

Cited by 42 publications

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“…Starting from an initial fully mixed state, ρ in = 1 1/4, we can allow the system to evolve governed by (10). A typical run is displayed in Fig.…”

Section: Numerical Analysismentioning

confidence: 99%

“…An important step was the realization by Jakóbczyk [8] and Yu and Eberly [9] that entanglement can reach zero in a finite time. This behavior was dubbed "entanglement sudden death" [9,10,11,12,13,14,15] and has received much recent attention. The ability of entanglement to have this non-analytic behavior can be traced back to its definition: two particles are considered entangled if their combined density matrix cannot be decomposed into a weighted sum of pure, separable density matrices.…”

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confidence: 99%

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Entanglement genesis under continuous parity measurement

Williams

Jordan

2008

Phys. Rev. A

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We examine the stochastic dynamics of entanglement for an uncoupled two-qubit system, undergoing continuous parity measurement. Starting with a fully mixed state, the entanglement is zero for a finite amount of time, when it is suddenly created, which we refer to as entanglement genesis. There can be further entanglement sudden death/birth events culminating in the formation of a fully entangled state. We present numerical investigations of this effect together with statistics of the entanglement genesis time in the weak measurement limit as well as the quantum Zeno limit. An analytic treatment of the physics is presented, aided by the derivation of a simple concurrence equation for Bell basis X-states. The probability of entanglement border crossing and mean first passage times are calculated for the case of measurement dynamics alone. We find that states with almost the same probability of entanglement border crossing can have very different average crossing times. Our results provide insights on the optimization of entanglement generation by measurement.PACS numbers: 03.65. Ta,03.65.Yz Entanglement is arguably the most fascinating aspect of quantum mechanics and plays a central role in quantum information science. The peculiar non-classical correlations which entanglement characterizes are the basis for exciting applications such as teleportation, quantum encryption, and many others [1]. Since the concept of entanglement appeared, there has been much research into its properties. One aspect of this research has been how to quantify the amount of entanglement contained in a quantum state. Many different entanglement measures have been introduced with varying degrees of success [2]. In the two qubit case, the concurrence measure of entanglement can be explicitly given in general for any mixed state [3], making this system ideal for further research.In parallel with these measures, investigations into the dynamics of entanglement began and continue still. If entanglement is to be used as a resource, then its dynamical evolution must be understood. Of particular interest is how entanglement decays when the entangled systems are coupled to the environment. It was found that entanglement typically decreases at an exponential rate, faster than single-qubit decoherence [4,5,6,7]. An important step was the realization by Jakóbczyk [8] and Yu and Eberly [9] that entanglement can reach zero in a finite time. This behavior was dubbed "entanglement sudden death" [9,10,11,12,13,14,15] and has received much recent attention. The ability of entanglement to have this non-analytic behavior can be traced back to its definition: two particles are considered entangled if their combined density matrix cannot be decomposed into a weighted sum of pure, separable density matrices. If such a decomposition can be found, then it is defined to be seperable, having zero entanglement. While it is important to understand the disappearance of entanglement, we must also understand how it is generated in the first place. This is the topic d...

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“…Starting from an initial fully mixed state, ρ in = 1 1/4, we can allow the system to evolve governed by (10). A typical run is displayed in Fig.…”

Section: Numerical Analysismentioning

confidence: 99%

mentioning

confidence: 99%

Entanglement genesis under continuous parity measurement

Williams

Jordan

2008

Phys. Rev. A

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“…Phonon wave packets emitted from one QD can modulate the optical response of a second QD [114]. Phonons in general also give rise to the decay of entanglement between excitons in two QDs [115], which is an important aspect in quantum computation.…”

Section: Quantum Dot Modelmentioning

confidence: 99%

The role of phonons for exciton and biexciton generation in an optically driven quantum dot

Reiter

Kuhn

Glässl

et al. 2014

J. Phys.: Condens. Matter

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Abstract. For many applications of semiconductor quantum dots in quantum technology a well controlled state preparation of the quantum dot states is mandatory. Since quantum dots are embedded in the semiconductor matrix, the interaction with phonons plays often a major role in the preparation process. In this review, we discuss the influence of phonons on three basically different optical excitation schemes which can be used for the preparation of exciton, biexciton, and superposition states: a resonant excitation leading to Rabi rotations in the excitonic system, an excitation with chirped pulses exploiting the effect of adiabatic rapid passage, and an off-resonant excitation giving rise to a phononassisted state preparation. We give an overview over experimental and theoretical results showing the role of the phonons and compare the performance of the schemes for state preparation.

