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Bennett, Alfred W.

doi:10.1038/004425c0

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“…Our samples contain dots located in the center of a p−i−n diode with Al 0.75 Ga 0.25 As barriers on either side, which allow vertical electric fields to change the FSS [20]. We observe a minimum value of FSS, |s 0 |, which varies from dot to dot.…”

Section: Pacs Numbersmentioning

confidence: 91%

“…When the FSS is reduced to the minimum value, |s 0 |, the eigenstates of the exciton are rotated to be diagonal and anti-diagonal in the laboratory frame [20] ( Figure 1c). Again, the degree of polarization from the LE measurement decays at a rather slow rate.…”

Section: Pacs Numbersmentioning

confidence: 99%

“…In turn this leads to an even smaller increase in the total splitting because the linear and circular splitting are added in quadrature. In practice, the error on the spectral measurement of FSS is greater than 0.3 µeV [20] so this difference between the temporal |s| and spectral measurement of |s linear | cannot be observed (Figure 1b). ( 2) From Figure 2c it can be seen that measurements of the free-induction decay will be different for measurements along the LS and CS axes.…”

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Free induction decay of a superposition stored in a quantum dot

et al. 2011

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We study the free evolution of a superposition initialized with high fidelity in the neutral-exciton state of a quantum dot. Read-out of the state at later times is achieved by polarized photon detection, averaged over a large number of cycles. By controlling the fine-structure splitting (FSS) of the dot with a DC electric field we show a reduction in the degree of polarization of the signal when the splitting is minimized. In analogy with the "free induction decay" observed in nuclear magnetic resonance, we attribute this to hyperfine interactions with nuclei in the semiconductor. We numerically model this effect and find good agreement with experimental studies. Our findings have implications for storage of superpositions in solid state systems, and for entangled photon pair emission protocols that require a small value of FSS. PACS numbers:Quantum effects are often masked by interactions with the environment. A well-known example is found in magnetic resonance spectroscopy. Typically, a radiofrequency pulse is used to prepare the nuclear spin states, which then precess around the applied magnetic field [1]. The signal obtained from simultaneously measuring the projection of all spins along some direction perpendicular to the field displays oscillations which appear to fall away with time in a process known as "free induction decay" (FID). In part this FID is due to the intrinsic decoherence of the spins, a so called T 2 process. But in the solid state this is often masked by a faster decay in the signal which arises from variations in the field, susceptibility and local environment of the nuclei, which consequently precess at different rates.Quantum science can now routinely probe single solid state quantum systems, such as the spin of electrons trapped at color centers in diamond [2](which has a weak phonon interaction) or single spins in silicon [3](in which the host lattice has nuclear spin zero). On the other hand III-V semiconductors have both phonon and nuclear interactions to contend with, but are nonetheless interesting for their potential scalability and miniaturization, particularly as sources of non-classical light [4,5].One of the most studied systems are single InGaAs/GaAs quantum dots as they have optically active states with well-understood selection rules, allowing spinphoton conversion [6-10] and optical control [11,12]. Interactions of these states with the nuclear spins in the quantum dot has lead to a wealth of new physics, such as "dragging" the energy of a transition as it follows a resonant laser [13,14] and nuclear-spin switching [15]. Most of the literature on the effect of nuclear spins in a quantum dot has been concerned with the spin eigenstates of the charge-exciton transition [7, 12-14, 16, 17] or in some cases the neutral exciton transition in applied external magnetic field [14,15,18]. Through this work it has been shown that the hole has a hyperfine interaction which is an order of magnitude weaker than that of the electron [17,19]. In contrast, our work is focussed on the b...

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Section: Pacs Numbersmentioning

confidence: 91%

Section: Pacs Numbersmentioning

confidence: 99%

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