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“…The biexcitonic shift in the absence of any decoherence processes causes a coherent oscillation between the initial, maximally entangled state, and the separable state |ψ sep = 1/2(|0 + |1 ) ⊗ (|0 + |1 ) (reached when ∆Et = (2n + 1)π, where n is a natural number). Under phonon-induced pure dephasing, the oscillations of entanglement are damped and display prolonged periods when the entanglement is zero (which is only possible when the damping process can lead to sudden death of entanglement), and are otherwise smooth while their amplitude is limited by the entanglement decay displayed by the zero-biexcitonic shift evolution [26]. The oscillations of the geometric discord, which without decoherence would mimic entanglement oscillations, are substantially different.…”

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confidence: 99%

“…[26]. Since local unitary transformations do not change the amount of quantum correlations in the system, we can use the density matrixρ(t) = e −iHLt ρ(t)e iHLt , with…”

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Anomalous decay of quantum correlations of quantum-dot qubits

2013

Self Cite

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We study the evolution of quantum correlations, quantified by the geometric discord, of two excitonic quantum dot qubits under the influence of the phonon environment. We show that the decay of these correlations differs substantially form the decay of entanglement. Instead of displaying sudden death type behavior, the geometric discord shows a tendency to undergo transitions between different types of decay, is sensitive to non-local phase factors, and may already be enhanced by weak environment-mediated interactions. Hence, two-qubit quantum correlations are more robust under decoherence processes, while showing a richer and more complex spectrum of behavior under unitary and non-unitary evolution.PACS numbers: 03.65. Ta, 63.20.Kd, 78.67.Hc The study of quantum correlations in realistic systems has, for a long time, been limited to the study of entanglement, due to the fact that straightforward methods of calculating the amount of correlations in a two-qubit system have only been available for some entanglement measures, such as the concurrence [1,2] or negativity [3,4]. Although entanglement itself is a very important resource for a number of applications [5], including quantum computation, quantum cryptography, or teleportation, separability (the lack of entanglement) does not automatically exclude the presence of quantum correlations [6]. This is in particular the reason why quantum computation models relying on mixed, separable (not entangled) states [7][8][9] are possible.The quantum discord [10, 11] is a measure of quantum correlations (see, however Refs. [11,12] for Holevo-type and thermodynamic based measures) which captures correlations beyond entanglement; it is defined as the difference of two classically equivalent formulas for mutual information and is non-negative. Due to the null volume of the set of zero-discord states [13], discord measures are not expected to undergo sudden death which is characteristic for entanglement evolutions [14][15][16]. The geometric measure of the discord describes the amount of correlations in a quantum system by finding the minimal Hilbert-Schmidt distance to the set of zero-discord states [17]. Recently, a lower [17] and an upper [18] bound on the geometric discord which can be calculated from a two-qubit density matrix have been found, which substantially simplifies the problem of studying the evolution of the quantum discord and opens the path for a qualitative and quantitative description of the decay of quantum correlations in realistic open quantum systems.In this paper we study the evolution of the lower and upper bounds of the geometric discord of two exciton quantum dot (QD) qubits interacting with an open phonon environment in order to capture the physical aspects of decoherence effects on quantum correlations. The interactions present in the system and the resulting dynamics are well understood. The experimentally observed evolution on picosecond timescales [19,20] can be described by pure dephasing within the independent boson model [20,21]. Super-Oh...

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Publisher's Note: Complete disentanglement by partial pure dephasing [Phys. Rev. A73, 022313 (2006)]

Cited by 42 publications

References 0 publications

Entanglement genesis under continuous parity measurement

Entanglement genesis under continuous parity measurement

The role of phonons for exciton and biexciton generation in an optically driven quantum dot

Anomalous decay of quantum correlations of quantum-dot qubits

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